Sourcing your grapes
Winemaking – A Handbook
Bruce W. Hagen
Contents
Basics winemaking – A Handbook 3
The basics: 3
What is winemaking?. 3
Basic differences between reds, whites and rosé wines: 3
Sanitation 5
Recommended alkaline cleaning products for winery cleaning: 6
Common sanitizers: 7
Cleaning and sanitizing your barrels: 8
Other ways to prevent microbial spoilage: 10
Using SO2 to ensure good quality wine: 12
The value of SO2: 13
Forms of SO2 ― free, bound, and total: 13
What SO2 does and why you need to and add more during winemaking process? 14
The chemistry of SO2: 14
Stages of winemaking and SO2: 16
Adding SO2 and Potassium Metabisulfite: 17
Measuring SO2: 17
Ways to add SO2: 18
Factors affecting how much SO2 is needed: 19
The winemaking process - Getting Started 20
Sourcing grapes: 20
Cellar sanitation: 20
Harvest: 20
Temperature control: 22
Testing and adjusting the juice or must: 22
Adjusting °Brix: 22
Calculating how much water to add: 23
Acidity: pH: 24
Adjusting acidity (in a nut shell): 25
Common wine acid problems table: 25
The low down on adjusting pH: 26
The most common wine acid problems: 26
Making corrections: 27
Natural pH changes during winemaking: 29
Something to keep in mind: 30
Other options: 30
Problematic grapes: 30
Acidity: TA: 30
The ‘nuts and bolts’ of Adjusting TA: 31
Stemming/crushing red and white grapes: 32
To sulfite or not to sulfite? Two options for fermenting white grapes: 33
SO2 addition: Pre-fermentation: 33
Skin contact: white and red grapes when making rosés: 34
Pressing white grapes: 34
Settling (clarifying) the pressed juice (whites): 35
Fermentation tannins for white grapes: 36
Racking (siphoning) settled juice from solids: 36
Preemptive Fining: (white juice): 37
Protein instability in white wines: 37
Other fining agents that can be added before fermentation: 38
Red grapes: Cold soaking proir tp fermentation)
Fermentation enzymes for red grapes: 39
Fermentation(sacrificial) tannins for red grapes
Fermentation: getting started 40
White grapes: 40
Red grapes:
Rehydrating yeasts and adding nutrition: both red and white grapes: 41
Adding the yeast mixture (red and white): 41
Yeast nutrition: (red and white): 42
Managing nutrient levels: 42
Other yeast-based nutrients: 45
Fermentation tannins (red and white fermentations): 45
Managing white grape fermentation: 45
Managing red grape fermentation: 46
Stuck fermentations: 47
End of primary fermentation for whites and Rosés: 48
Second SO2 addition (post fermentation ― (whites and rosés) 48
Aging wines ‘sur-lie’: 49
End of primary fermentation for red wines: 49
Extended maceration: optional 49
Pressing reds: 50
Malolactic fermentation (MLF): 51
Post MLF SO2 addition: 53
SO2 additions during storage and aging: 54
Limiting the loss/use of SO2: 54
Aging and clarification: 55
Fining: 56
Fining agents: 56
Racking: 58
Topping: 60
Pre-bottling SO2 additions: 60
Filtering: 60
Bottling: 61
Helpful numbers: conversions 61
Basic winemaking – A Handbook
Bruce Hagen
Introduction: My intent for writing ta handbook was to help me to focus on the most important aspects of winemaking, to explore a wide variety of resources for advice, explanations, recommendations, and solutions to complex problems, etc., and to serve as a guide for interested GENCO. Members. From what I can determine, the two most important and difficult aspects of winemaking are managing SO2 levels and adjusting acidity.
There is no single way to make wine, no hard and fast rules, only guidelines and some generally accepted practices that have been shown by research and experience to improve your success rate. What I’ve done is to present some of the basic, time-honored (empirical), as well as science-based practices useful in making wines that meet current commercial standards. Wine can be made without using cultured yeast, SO2, or any of the currently available fermentation aids (enzymes, tannin products, fining agents, etc., or use of high-tech equipment — if that’s what you want. But unless you really know what you’re doing, the results may be disappointing. The learning curve is long and steep. There are reasons for following accepted practices, at least loosely, and areas where you have greater flexibility to be creative, or to just let ‘nature’ do ‘her’ thing. All of our technological advancements stem from trial and error, mistakes, disappointment, problem-solving, innovation, scientific research, and the desire to make a better wine, or ‘widget’ for that matter. Some people would have you think that natural-made wines are necessarily better because they are natural, but that just isn’t so. Well, at least, I’m not buying it. The use of stainless steel and electricity are modern improvements that have proven quite useful.
The basics:
What is winemaking? Simply put, it is the art and science of making wine. To the French, though, winemakers refer to themselves vignerons or winegrowers rather than winemakers. They emphasize the cultivation of grapes for winemaking, and don’t make a distinction between growing grapes and making wine—the two are inextricably linked. Many wineries in France still use time-honored methods, but take advantage of modern technology. In other wine growing regions, like California, there are viticulturalists and enologists. Yes, many winemakers are very involved with the growing of grapes for their wines, others—not as much. There are some winemakers who strive to make wines as naturally as possible—minimal intervention. No question, they may make very fine wines that are long-lived, balanced, and often have that elusive minerality and a sense of place— terroir. While other winemakers use the latest ‘tricks to make big, bold, complex, well-structured, silky and opulent wines, but often overly alcoholic wines, unless adjusted downward using reverse osmosis. And for the most part they are very pricey. The question is what style do you want to make? So, it’s really up to you to frame your style, and adjust your winemaking accordingly.
Basic differences between reds, whites and rosé wines:
▪ The pH range for white grapes for making still wines is from about 3.0 to 3.5 and the range for reds is generally of 3.4 to about 3.8.
▪ The juice of both red and white grapes, with a few exceptions, is basically colorless. However, the pigments in skins of red grapes provide the red to blue/red color that characterize red wines.
▪ Tannins, found in both red and white grapes, are readily transferred to the wine during skin contact, particularly fermentation.
▪ In general, white grapes and red grapes used to make rosés are chilled, de-stemmed, crushed, and pressed off the skins before fermentation. They are typically pressed within a few hours of pressing of crushing to prevent tannin and/or pigment extraction. The result is a fresh, fruity, and crisp wine. Too much skin contact, however, can result in a harsh finish, or a color darker than desired. Limited skin contact, though, can enhance varietal extraction.
▪ If you are interested in the more traditional Provençal-style of rosés, which are very pale—from salmon to onion skin, you’ll need to press whole (uncrushed) clusters. The yield will be less, but you’ll get very little color. The remaining skins, which still contain juice, can be added to another red wine fermentation, if reasonably compatible for greater extraction. This works best when you’re making both a rosé and a red from the grapes. You probably wouldn’t want to add, for example, Cabernet sauvignon grape skins to fermenting Pinot noir.
▪ White grapes and rosés are best fermented near 60°F. T
▪ The ideal range for fermenting whites is about 55 to 64°F, depending on grape variety and your goal
▪ Red grapes are typically de-stemmed, crushed, ‘cold-soaked’ (optional), and the wine pressed-off the skins and seeds after fermentation. Skin contact is lengthy, so color and tannins are more intense. Red grapes should remain in contact with the juice during much of the fermentation to make reasonably pigmented red wine. Tannins are important for developing structure and protecting the wine during cellaring and in the bottle. Fermentation temperatures range between 70° and 85°F. Many red fermentations may reach 90°F or higher for a short period. Be careful, though, about keeping fermentation within their respective temperature ranges listed by the manufacturer for each specific yeast. Hot fermentations can stress the yeast or cause a fermentation to stick.
▪ Ideally, harvest grapes for Rosé wines at a lower Brix than for red wines. For the best results, pick from about 21.5 to about 23 for crisp, fresh, fruit-forward roses. They can also be made in the traditional method by draining off a portion of pink juice immediately after destemming/crushing red grapes and then fermenting the juice separately from the rest. The objective of removing some of the juice is to increase the skin-to-juice ratio of the remaining portion, so that the resulting red wine will have more intense aromas, flavor, pigments, and tannins. The French call this traditional method: saignée (to bleed). Rosès can be a useful byproduct of red winemaking, or done expressly for that style of wine.
▪ The juice of white and red grapes used for rosés is prone to oxidation, and therefore should be fermented in closed containers, e.g., stainless steel or food-grade plastic tanks made of polyethylene terephthalate or PET (the plastics used for food-grade tubs and water bottles), carboys (glass or food-grade plastic) or oak barrels, and kept under an air-lock.
▪ Red must (crushed grapes) and finished red wine, due to high levels of tannins from skin contact, are more resistant to oxidation than whites. Red grapes, after destemming and crushing, are generally fermented in open-top fermenters to allow the ‘cap’ of grapes that rises to the surface during fermentation to be ‘punched down’, back into contact with the fermenting juice below. For large tanks, where it can be hard to punch down the cap, you can also pump the juice below over the grapes, using a specialized pump and screen system, to keep the skins moist.
▪ Relatively long, slow fermentations are thought to produce the best red wines. Commercial fermentation often take from 5 to 10 days to complete, sometimes longer.
▪ It’s still important that the temperature raises to the upper limit of the yeast for a short period to get good extraction.
▪ It’s a good idea to try and cool fermenting grapes when the temperature exceeds the maximum range listed for the yeast being used.
▪ In some cases, you may have to warm the fermenting grapes to promote an active fermentation.
▪ Unless you regulate temperature most red fermentation will take 4 to 7 days to complete
▪ White grapes are typically fermented at lower (cool) temperatures to preserve varietal fruit aromas, and can take up to 2 to 3 weeks to finish, assuming the temperature is kept close to or below 60°F.
▪ Reds typically undergo a secondary (malolactic) fermentation (MLF) that reduces the wines acidity. Chardonnay wine, however, is usually inoculated with a ML bacteria culture, or allowed to undergo MLF naturally.
▪ Whites may undergo a spontaneous MLF in the storage container or bottle. Lysozyme or Stab Micro (Enartis) or a similar product from Scott Labs. Sterile filtration with a 0.45 micron (absolute) membrane filter also prevent MLF in the bottle.
Sanitation
If you’re like most home winemakers, you probably don’t clean and sanitize your equipment the way you should, or as often as you should throughout the winemaking process. That oversight can lead to spoilage problems with your wine. Careful attention to cleanliness and detail will minimize potential problems.
Commercial wineries take cleaning and sanitation very seriously. They have strict protocols for doing both with all their winemaking equipment at the end of each cycle, and at the start of a new one. A lapse in sanitation can have significant impact on the quality and marketability of the final product. And they are usually fastidious about preventing accidental introduction of spoilage organisms during crush, cold-soaking of grapes, fermentation, extended maceration, MLF, or later during racking, topping-up, pumping, filtering, and bottling.
Cleaning involves the removal of both inorganic and organic substances from the surfaces of winery equipment. Sanitation, on the other hand, is the reduction of microbes that can cause wine defects. It is not the same as sterilization and disinfection. Both of which are quite difficult to achieve.
Water quality can be an issue in winemaking. Most municipal water that has been properly treated to keep microorganism below harmful levels is fine for rinsing. Well-water, however, may contain high levels or bacteria that could affect your wine unless properly treated. Water that has been softened, pH adjusted, UV treated, and filtered is generally fine for rinsing. Soft water, though, may leave a residue and is not good to use for diluting must or mixing with yeast and other wine additives, e.g., yeast nutrients, enzymes, tannins, bentonite, etc. It also has a higher sodium level that can make a wine taste salty. Bottled water that has been filtered and is chlorine-free is much better to use for dilution and mixing with yeast and wine-making additives.
Sanitation begins with keeping your cellar reasonably clean, free of debris, and all working surfaces clean and regularly sanitized. Even floors should be vacuumed and moped with a disinfectant, especially at the start of crush. Wild yeast and bacteria are all around us—in the air, on work surfaces, on your winemaking equipment, on our clothes, and even our hands. It’s not easy or even necessary to remove or kill every bacterium or wild yeast cell that might cause spoilage. It is important, though, to keep their numbers low to minimize development and the production of metabolites that create off-aroma and flavors.
In general, anything that comes in contact with harvested grapes, juice, and wine should be cleaned and sanitized, including your hands, which are a great source of microorganisms such as lactic acid bacteria. There isn’t much that can be done to eliminate wild yeast and bacteria on grapes, but winemakers can pick into lugs or buckets that have been cleaned of surface debris, dirt and stains. From that point on, grapes should be transported in clean and sanitized containers. Stemmer crushers, presses and tanks, open-top fermenters, etc., should be thoroughly cleaned and sanitized. Collection buckets, funnels, car boys, stoppers, bungs, stir rods, tools used to punch downs, or stir the lees, etc., need to be clean and relatively sanitary. Literally everything that the grapes will come into contact with needs to be cleaned and sanitized.
Simply rinsing winery equipment such as siphon hoses and carboys after use does not remove all of the organic material, staining, and hard to see films associated with microorganisms. Alkaline cleaning agent (see below) are recommended to remove organic material, staining and biofilms (a slimy material containing microbes and polysaccharides) that are typically not visible. Molds often grow in the residual rinse water usually containing a tiny amount of wine residue, remaining after a quick rinse. It usually take r 4 rinses to remove the residue in carboys, fermenters, tanks, gallon jugs, etc. Unless, removed, it may contaminate the next batch of wine. To prevent this, use a cleaning solution, followed by a sanitizer: Star San, SaniClean or Iodine-based sanitizers such as Iodophor BMP or Io Star, a 10% solution of PMBS or high proof ethanol. Some cleaning agents can sanitize as well, after adequate contact time, but still need to be rinsed. Scrubbing may be needed to remove stubborn residue and deposits. Avoid abrasive scrubbing pads on plastic to prevent scratching. Scratched and roughened surfaces are more difficult to clean and sanitize. Cleaned and sanitized containers like carboys and beer kegs should be allowed to drain upside down until there is no visible water. Once dry, they can be stored with a paper cup inverted over the neck of the bottle, or a wadded paper towel placed in the bung hole. Other containers can be stored with the cover in place.
Recommended alkaline cleaning agents:
• Sodium carbonate (also called Soda ash): a good cleaning agent for many surfaces, but should not be used to clean barrels because it leaches key oak compounds.
• Sodium percarbonate (Sodium carbonate peroxhydrate): a bleaching agent made by combining Sodium carbonate and hydrogen peroxide. When added to water it releases hydrogen peroxide, resulting in a foaming action. It is sold as Proxycarb or PeroxyClean. It has the advantage of dissolving tartrates and neutralizing acetic acid in problem barrels.
• OxyClean- Free (no fragrances added!) Contains sodium carbonate and sodium percarbonate, sodium metasillicate, and a surfactant. Good winery cleaner and sanitizer.
• One-Step-No Rinse (contains sodium carbonate and sodium percarbonate). Cleans and sanitizes. Requires two minutes of contact time, and no rinsing required! Use 1 tablespoon per gallon of water.
• Powdered Brewery Wash, (B-Bright, Straight A ̶ special formulations): contain sodium percarbonate, sodium metasillicate, and a surfactant. They are safer than caustic cleaners and outperform them. Use 1 ounce per gallon for winery equipment. Soak equipment overnight in a PBW solution, and rinse the following morning - no scrubbing required. PBW can effectively clean items that can't be reached with a brush or sponge, and is strong enough to remove thick, difficult, caked-on organic soils. These cleaners also work well to remove labels from commercial wine bottles.
• Cleanskin-K (Scott: is an alkaline detergent. This potassium carbonate-based formulation also contains a proprietary percarbonate, chelating and sequestering agents for enhanced cleaning. Cleanskin-K efficiently removes wine tartar, color, proteins and organic soil.
• Destainex (Scott) a sodium percarbonate-based cleaning agent with sanitizing abilities, removes wine stains, protein stains, mold, mildew, and biofilms from surfaces that wine will come into contact with. Can be used on stainless steel, concrete, polyethylene, polypropylene, plastics, flexible hoses, glass and other surfaces.
• Oak Restorer-CW (Scott):: a blend of buffered carbonate, bicarbonate and proprietary surfactants. It removes tartrate crystals, wine color, protein and organic soils from barrels using cool water (68-86°F).
• TDC is a liquid acid cleaner for glass carboys and other glassware. It is unscented and comes in liquid form. Use at the rate of 1/2 Tbs. per 5 gallons of water and rinse thoroughly.
• Never use dish soaps! They are very hard to rinse out and have an added fragrance that can taint wine that comes into contact with it.
Recommended sanitizers:
• Star San is a common ‘no-rinse’ sanitizer for winery use. It’s made to foam, so it’s ideal for most general sanitizing duties (ex: tanks and equipment, etc.)
• SaniClean is similar to Star San, but has a low-foaming formulation — ideal for sanitizing pumps, filters, and as a final acid rinse.
• Both of the above products are acid-based sanitizers and when used at their recommended concentrations are quick, odorless, tasteless and safe for glass, stainless, and plastic materials. They also don’t need to be rinsed. When using Star San and Sani Clean there are no fumes and intermittent skin contact is not an issue.
• Ethanol: is also a good sanitizer. You can purchase high-proof ‘Everclear’ or Diesel vodka to use as a surface sanitizer.
• IO Star Iodine sanitizer: a ‘no rinse’ product used at the rate of 1 ounce per 5 gallons of water (25 ppm). Allow 1 minute of contact time to effectively sanitize equipment. Although, it has the same benefits as Star San and SaniClean there is a potential to stain vinyl tubing and plastic parts over time.
• BTF Iodophor: a ‘no rinse’ sanitizer for most equipment: buckets, kegs, tanks, vats, bottles and more. No residual taste or odor left behind, low foaming and gentle on hand. No-rinse concentrate requires only 1 tsp per 1.5 gallons of cool water (12.5ppm concentration) and 2 minutes of contact time to be effective.
• Alpet D2: Like Star San and SaniClean, Alpet D2 is a surface sanitizer. However, because Alpet D2 contains QUAT (a residual bacterial killer) it has the added benefit of keeping a surface sanitized even when dry. It’s ideal for sanitizing work areas where yeast and bacteria are handled and winemaking additions are weighed and made-up.
Chlorox (Sodium hypochlorite), although a good bleaching agent and sanitizer, it should never be used in the cellar or to clean or sanitize winemaking equipment. There is a real potential to cause a serious TCA taint (2, 4, 6-trichloroanisole) to wine that comes in contact with surfaces that have been cleaned with products containing hypochlorite (chlorine bleach). Don't use hypochlorite anywhere in the winery or where wine is made, aged in barrels, stored in case boxes, or areas where bags of corks or wine-making supplies are kept. There is a significant threat of taint from using a hypochlorite solution or its vapors that contact wood, wood pallets, paper, or cardboard, could conceivably come in contact with wine, case boxes or equipment used in wine-making.
Cleaning and sanitizing oak barrels:
▪ Acidify a new barrel once it has been filled with water and no longer leaks. Change water daily until the swelling is complete, or add Potassium Metabisulfite to retard spoilage. Add about 35 ppm per gal of water. (see Using Sulphur Dioxide to ensure wine stability below). Citric acid, because of its low pH, is an effective antimicrobial. Use 10 g or slightly more than1T (15g) of Citric acid per 5 gal of water. After sloshing the solution around the barrel, allow it drain out, rinse with clean water, and then fill the barrel with wine.
▪ After racking: rinse thoroughly and acidify with a Citric acid solution (10g to 5 gal of water. Slosh, drain, rinse, and fill with wine.
▪ Preparing a barrel for storage after bottling — rinse, steam clean, or if you have access to hot water use, fill with the barrel and allow it to stand for several hours to remove tartrate deposits, then drain and acidify. If you don’t have hot water, remove the tartrates use Proxycarb at the rate of 7.5 g/gal of capacity. Fill the barrel part way and add the Proxycarb and then fill the barrel to the top. Allow the solution to remain in the barrel for to several hours. If the barrel has VA (volatile acidity), double the amount of Proxycarb and leave for 24-48 hours.
▪ Another approach is to fill the barrel little over half way with water and then reduce the amount of proxycarb by half. Allow the solution to work for about an hour and then rotate the barrel—to treat the other half -- yes a bung is required.
▪ Drain and rinse the barrel several times with water. Re-acidify the barrel using 10g or 2 tsp per 5gal of rinse solution. Slosh this all around and drain completely. Next, prepare the barrel for either long term, or short term, storage.
▪ For short-term storage: after cleaning clean, fill with water and then add 40g gram of citric acid and 80 grams of PMBS to a 60-gallon barrel filled with water.
▪ Long term ‘dry’ storage: When a barrel has been cleaned and will not be refilled for an extended period, it can be stored ‘dry’. Once it has been cleaned, rinsed and acidified and drained upside down overnight. Burn a sulfur strip or disc in the barre. Be careful to avoid dropping the wick or disc inside the barrel. It’s a good idea to use a special sulfur ‘cage’ to prevent dropping the burning wick/disc, or splattering inside the barrel. Any droplets of sulfur in the barrel will result in a H2S problem during the next cycle. Burn a sulfur wick or disc every 4 to 6 weeks until barrel is dry. It usually takes burning 2 wicks until the barrels is sufficiently dry and VA organisms are unable to metabolize nutrients in the barrel. The standard dosage of sulfur is roughly 1/3 of a sulfur stick per 60-gallon barrel - roughly a 1” x 2-3” piece or a 5g disc (pastille). Avoid storing barrels outside or in open areas where boring beetles, such as the destructive lead cable borer can burrow into the wood. This is a very real issue!
▪ After dry storage, add water to swell the barrel. Turn the barrel on end and add water slowly, allowing it to trickle in. This will gradually rehydrate the heads and ends of the staves. You can minimize water use by soaking the barrel on end in a wide tub—such as a stock tank. After about 4 hrs. turn the barrel over and repeat. Once the ends no longer leak, turn the barrel on its side and begin filling slowly. It may take a while to fill the barrel because it may lose water nearly as fast as it is added. But within a couple of hours, it should retain most of the water. Typically, most leakage stops within about 8 hrs. Some leaks may take as long as 48 hours to stop. Barrels with persistent leaks should be carefully inspected and repaired as needed by a cooperage company, for example, ReCoop, a barrel repair and reconditioning company in Sebastopol. Continued leaking may be the result of small ‘bore’ holes made by the lead cable borers, usually in the groove where the head and staves meet, or at the edge of the metal hoops. You can use a wood matchstick or round tooth pick to plug the hole, or obtain a ‘spiel’ (special plug) from the Beverage People or ReCoop. I’ve had good luck stopping leaks by using barrel (bees’) wax. The wax can be used to seal ‘matchstick’ plugs. I usually melt the wax using a propane torch, allowing it to plug areas where there is persistent seepage. Mark the leaks and allow the barrel to dry overnight. You can expose the barrel to direct sunlight or use a hair dryer to expedite drying and then seal the leak or leaky area with wax. It’s a good idea to add PMBS and Citric acid to the barrel while it is filled with water for more than 24 hours to discourage spoilage bacteria.
▪ Long term storage: some winemakers prefer to store their barrels with a holding-solution when not filled with wine. This prevents the wood from drying and shrinking, and potential leaage after the barrel is rehydrated. The downside is that it leaches some of the flavor and aroma components from the barrel reducing its effective life span. This is a not an issue if you prefer neutral barrels and use other means to add oak flavors.
o Option 1: fill the cleaned barrel with water and add 4 g or 1 tsp of citric acid and 6 g (1.5 tsp) of KPMB for each gallon. For example, for a 60-gal barrel add 240g citric acid 360 g KMBS. Dissolve the chemicals in one gallon of warm water. Fill the barrel two-thirds with water, add the holding solution, top up the barrel with water, and insert the bung. Top the barrel with a holding solution monthly to replace solution lost by evaporation and absorption into the wood. The barrel can be stored indefinitely without risk of spoilage. During storage, rotate the barrel 45° in either direction every time you top up to keep the bung area soaked. Rinse away or mop any spillage or leakage to prevent etching of concrete.
o Long term storage, option 2: Pickling solution: Add 5 –10-gal water to barrel + 180g KMBS + 160 g citric acid and then bung tightly, replace every 3 to 6 months. This pickling solution creates a gas that prevents micro-organisms from growing, and the humidity inside is adequate to keep the barrel hydrated. Label barrels containing solution and be careful when opening and avoid inhaling the gas that can be very caustic if inhaled.
▪ Mitigating VA or other spoilage problem: Barrels that have a medicinal, band-aid, barnyard, horse stable, sweaty-saddle, rancid, or smoky smell are probably infected by the wild yeast Brettanomyces. Such barrels should be discarded because they can’t be cleaned easily, and is no longer suitable for holding wine. Barrel that smells of VA or have slightly off aromas can be treated with Proxycarb (4 g per gal of barrel capacity). Allow the cleaning solution to stand for 8 to 24 hours, depending on severity of problem. You can use up to 12g /gal for more serious or persistent problems. Top up the barrel after mixing the solution.
▪ Drain the barrel after soaking and neutralize the remaining alkaline residues with a citric acid solution. To prepare the solution, dissolve 4g of citric acid powder for each gallon of water. Slosh 1 to 5 gal of the citric acid solution around the barrel. Drain, rinse and check for off odors. If the barrel doesn’t smell clean, repeat the treatment as required. Fill the ‘cleaned’ barrel with wine within a few hours.
▪ It may be more prudent to discard a barrel with a serious spoilage problem, because it may affect the wine you put in it.
▪ If the barrel will not be filled within 8 hours, burn a sulfur wick or disc in the barrel for about 1 to 2 minutes in the barrel to generate some SO2 gas, preventing bacterial spoilage.
▪ Cleaning the exterior of mold-covered barrels: apply a solution of PMBS and citric acid in water (3T of each in 1 gal of water).
Other ways to prevent microbial spoilage:
▪ Pick grapes into clean picking lugs, buckets, or macrobins. Use an alkaline cleaning agent, such as Proxycarb or PBW and rinse thoroughly.
▪ Wash your hands thoroughly when handling sanitized equipment and before contacting juice or wine.
▪ Do your best to clean your cellar and sanitize work surfaces.
▪ Clean and sanitize all winemaking equipment used in the winemaking process.
▪ Use the recommended rate of SO2 (35 to 50ppm) after stemming/crushing reds or pressing whites. SO2 is a strong antimicrobial agent that kills or greatly inhibits most bacteria and wild yeasts that impart off aromas.
▪ Add winemaking products using a freshly sanitized transfer spoon and/or container (beaker) when adding the material or making a solution.
▪ Use a fresh piece of wax paper to hold a chemical or material when weighing it. You can lift the paper carefully and slide the material into a clean and sanitized mixing container.
▪ Use bottled (filtered) water to solubilize winemaking products and dilute must.
▪ Use yeast nutrients to ensure that your fermentation progresses to dryness, and does not become sluggish or stick (stop before all of the fermentable sugar is gone). Wines that are sluggish or that stick are prone to oxidation and spoilage due to low SO2 levels.
▪ When doing a cold soak, make sure the temperature of the must is reduced to less than 50 °F as quickly as possible by using dry ice or frozen water-filled plastic jugs. Yes, you have to clean and sanitize the plastic jugs.
▪ Maintaining adequate levels of SO2 throughout the entire process will usually ensure a defect-free wine.
▪ Adjusting pH levels of finished reds to less than 3.85 and 3.5 for finished whites, make them more stable.
▪ Keep open-top fermenters covered during fermentation to exclude fruit flies. They carry acetobacter bacteria.
▪ Rinse your punch-down tool after each use and sanitize it before use.
▪ Keep head-space to a bare minimum in storage containers, e.g., tanks, beer kegs, or carboys. You may need to blend in another variety if you don’t have quite enough to top-up the container.
▪ Make sure barrels are tightly bunged. You should hear a ‘woosh’ sound when you break the vacuum that forms when wine evaporates from the barrel, as you remove the bung.
▪ ‘Top’ barrels every couple of weeks, or at the very least, monthly, and use an inert gas (preferably, Argon) to minimize contact with air. Excess headspace increases the loss of SO2 (volatilization) into the head space. This is lost as soon as you open the bung. Acetobacter bacteria and film yeast (characterized as a white film on the wine’s surface) are more likely to develop when there is ample head space, the SO2 levels are low, and when oxygen is able to enter through a poorly seated bung or leaks in the barrel.
▪ Use a good quality wine to top with, preferably additional wine of the same variety. If you have extra wine, bottle some of it, say a case or two, after it has gone through MLF and has been racked. You can use it for topping a barrel as needed, instead of breaking down containers as you need the wine. An older vintage or a compatible varietal, as long as it smells and tastes OK will work. Another option is to buy an acceptably good wine like ‘Two Buck Chuck’ to top with. If you buy a wine make sure that there are no noticeable flaws.
▪ For best results, store wines at 60°F or less, because spoilage organisms are less likely to develop. If you can’t do this, make sure that your SO2 levels are adequate and you test for free-SO2 regularly and adjust as needed to maintain a level high enough to prevent oxidation and inhibit spoilage bacteria.
▪ When cleaning stainless fermenters after fermentation, pay particular attention to the inside surfaces, particularly the upper surface of the tank. Use a brush to make sure the thick residue of yeast and other metabolites that may accumulates there during fermentation, is loosened and then rinsed away. You can also turn the sealed drum on end, so the cleaning solution remains in contact with the residue for 24 hrs or longer to ensure adequate cleaning.
▪ Check your SO2 level following each racking. You’ll probably lose 10 to 15 ppm of FSO2 during racking, so you will need to add more SO2 to compensate for the amount that is lost to volatilization, and to bind up with metabolites that form when the wine is exposed to air.
▪ Contrary to conventional thinking, wines with a pH greater than 3.6 only need about 30 ppm for stability. Use the standard molecular SO2 levels for wines with a pH of 3.6 and below.
▪ Clean and sterilize your bottle filler before using, and make sure your siphon hose is sanitized.
▪ Sanitize the cork compression and insertion mechanism to prevent contaminating the corks and the wine. Spray with a solution of Star-San, a 10% PMBS sol or high-proof alcohol, etc. If you drop a cork on the floor, be sure to sanitize it before inserting it into a bottle.
▪ Keep your corks in sealed plastic bags and avoid handling them with your bare hands. Use disposable food-service or surgical-type gloves. At the very least, wash your hands thoroughly and refrain from touching your face or other parts to avoid contaminating them with Lactobacillus bacteria, commonly found on skin. It may be good for cheese-making but not wine!
▪ Before using a pump to transfer your wine, circulate a solution of a sanitizing agent like Star San through it for a minute or two. Even when carefully rinsed, pumps will contain some water and wine residue.
▪ A pressure washer is very effective at cleaning large equipment, such as open-top fermenters, macrobins, stemmer crushers and presses. You can add a cleaner to the spray water for better cleaning.
Using SO2 (Sulphur dioxide) to ensure wine stability:
I’ve included a lengthy and perhaps daunting discussion below for the serious-minded winemakers about the importance of adding and managing levels of SO2 or Sulfites during winemaking. Sulfites smell like a lit match, while sulfides are stinky.
For most amateurs, the use of SO2 is fundamental to successful winemaking. Since the 18th century, SO2 has been one of the most commonly used wine additives because of its antimicrobial and anti-oxidative properties. When used properly and in moderation, SO2 is an effective wine preservative and stabilizer. Although some wineries can make some reasonably good wines without adding SO2, using just a little of it. It’s rather unlikely that amateurs can do so without expert guidance and some pricey equipment.
Winemaking is fairly straight forward, once you understand what SO2 does, how much is needed, when to add it, and how to keep levels just high enough to protect your wine. It does require periodic monitoring and testing to know when more is needed. SO2 can be added by using Potassium Metabisulfite (PMBS) in the powder form, in a water-based solution, or as effervescent granules or tablets. Avoid the use of Sodium Metabisulfite.
The value of SO2:
▪ SO2 preserves a wine’s freshness and fruity character by virtue of its antioxidative, anti-enzymatic (prevents browning), and antimicrobial properties.
▪ SO2, when added to juice, must, finished wine, inhibits spoilage microorganisms, inactivates enzymes that cause browning of the juice, prevents oxidative browning, and the natural formation of acetaldehydes when alcohol in a wine is exposed to oxygen. Aldehydes which have a sherry-like aroma are the precursors to volatile acidity (VA) – ethyl acetate (nail polish remover), vinegar, and other off-odors.
▪ When present in sufficient amounts, it binds with aldehydes produced during fermentation and aging SO2, preventing oxidized aromas from developing. Furthermore, it reacts with Oxygen (O2) to prevent the formation of hydrogen peroxide, which in turn reacts with alcohol, forming acetaldehyde. Aldehydes, when bound with SO2, are not noticeable.
▪ Every time you open a container of wine to add something, smell or taste it, rack (remove the sediment), or top it up, you expose the wine to oxygen. If the level of SO2 in the wine is too low, the aldehydes that form will remain unbound and off-aromas will develop. If nothing is done to bind up the aldehydes, the wine may be ruined.
▪ Wines in oak barrels are exposed to small amounts of oxygen because the wood is slightly porous.
▪ Wines when exposed to air through racking, leaky bungs, leaky barrel or just past the seal of a wine tank, favors the development of acetobacter (bacteria that produce vinegar). These bacteria can develop when there is too little free-SO2 to inhibit them.
▪ Wines with little or no SO2 typically:
▪ tend to oxidize quickly —whites become more golden to brown, and reds turn brick-red to brown.
▪ lose flavor and aromas (‘flatten’)
▪ develop a sherry-like aroma (acetaldehyde) or notes of vinegar or ethyl acetate (acetone).
▪ are more susceptible to wine-spoilage organisms, e.g., Acetobacter, Lactobacillus, Brettanomyces, Pediococcus, film yeasts, and others that can impart disagreeable odors and tastes, e.g., sherry, vinegar, nail-polish remover, leathery, earthy, barnyard, medicinal, band aid, rancidity, horse-sweat, mousey, dirty sweat-socks, cheesy, sauerkraut, earthy, ‘tanky’, etc.
Forms of SO2 ― free, bound, and total:
▪ A portion of the SO2 added to juice, must, or wine binds up quickly with various grape components, and thus, referred to as bound SO2. The remaining ‘free’ portion is available to perform its important work. SO2 testing measures free SO2. Testing can also measure the ‘total’. By recording each addition, you can keep track of how much has been added. The ‘tested’ total, however, is not the same as the amount that has been added, as some is lost during fermentation and aging. ‘Bound’ SO2 is the portion that is still present, but largely unavailable to do work. Some SO2 is lost to the environment as SO2 gas, or binds with the sediment that is removed during racking. ‘Total’, therefore, is the sum of the free and bound SO2 in a wine that has finished primary fermentation and MLF (if initiated), or racking. In general, home winemakers need only be concerned about free SO2 in their wines. The concept is to add as little SO2 as possible, yet provide adequate protection of your wine.
Why must you continue adding SO2 during the wine-making process?
▪ It exists in both active (free) and inactive (bound) forms. Once bound, though, SO2 is generally inactive and doesn’t protect your wine – its work is basically done. Some of it, though, may become free later and bind with acetaldehyde.
▪ Some free SO2 is used up every time you rack a wine, or just remove the bung to smell it, taste it, or add something to it, because you expose the wine to O2.
▪ Eventually the wine becomes unstable because there is too little remaining free SO2 to prevent oxidation or inhibit bacteria.
▪ Most of the SO2 you add prior to fermentation is used up (bound) or lost to the atmosphere during fermentation. Some is lost to volatilization and precipitation in the sediment.
▪ Total SO2 measured in a wine is typically less than what has been added from start to finish.
The chemistry of SO2:
▪ Potassium metabisulfite (PMBS), when added to must, juice, or wine, releases:
o primarily bisulfite (HSO3-) ions,
o a small amount of SO2 (dissolved Sulphur dioxide gas), and
o an even smaller amount of Sulfite ions (SO32-).
▪ The pH of the solution determines how much of each is available. The reaction is as follows:
K2S2O5 (PMBS) + H2O (juice, must, wine) → 2K+ + 2(HSO3-) (bisulfite)
HSO3- + H+ ↔ SO2 (molecular form) + H2O ↔ 2H+ + SO3 2- (sulfite)
▪ Bisulfite (HSO3-) Most of the SO2 added to wine exists as bisulfite ions that don’t prevent oxidation. Nonetheless, they are still very important because they bind with acetaldehyde (the precursor of acetic acid) that forms when alcohol in wine is when exposed to air.
▪ SO2 — the molecular form, exists as a gas dissolved in water, much like Carbon Dioxide (CO2) in water. The level can be as high as 6% for a wine with a pH of 3.0 and 0.5 percent for a wine with a pH of 4.0. It has powerful antimicrobial properties, inhibiting bacteria, wild yeasts, and malolactic bacteria, and others that cause spoilage.
▪ SO3 -2 Sulfite —the amount in wine is extremely small, except at high pH. But sulfite is important even in minute amounts, because it can deactivate enzymes that cause browning and remove free oxygen from wine. In this reaction, O2 reacts with a phenolic compound, and is converted to hydrogen peroxide (H2O2). Hydrogen peroxide, as previously mentioned reacts with alcohol, forming acetaldehyde. If free sulfur dioxide is present, the hydrogen peroxide reacts with sulfite, resulting in the formation of Sulfate and water: SO32- + H2O2 → SO42- (Sulfate ion) + H2O
▪ When wine oxidizes in the presence of adequate SO2, the production of H+ causes the pH to decrease and the titratable acidity to increase, as sulfite ions are used up. This effect is small but it can be significant in high pH wines and a reduction of as much as 0.1 pH is often observed when high pH red wines are aged in barrels for a year or more.
▪ SO2 is in a pH-dependent equilibrium in juice or wine:
SO2 (molecular) + H2O ↔ H+ + HSO3- (bisulfite) ↔ 2H+ SO32- (sulfite)
▪ Although there is equilibrium between the 3 types of ions, the amounts are unequal and pH-dependent. For example, the lower the pH, the higher the percentage of molecular SO2. The level of SO2 decreases sharply with increasing pH.
[pic]
Figure 1. Shows how the amount of bisulfite, SO2 and sulfite present in a solution as pH changes.
▪ Equilibrium can shift from left to right or right to left in wine, depending on what component is being bound up.. For example, if bisulfite (HSO3-) binds up with Potassium ions, some of the SO2 present will shift back to bisulfite ions and some of the sulfite (SO32-) converts back to bisulfite until equilibrium is reestablished.
Ensuring adequate levels of SO2:
▪ The level of free SO2 in wine is measured in parts per million (ppm). However, only a portion of it is ‘active’— in the molecular form. To protect your wine against oxidation, you will have target a specific free SO2 to ensure there is enough of the molecular SO2 to do the job. That determination, however, will be dependent on pH of the juice, must, or wine.
▪ The molecular level reflects the amount of free-SO2 needed to protect juice, must, or wine with a specific pH.
▪ White grapes need a higher molecular level of SO2 than reds. Research has demonstrated that a level of 0.8 ppm (mg/L) of SO2 will adequately protect white wines during winemaking, storage, and later in the bottle. Reds, on the other hand, which contain more tannins (natural antioxidants), need a molecular level of only 0.5 ppm of SO2.
▪ As a rule of thumb, target a free-SO2 level listed in the tables below, for the type of wine (red or white) and pH. Most wineries, deviate from this rule and add less SO2 listed in the charts for reds with a pH of 3.6 or greater. The new thinking is that red wines with a pH greater than 3.6 only need about 30 ppm for stability. Many wineries maintain a free SO2 of 20 to 30 ppm for their reds with higher pHs. To be on the safe side, home winemakers should consider using 35 to 40 ppm for wines with a pH of 3.6 or higher.
|pH |0.8 ppm |0.5 ppm |
| |White Wine |Red Wine |
|2.9 |11 ppm |7 ppm |
|3.0 |13 |8 |
|3.1 |16 |10 |
|3.2 |21 |13 |
|3.3 |26 |16 |
|3.4 |32 |20 |
|3.5 |40 |25 |
|3.6 |50 |31* |
|3.7 |63 |39* |
|3.8 |79 |49* |
▪ The table above list the level of free-SO2 needed to keep a wine from oxidizing. Notice that the number goes up with pH to a point. So, it generally takes more SO2 to keep a higher pH wine safe from oxidation and bacterial spoilage than a lower pH wine.
▪ You will need to add SO2 several time during the course of winemaking: before and/or after fermentation or Malolactic fermentation (MLF), during cellaring, and just before bottling because it gradually dissipates. That’s why testing is so important during the process. Every time you rack a wine, open the container to smell the wine, taste it, or add something, you expose it to oxygen, and free SO2 is used up. Most or all of the SO2 you add prior to fermentation is used up (bound) or lost to the atmosphere during fermentation.
Molecular SO2 needed for Stability (ppm)
White and Rosé wines: try to maintain a 0.8 molecular SO2 level throughout the winemaking process, except for wines that will undergo MLF, and keep the pH below 3.6. For example, to ensure that there is 0.8ppm of molecular SO2 in a white wine with a pH of 3.4, you’ll need to add 32ppm of SO2
[pic]
Red wines: free-SO2 needed for a 0.5 ppm molecular level.
Free-SO2 needed for a 0.5ppm molecular level:
pH SO2 ppm or mg/l
3.4 20
3.5 25
3.6 30 ppm. At 3.6 and higher to a point the wine is protected by some other means*.
3.7
3.85
*Contrary to older charts, wines with a pH of 3.6 and above need less free SO2. Clark Smith (Vinovation, and WineSmith. Personal communication). Above 3.6 SO2 binds with H2O2, a precursor of acetaldehyde, forming H2SO4 (sulfuric acid) which increases acidity. Why less SO2 is needed as pH increases above 3.6 is not understood.
Red wines much above 3.85 are likely to be unstable and should be acidified to lower the pH. pH and TA is best adjusted before or just after fermentation (see Testing and Adjusting the Must below).
Other considerations:
▪ To ensure that the free-SO2 levels remains near the required level between additions, add an additional 10 to 15 ppm. Thus, maintaining the SO2 level for reds at about 45 ppm will ensure that your wine is adequately protected as the SO2 level dissipates.
▪ Lower pH wines are inherently more stable because they need less SO2 for protection and provide a less favorable environment for spoilage organisms.
▪ Lower pH wines are generally more acidic, brighter and sometimes fruitier, while higher pH wines are softer, smoother, but sometimes flat. For red wines, a final pH of 3.7 to 3.75 is good. It’s a good idea to do trials to see how the wine tastes at different levels of pH.
▪ Many commercial winemakers use a more moderate approach when making SO2 additions. They can do so because they have more options and greater control over the wine-making process than home winemakers.
Stages of winemaking and SO2:
Pre-fermentation: The initial SO2 addition is typically done immediately after crushing or just following pressing, and before yeast inoculation. In general, the recommended amount after crushing is usually 30 to 50 parts per million(ppm) :about 2 grams of potassium metabisulfite per five gallons of juice, or approximately one gram per 40 pounds of fruit).
To reduce the amount of SO2 used, some winemakers add the SO2 after the fermentation is done (see To sulfite or not to sulfite? Two options for fermenting grapes use to make white, rosé wines, below.
▪ Fermentation: once the initial dose of SO2 has been made, it is not necessary or beneficial to add any more until after the fermentation is finished.
▪ Post-fermentation: Wines, having completed their primary (alcoholic) or secondary (malolactic) fermentation are very susceptible to oxidation and bacterial spoilage. Therefore, a second timely addition is needed to keep them stable. Most white wines and rosés will need more SO2 (at least 50ppm) shortly after fermentation. Reds, with a few exceptions, and traditional chardonnays, however, should not receive any further SO2 until they have completed malolactic fermentation (MLF). Wait until the MLF is done before making a second addition to avoid inhibiting ML bacteria.
▪ During settling, after racking and aging: SO2 levels will continue to drop throughout the winemaking process. Every time you rack or open the container to smell, taste, or to add something, you expose the wine to air, and SO2 dissipates. Barrel aging also exposes the wine to small amounts of air. It’s critical to monitor the SO2 level and adjust periodically to maintain sufficient free-SO2 to maintain the needed molecular SO2 level. To ensure that the SO2 level remains near the desired level between additions, add an additional 10 to 15 ppm. Maintaining the SO2 level at about 45 ppm wines) will safeguard most wine. Containers should be kept filled, so there is little or no head-space. This is particularly important for barrels because they lose quite a bit of wine due to evaporation. It’s also prudent to purge the air space in a container, even when it’s small, with inert gas before resealing it. Check the SO2 levels at preferably monthly. At some point, the wine, if not disturbed much, will stabilize, and the drop in the SO2 level decreases.
▪ Bottling: Check the free-SO2 level prior to bottling and adjust as needed. Wines, even those that taste and smell fine, can go off quickly if bottled with insufficient SO2. The proper level will ensure that the wine will remain sound longer.
Adding SO2 (Potassium Metabisulfite):
▪ Potassium Metabisulfite (PMBS), a concentrated powder, is commonly used to add SO2 to juice, must, or wine. It can be added directly as a powder, or diluted with water in the quantities needed. PMBS powder contains 57.6% SO2 (Winy, an Enartis product (Winy) contains 56%).
Measuring SO2:
▪ PMBS, when added to water, juice, must, or wine, is measured in milligrams (mg) of SO2 per Liter (L) of the liquid. There are 1000 milligrams (mg) in a gram of SO2 and a 1000 ml in a liter of water. This makes it possible to express the SO2 addition as parts per million (ppm) — parts of SO2 per million parts of juice or wine. One ppm is equivalent to 1 milligram (mg) (.001 g) in 1L of water, juice, must, or wine. To convert gallons of juice, must, or wine to liters, multiply the volume by 3.79. There are about 25 gal (about 1hL) of must in a 32-gallon fermenting bin filled to the inner ring about 6 inches below the top. The size of the grapes influences juice yield ̶ larger grapes yield a little more juice and smaller grapes, a little less.
Ways to add SO2:
▪ 10 percent” stock solution ― An inexpensive and convenient way to add SO2 is to make a ‘10 percent’ stock solution. Add 100 g PMBS to a liter of water (~34 ounces), or 75 g PMBS to a 750 ml bottle filled to the standard height. This actually produces a 5.6 or 5.7% solution because the PMBS contains 56% or 57.6% SO2, depending on the product used. Make sure you check the label. Use the following amounts of the stock solution to add the desired ppm of SO2:
o 0.66 ml of a standard 10% (5.76%) PMBS solution adds 10 ppm SO2 to 1gal of must.
o Use a pipette with bulb for safety and to make more precise additions.
Use the table below to determine how much of the stock solution to add for the volume of juice/must or wine you have when using a 5.6% solution.
SO2 addition: 10% (5.6%) solution (Winy: Enartis)
| | 5gal| 10 gal | 15 gal | 30 gal | 60 gal |
|10 ppm |3.38 |6.76 |10.14 |20.28 |40.56 |
|15ppm |5.07 |10.14 |15.21 |30.42 |60.84 |
|20 ppm |6.76 |13.52 |20.58 |40.56 |81.12 |
|25 ppm |8.45 |16.9 |25.35 |50.76 |101.39 |
|30 ppm |10.41 |20.28 |30.42 |60.84 |121.67 |
|35 ppm |11.83 |23.66 |35.49 |70.98 |141.95 |
|50 ppm |16.9 |33.8 |50.7 |104.39 |202.79 |
Example: to add 30 ppm of SO2 to 15 gal of wine using a standard ‘10’ percent solution use ~30 ml of the stock solution.
o When using a PMBS product containing 57% SO2 to make a standard 10% solution add 3.32 ml to each 5 gal to raise the SO2 level to 10 ppm, add 6.64 ml for 20 ppm, and 9.96 ml for 30 ppm.
o Remember to stir the juice or wine after making an addition to disperse the SO2
▪ Direct powder (Potassium metabisulfite) addition:
o You’ll need a fairly accurate scale to weight the material. Using a measuring spoons is inaccurate.
o To add 10ppm to 5 gal of must or juice use .38 g PMBS (dissolved in water)
o To add 30 ppm to 5 gal. use 1.14 g PMBS
o To add 50ppm.PMBS to 5 gal of must or juice use .1.9 g PMBS
o For 15 gal: use 4g PMBS to add 35 ppm, 4.5g to add 40 ppm and 5.7 g to add 50 ppm
▪ Foil pouches containing powdered (effervescent) SO2:
o Offer a convenient but more expensive way to adjust SO2. One advantage is that you don’t need to stir the wine as with other means of adding SO2.
o Pouches or tablets containing 2-g or 5-g of PMBS are available. The effervescent mixture helps to distribute SO2 in the wine.
o When using the effervescent form, the 2 g-packet will provide 528ppm of SO2 per gallon of juice or must. Maybe a bit more than you need? For example, if you need to treat 25 gal of must/juice divide 528 (the amount of SO2/gal in each packet) by 25. Therefore, the packet will add 21 ppm of SO2 to 25 gal. Two 2 full packets will add 42 ppm. That’s fine for most reds or whites. For 10 gal of must a 2g packet will add 52.8ppm.
o One 2g-pkg of (Efferbarrique or Inodose granules or tablets) will raise the free SO2 level of a 59-gal barrel ~ 9 ppm, at least temporarily, a 30-gal container ~ 18 ppm and a 15-gal container 36 ppm.
o A 2 g-packet/tab will add about 21ppm to 25 gal (about 1hL) of must in a 32-gallon fermenting bin. (This is very helpful if you use 32-gal food-grade bins to ferment in). So, two-2g packets per 25 gal of must will provide roughly 42 ppm of SO2.
o If you divide the packages, remember that there is actually 5 grams of material (SO2 plus the effervescent agent) in a 2 g-packet ― so 2.5 g of the granules will provide 1g of SO2, enough to add 10.5 ppm to 25 gal.
o A 5 g-packet of Effergran or a 5 g Inodose Tablet will raise the free SO2 level in a 59-gal barrel to 23 ppm.
Factors affecting how much SO2 is needed:
▪ color of grape: white or red? More for whites.
▪ Condition of grapes: you’ll need more for moldy, bird-pecked, bee or yellow jacket damaged grapes.
▪ temperature of grapes when harvested, crushed, and/or pressed
▪ stage of winemaking
▪ pH of the must, juice, or wine
▪ sanitation practices
▪ handling (number of rackings, topping practices, how often you expose the wine to air, etc.
▪ number and types of additions: oak chips, cubes or an oak insert will introduce a lot of air, requiring additional SO2
▪ wines aged on the lees (sur lie) can get by with less SO2
▪ type of storage container used, oak barrels and plastic tanks and carboys are porous, glass and stainless tank are not
▪ how often you top your barrels.
▪ whether or not you use inert gas
▪ cellar temperature, etc.
17. Calculating how much SO2 to add:
▪ You can use the formula listed below to calculate how much PMBS to add, or the easy to use calculator: (make sure you enter 5.6% or 5.7 when using a stock “10%“ solution) or you can use:
Formula for PMBS addition
gal of wines x 3.785 x desired ppm = grams of PMBS to add
1000 x 0.56
▪ 3.785 converts gal to liters
▪ 0.56 is the fraction of SO2 in PMBS
▪ 1000 converts mg/L ppm to g/L
▪ A simplified version is: gal of wine x desired ppm x .0066 = g of PMBS
Getting Started: The winemaking process -
Sourcing grapes:
Grapes that are moldy, bird-damaged, over-ripe, under-ripe, or otherwise of poor quality, seldom produce good wines. Buy your grapes from growers or other sources in areas known for producing the variety you want, for example, Pinot noir from the Russian River appellation. Consider vineyard practices and look at the quality of the fruit. Check to see if the vines appear healthy and properly managed.
Cellar sanitation:
▪ Basic sanitation of all winemaking equipment, including fermenters and storage containers, presses, etc., is important. Clean all equipment used in winemaking to remove surface debris, dirt, staining, and residue, and then sanitize it. For more information regarding cleaning and sterilization, see the discussion on Sanitation section above.
Harvest:
▪ Ideally, grapes should be picked when they are ripe. Ripeness is usually expressed as percent sugar or °Brix (°B). California grapes are typically picked when the sugar levels are from about 23 to 26 (17.5 to 19 for sparkling) and 21.5 to 22 °B for some ‘crisp’ and austere whites). A refractometer is typically usually used to check grape sugar in the field. Grapes or clusters can be collected and tested later, using a hydrometer. The larger the sample, the more accurate the test. For greater accuracy, select whole clusters from different parts of the vineyard and different sides of the rows - say one cluster per every 10th vine. Select clusters that are shaded or receive ample sunlight. Place the grapes in a zip-lock bag, and crush to release the juice for testing. The bags with their contents can be frozen and added to the fermenting juice after you’ve harvested.
▪ It’s best to pick early in the morning when the grapes are cold. I’ve found it convenient to pick directly into 5-gal buckets. If you harvesting less than 200 pounds of fruit, you don’t need to transfer the grapes to a larger container for transit. If you’re picking more grapes, consider emptying the buckets or picking lugs into 32-gal food-grade ‘trash’ bins or macro-bin for transit. Keep the grapes cool by using dry ice or frozen water jugs in the transport bins. Cover the grapes the load during transit, particularly when the grapes will be exposed to direct sunlight. A tarp will also prevent lids from blowing off. I typically use trash bins to transport grapes, place one or two frozen water-filled jug among the grapes, especially if I have a long way to go or have to pick later in the day. Picking lugs and buckets can be easily emptied into the ‘stemmer’/crusher. Larger trash bins are best emptied by hand (wear Nitrile gloves to prevent bee or yellow-jacket stings. I’ve found that macrobins can be emptied more efficiently using a pitchfork.
▪ Harvest only the clusters that appear ripe and those that are free of mold. For whites ― a greenish-yellow or golden yellow color, depending on grape variety. Most red grapes are dark navy-blue. Avoid clusters with grapes that have a reddish cast. If in doubt, taste the grapes. Avoid picking clusters that are not uniformly dark blue. All of grapes should look like blueberries. Reddish grapes are not ripe and will skew flavors and acid levels. To determine the approximate yield of juice in gallons, divide the weight of the fruit by 15.
▪ Targeting a specific °B level is not the best way of ensure ripeness. Grapes can have a high °B but may not be fully ripe, and grapes can be ripe, even though their sugar level is seemingly low ― say 22.5. There are many variables that influence ripeness, so relying solely on °B can be a mistake. Things to consider:
o Color and taste are better indicators of ripeness.
o Berries should be soft and slightly dehydrated. The texture of the pulp softens when grapes ripen. When red grapes are fully ripe, the berries feel a little soft, and the skin becomes slightly slack, but not wrinkled like a raisin.
o Ripe fruit flavors - Under-ripe red grapes often have a green, herbaceous smell and taste reminiscent of bell peppers.
o Most of the stems as well as the seeds should be brown. The seeds should also be crunchy and have a nutty flavor. The color of grape seeds changes from green to brown as the berries ripen. Many experts feel 80 – 90% of the seeds should be brown before harvest.
o When grapes are fully ripe, the grape can be pulled away cleanly from the pedicel—small stem that attaches the grape to the cluster.
▪ Grapes are often left to hang after they are obviously ripe, in hopes of increasing fruitiness and pigment content. It can be challenging making a good wine from such grapes because the sugar levels are high, nutrient levels are often low, and the acid levels are typically low (high pH and low TA). Acid adjustments are important in such cases.
▪ Adjusting the acidity of juice from very ripe grapes typically involves adding Tartaric acid (see Adjusting Acid below).
▪ Adding water to high sugar juice will reduce sugar content and lower the resulting alcohol level. Too much alcohol can make a wine taste ‘hot’ (sense of burning in the mouth). Furthermore, the fermentation may stick unless you use an alcohol tolerant yeast. Stuck wines are often overtly sweet and subject to bacterial spoilage while you try to get the fermentation restarted. Something to keep in mind:
▪ Wines made from grapes that are ‘ripe,’ but have reasonably good acid levels are much less problematic and more stable. Grapes harvested much above 25B° should be diluted to keep the resulting alcohol level moderate (see Adjusting °Brix below).
▪ To estimate potential alcohol, multiply the °B by .57 (common conversion factor). For example: 26°B x .57 = 14.8%. If the °B level is 27, the resulting alcohol level will be 15.4 —very hot! If you dilute to 25, the alcohol will be 14.25%. If you dilute it to 24ºB, the alcohol will be 13.7% —quite acceptable. If you don’t dilute the must, select a yeast that can tolerate high alcohol to prevent sticking when fermenting high °B juice. Overly-ripe grapes are also low in nutrients essential for vigorous yeast development. To avoid problems, you’ll have to use ample yeast nutrients.
Temperature control:
▪ Warm grapes are prone to microbial spoilage, particularly during the cold soak phase (see Cold Soak below). Try to pick early in the morning so the grapes are relatively cool.
▪ Warm-grapes should be cooled to greater than
▪ High pH and low TA (pH >3.5 and TA 3.5 and TA >9g/L). This may be the result of high Malic acid, but this condition is fairly rare in California. It is usually the result of excessive Tartrate and excess Potassium ions. Such wines may resist adjustment and you may need to seek technical advice. High Malate is best remedied in the vineyard. High TA (greater than 10.5 is usually the result of too much Malic acid. You may need to do a ‘double salt’ treatment. Consult with ETS Wine Lab, Home Wine Lab, Gusmer, or Scott Labs, etc.
Treating common acid problems in juice:
Must/Juice Acidity Treatment Result
pH TA pH TA
Low acidity High (>3.5) Low (3.65 ↑ ↓
pH 3.65) High (>9g/L) Potassium Bicarbonate ↑ ↓
(Chill to ppt. KHTa)
High (9g/L) Potassium Bicarbonate ↓ ↓
(Chill to ppt. KHTa)
High (9g/L) Calcium Carbonate little change ↓
_______________________________________________________________________
▪ Maximum precipitation of KHTa during cold stabilization occurs at a pH of 3.65 or below. Above 3.65, KHTA precipitation lowers TA but raises pH. However below 3.65, pH decreases as well.
▪ High pH (>3.65) and High TA (>10g/L) must or wine, compounded by high Potassium or Malic acid can be a big problem. This may require using the ‘double-salt’ method of deacidification. Tough luck! You’ll need professional advice.
Acids and pKa values
Tartaric acid has two acid (-COOH) groups, each of which can lose its terminal hydrogen ion to the solution. Since Tartaric acid has two H+ ions or protons which may be released in solution, depending on pH. There are 2 dissociation equilibria known as (pKa’s). Stay with me here, I know it’s a bit over the top, but it’s an important concept. It’s probably more than you need to know, but helps to understand the process of acid adjustment.
The pKa of an acid is the pH value when 50% of the acid is disassociated or ionized in solution. Chemists use the concept of pKa to indicate an acid’s strength, and each acid’s pKa value(s) is a measure of the degree to which each acid ionizes. The higher the pKa, the less ionized the acid is at typical wine pH values. Tartaric acid has 2 pKa values, one occurs at about pH 3.0, and the other at about pH 4.25.
Equation 1. H2Ta (Tartaric acid) ↔ H+ + HTa
(HTa- or (Bitartrate ions predominates at pH ~3.0 to ~3.65: (pKa = 3.04)
Equation 2: H+ HTa- ↔ 2H+ + Ta2-
(Ta-2 or Tartrate ions predominate at pH 4.25 (pKa = 4.25)
The figure below shows that Tartaric acid’s first pKa occurs where the red and blue lines intersect ―around pH 3. The second pKa, where the red and yellow lines intersect, occurs a little above pH 4. At the first pKa the ratio of un-ionized Tartaric acid (H2Ta) and Bitartrate (HTa-) is 50:50. At the second pKa the ration of HTa- (Bitartrate) to Ta2- (Tartrate) is 50:50. We see that at the lowest levels of pH, Tartaric acid exists in solution primarily in the un-ionized state, but at pH levels between the two pKa values, the singly-ionized state (Bitartrate) predominates. At pH levels much above the higher pKa value most of the acid is present in the doubly-ionized tartrate state. At typical wine pH levels (about 3.4) most of the Tartaric acid is in the singly-ionized state (Bitrate form), but there is some un-ionized and doubly-ionized acid present. The level of HTa- is equal to the un-dissociated Tartaric acid and H2Ta at pH 3.04 and increases to its highest point at pH 3.65. The level of Tartrate Ta-2 and HTa- is equal at a pH of 4.25.
[pic]
Tartaric Acid. The blue line represents the fraction of the acid that is un-ionized, the red line represents the singly-ionized acid, and the yellow line represents the doubly-ionized acid. Note in the chart for tartaric acid (Figure 2) that three curves are required to define the three possible ionization states for the tartaric acid. In this chart the lower pKa value is indicated by the point at which the blue and red lines cross, and the higher pKa value is indicated by the point at which the red and yellow lines cross. We see once again that at the lowest levels of pH, tartaric acid exists in solution in the un-ionized state, but at pH levels between the two pKa values, the singly-ionized state is the most populated, and then at pH levels much above the higher pKa value most of the acid is present in the doubly-ionized state. At typical wine pH levels (about 3.4) we should expect most of the tartaric acid to be in the singly-ionized state, but there will be some un-ionized and doubly-ionized states present, too. Dale Ims How wine acids’ pKa values control pH and why pH will go only so low
So, what’s the big deal? When tartaric acid ionizes, the Bitartrate that forms, binds with K+ (potassium ions) and precipitates as an insoluble salt in the presence of alcohol. This removes acid from the wine. The higher the concentration of Bitartrate, the greater the effect. The peak concentration of Bitartrate is at pH 3.65, and it drops rapidly as pH increases.
How pH influences acidity:
▪ When Bitartrate precipitates, TA is always lowered. How pH changes, depends on the pH value at which the KHTa precipitation occurs.
▪ The higher the concentration of Bitartrate ions, the greater the reaction, and the peak concentration of Bitartrate is at pH 3.65.
▪ So, when pH is ≤ 3.65, Potassium Bitartrate readily precipitates out of solution during fermentation and later during cold stabilization, as well as in finished wine, effectively lowering both TA and pH.
▪ This works because Potassium ions (K+) in the juice or wine, combine with Bitartrate ions (HTa-), forming Potassium Bitartrate (KHTa), an insoluble salt. This eliminates excess Tartaric acid and reduce TA. However, the H+ ions are released during the reaction, lower the pH. The reduction in KHTa concentration shifts equilibrium in the reaction below to the right to maintain equilibrium.
H2Ta (tartaric acid) → HTa- (Bitartrate ion) + H+ + K+ ↔ KHTa↓ (Potassium Bitartrate) + H+
▪ When pH is above 3.65, Potassium Bitartrate precipitation lowers TA↓ as you would expect but raises pH↑. Seems weird, but here’s how it works. The precipitation of Bitartrate eliminates some Tartaric acid, which decreases TA. At high pH, most of the existing ions in solution exist as Tartrate ions (Ta-), so precipitation of KHTa shifts the ionization reaction left to form more HTa-. The problem is that pH goes up because the reaction’s equilibrium shifts left from the Tartrate side of the equation (Ta2- + 2H+) to replenish Bitartrate lost to precipitation, resulting in the neutralization of one of the 2 H+:
HTa--↓ + H+ ← Ta2- + 2H+ (a net loss of 1H+)
Raising acidity:
▪ Grape juice should be adjusted if the acidity of the wine when finished is likely to be flat and uninteresting or just imbalanced. Relatively large acid adjustment should be made early in the wine-making process rather than later. Minor adjustments can be made after fermentation and MLF.
▪ Use Tartaric acid to lower pH and raise TA of juice or wine. This occurs because you’re adding a relatively strong acid that will increase the level of Hydrogen ions (H+) in the solution. Other acids such as citric or malic are generally not recommended for adjusting wine.
▪ As a rule of thumb: 1 g/L or 3.8g/gal of tartaric acid per gal. lowers pH by roughly 0.1 unit, but occasionally as much as 0.2 units. (Clark Smith, Vinovation). So, add the acid gradually in 3 to 4 additions, and measure the pH after each partial addition.
▪ When adjusting TA for red grape, consider that 60 to 70% of the must is actually juice when calculating how much Tartaric acid to add.
▪ The addition of a given amount of acid to a wine may not reduce the pH as expected due to the wine’s buffering capacity to maintain a stable pH.
▪ It’s seldom a 'one-to-one' reaction.
▪ When added to juice or wine, Tartaric acid, dissociates (splits into charged particles (ions), in a reversible manner, but primarily to Bitartrate ions (HTa-)
▪ The amount of Tartaric acid and its ions are in equilibrium, dependent on pH. The reaction is as follows: H2Ta ↔ HTa- + H+ ↔ Ta2- + 2H+ (↔ indicates equilibrium).
▪ When treating wines with high pH and low TA, simply you add Tartaric acid and the TA goes up, and pH comes down as needed. Now, if you add more tartaric acid the TA may be above what you want, and the pH is still too high. The trick is to add enough acid to get the pH down to 3.65 or below. At the point the precipitation of Potassium Bitartrate (KHTa) will lower TA a bit, and in the process release H+ into the solution, lowering pH as well. If you don’t add enough, pH will go up as well as TA—not what you had in mind. Once you reach a pH of 3.65 or less, TA will begin to drop to an acceptable level as the KHTa precipitates out of solution. The reason is that the availability of HTa- ions is much less, but increases to it’s the maximum availability once pH is 3.65 or lower.
▪ Make adjustments incrementally to avoid excess acidification. After each addition, mix thoroughly, and allow it to stand for an hour or two, and then measure and taste to see the results. Determine if more acid is likely to improve or diminish taste.
▪ Bench trials: You can also do bench trials to determine how much Tartaric to add to your juice of wine by preparing a 10% solution (10g Tartaric acid in 100 ml of distilled water. Set up 3 to 4 glasses, each containing 100ml of juice. Reserve one glass for a control. Mark the glass in numerical order and ’C’ for control. Depending on acidity, add 1, 2, and 3 ml, if needed, of the 10% Tartaric acid solution to the glasses, and then taste and measure the TA and or pH change. The amount of the 10% solution used is equivalent to the grams per liter of acid needed to make the best adjustment. This is because one ml of the solution equals one gram of acid. By using a 10% solution, testing is a quick way to determine how much acid is necessary to balance your juice.
▪ Bear in mind, that you should rely on your palate when making adjustments. If a wine tastes fine after making a partial addition, consider if adding more is likely to improve the results, if not you’re done.
Key points: the following is a bit complex, but may be of some use in understanding how grape juice, must or wine responds to acid adjustment.
▪ Potassium Bitartrate, an insoluble salt, forms during fermentation and cold stabilization. Bitartrate ions in the juice or wine bind with Potassium ions (K+) and precipitate out of solution, eliminating some Tartaric acid. The higher the concentration of Bitartrate ions, the greater the reaction, and the peak concentration of Bitartrate is at pH 3.65.
▪ When pH is less than 3.65, precipitation lowers TA as you would expect, but reduces pH because the reaction shifts to the right.(red arrow). Note that H+ is released into solution.
H2Ta → HTa- + H+ + K+ ↔ KHTa↓ + H+
▪ When pH is greater than 3.65, TA goes down but pH goes up. At high pH, most of the existing ions in solution exist as Tartrate (Ta-), so precipitation of KHTa shifts the ionization reaction left to form more HTa-. This decreases pH by neutralizing 1H+.
HTa--↓ + H+ ← Ta2- + 2H+
Lowering acidity:
▪ If the pH of your juice is unusually low or the TA is unusually high, you’ll need to adjust acidity. Bear in mind that acidity drops during the wine-making process – pH goes up and TA come down, however it may not be enough for the finished wine to taste. balanced
▪ Adjustments for high acidity wines (low pH and high TA (up to pH 10.5 g/L), is straight forward. Simply add Potassium Bicarbonate. It is the preferred material for home winemakers (KHCO3). Potassium Carbonate (K2CO3) can also be used has a short shelf-life and should be used quickly.
▪ Either agent will lower TA and raise pH.
▪ Make adjustments as needed, preferably before fermentation.
▪ Small acid corrections (around 1 g/L) can be done after alcoholic or malolactic fermentation. It can, however, result in tartrate instability if cold stabilization has already occurred.
▪ If TA is above 10.5, determine if the cause is excess Malate or Tartrate. Consult a wine lab, e.g., ETS Wine Lab, Home Wine Lab, Gusmer, or Scott Labs, etc., for advice. The treatment is beyond the scope of this manual.
▪ In general, the pH of red grapes should be adjusted close to 3.5 so that the finished wine will not be too high (above 3.8).
▪ pH will increase when you add Potassium Bicarbonate or Potassium Carbonate, but the change is not linear. pH change is closer to .2 units for each 1g/L drop of TA in high TA and low pH wines.
▪ So, make the addition gradually, say one third or one half the calculated amounts and to see how the wine responds. It’s also prudent to experiment using 1 gallon of the wine rather than the whole lot. If you screw it up you can blend it back into the rest of the wine or juice and start over.
▪ Dosage rate to lower TA by about 1g/L: 3.4 g/gal of Potassium Bitratrate, or Potassium Carbonate at the rate of of 3.55g/gal when pH is >3.45 but 1.75g/gal when pH is < 3.45,). Reference: Enartis (Vinquiry)
▪ Add directly to the juice or wine or you can dilute with a little water and stir to distribute it throughout the container. Wait for about 15 to 20 minutes to measure pH or TA.
▪ Using Potassium Bicarbonate to adjust high pH and high TA (above 10g/L) juice/must/ is generally not an effective to achieve balance in reducing the acidity adequately without raising the pH excessively. You may need to consult a wine laboratory.
▪ Calcium Carbonate can be used to treat high pH and high TA juice or wine, but is mainly recommended for making large (more than 3 g/L TA adjustment. This reaction commonly produces Calcium Tartrate (CaTa), an insoluble salt. The reaction does not require chilling, but may take up to 6 weeks or longer for the CaTa to settle precipitate.
▪ Its main advantage is that it delivers the maximum acid reduction with a minimum increase in pH
▪ It should be added only at the juice/must stage.
▪ The drawback is that It can impart a slight chalky taste when large (>3g/L) additions are made.
▪ Use Calcium Carbonate at the rate of .67g/L to reduce TA by 1 g/L.
▪ You can find online calculators to help determine additions: , , ),
Important concepts for lowering acidity: Potassium Bicarbonate is the preferred chemical agent to lower acidity of juice, must, or wines with (low pH and high TA). It works by removing tartaric acid which neutralizes 2H+ ions in juice or wine, thereby increasing pH.
▪ Here’s how it works: The carbonate anion (CO32–) reacts with acid (H+) in the juice/wine, forming bicarbonate ions (HCO3–), which react to form carbonic acid (H2CO3), which breaks down to carbon dioxide gas and water (H2O). The formation of water results in the neutralization of 2 H+ ions from the solution.
▪ Because the potassium (K+) ions combine with Bitartrate ions, forming and insoluble salt. Consequently, TA decreases, but how pH changes will depend on the pH of the solution. Above 3.65 the pH increases, while below pH3.65 is decreases.
▪ The schematic chemical reaction for adding Potassium Bicarbonate to juice or wine is:
o KHCO3 + H2Ta (in juice or wine) → KHTa(↓) + H2CO3 → CO3-2 H+ → HCO3– + H+ → H2CO3 → CO2 (bubbles) + H2O.
o When the pH of the solution is less than 3.65, pH decreases because H+ is released into solution: H2Ta ↔ HTa- + H+ + K → KHTa↓ + H+
▪ The reaction when Calcium carbonate is used: CaCO3 + H2TA → CaTa(↓) + CO3-2- + H+ → HCO3– + H+ → H2CO3 → CO2(↑) + H2O (2 H+ are neutralized. Obviously, TA goes down but pH goes up.
Natural pH changes during winemaking:
▪ Potassium is a critical factor in the precipitation of bitartrate ions and reduction of acidity.
▪ Bitartrate ions in the presence of alcohol and potassium ions combine to form KHTa Potassium Bitartrate, effectively lowering acidity.
▪ The maximum bitratrate concentration in juice and wine occurs is at roughly pH 3.6.
▪ The greater the number of free-Potassium ions in solution, the greater the reduction in acidity during winemaking.
▪ Acidity change in reds is greater than that of whites, because more potassium ions (K+) are extracted by to prolonged skin contact during cold soaking, and fermentation on the skins.
▪ Juice/must high in Potassium ions also resists pH adjustment because of increased buffering capacity.
▪ Diluting high B° grape must with water will reduces TA, but not pH due to the buffering capacity of the juice. Depending on the starting of TA, this may be beneficial.
▪ pH may go up as much as .2 pH units during cold-soaking due to release of K+ ions.
▪ Potassium K+ ions in juice/must combine with Bitartrate ions. (HTa-) to form Potassium Bitartrate (KHTa), an insoluble salt. What happens with pH really depends on the pH of the juice/must:
o Below pH 3.6, Potassium Bitartrate readily precipitates out during fermentation and later during cold stabilization, as well as in finished wine, effectively lowering both TA↓ and pH↓. This works because potassium ions (K+) in the juice, must or wine, combine with Bitartrate ions (HTa-), forming Potassium Bitartrate: KHTa). This, of course, eliminates some of original Tartaric acid and lower TA↓. However, H+ ions released during the reaction, lower pH↓. The reason for this is that the loss of Bitartrate ions shifts equilibrium in the reaction below to the right, replenishing Bitartrate ions lost to precipitation, producing more H+:
H2Ta ↔ HTa- + H+ + K → KHTa↓ + H+
o Above pH 3.6, Potassium Bitartrate precipitation lowers TA↓ but raises pH↑. Seems weird, but how it works…The precipitation of Bitratrate (KHTa) eliminates some tartaric acid, decreasing TA. pH, however, goes up because the reaction’s equilibrium shifts left from the Tartrate side of the equation to replenish Bitartrate lost to precipitation, resulting in the neutralization of H+: This in turn, raises pH↑.
HTa--↓ + H+ ← Ta2- + 2H+ (a net loss of 1H+ so pH has to go up.)
▪ Primary fermentation and cold stabilization cause pH to increase by 0.1 to 0.2 pH units, and the TA to drop by as much as 1g/L as tartrates (from the dissociation of tartaric acid) binds with K+ ions, forming Potassium Bitartrate.
▪ Cold stabilization maximizes the precipitation of Potassium Bitartrate, lowering TA. The colder the wine the more KHTA precipitation.
▪ MLF also causes acidity to change: pH↑ by about 0.2 units and TA↓ by 1 to 2 g/L or more.
Problematic grapes:
▪ During a cool, long season, pHs may be high ̶ close to 4 and above, the culprit may be is high malic (under-ripeness). Extended hangtime In California, however, may results in high-potassium juice and wines that resist pH adjustment with tartaric.
high potassium (K+) (over-ripeness). Treatments differ entirely. In 2011, it wasn’t unheard of to get both conditions in the same must.
▪ Read more at:
▪ Copyright © Wines & Vines High TA musts in California typically have high levels of tartaric acid and Potassium. The Potassium is often the result of high ripeness or stressful growing conditions.
▪ If an acid addition doesn’t help high pH and high TA wines, the problem might be excessive Potassium and/or high Malic acid (cold years). Such wines are difficult to fix. This is fairly rare, but if it happens you should get technical advice from a wine lab.
▪ After making an acid adjustment, and TA is moderately high and going up, but the pH is still high, it’s likely that you haven’t added enough Tartaric acid yet. You need to get the pH below 3.65, at which point the precipitation of Potassium Bitartrate will ultimately lower both TA and pH, solving your problem.
▪ For example, your juice has a TA of 10 g/L and pH of 3.9. You’ll need to add Tartaric acid to lower pH to about 3.6, the peak of the bitartrate curve. You might need to add 2 grams per liter, and end up with a pH of 3.6 and a TA of 12 g/L. Don’t try half measures, as it will appear that it didn’t work when the pH comes right back up. Then chill the bottle overnight, spin/settle/filter a few mls clear, and test the TA and pH. Typically, you would end up with pH 3.6 and maybe a TA of 8.5 g/L and lots of KHTa. Not bad! This works because you have lots of potassium and you are at the peak of the bitartrate curve.
▪ Problems can also result when there is too much malic acid (a low tartrate: malate ratio), which is frequently linked to over-cropping, dense canopies. You’ll need to test for this condition) and you may need to resort to ‘double-salt’ deacidification. A simple, but time-consuming test involves adding 5 g Tartaric acid to 50 mls of warm water to acidify a 50 ml sample of the must to pH 3.6. Freeze the sample vial overnight, then then allow it to thaw. A deposit of white crystals at the bottom of the vial indicates excess Malic acid in the sample. Test some of the clear juice for TA. If the problem is a high potassium level, the TA will have dropped to about 8.5 and the pH will remain relatively unchanged. If this is the case, lower the pH of treat the bulk of the must with Tartaric acid to 3.6. At that point the TA will drop due to precipitation of Bitartrate.
▪ If the problem isn’t excessive Potassium, then it’s probably too much Malic acid and you’ll have to do the double salt deacidification. The double salt CaCO3 deacidification involves both Tartaric acid and Malic acid.
▪ You may need to add Calcium carbonate (CaCO3) mixed with calcium tartrate and calcium malate to correct the problem. It will cause calcium maleate and calcium tartrate to precipitate at high pH. This is usually done by adding an excess of CaCO3 to 20 to 30% of the wine and later recombining the 2 lots. This will lower TA and pH. The wine can then be acidified with tartaric acid if necessary. Allow the salts to precipitate and settle out and then rack off the crystals and lees. This is a difficult process and you need expert advice.
▪ If malic acid is high, some strains of Saccharomyces cerevisiae (e.g., Lalvin 71B or Lalvin AC) can metabolize 20 – 40% of the malic acid present in a must, producing alcohol instead of lactic acid.
▪ For high pH and high TA juice: Adding acid can solve a high pH, high TA must—really? It seems counter intuitive, but yes, it actually works. If you add 2 g/l of Tartaric acid to a grape must with a high pH of ― say 3.9 and a high TA — say 9.0 g/L, the pH may drop to about 3.55 (changes are not always linear). But as you would expect, TA will go up to 11, this is not good! but because the pH is now below 3.6, tartrate precipitation will act to lower the TA to about 7 — Hallelujah! This wine, following cold stabilization, could wind up with up with a pH of 3.4 and a TA of 6.3
Stemming/crushing and processing red and white grapes
▪ Once your grapes have been harvested, keep them as cold as practical until you’re ready to crush and destem them. It’s best to do so without delay.
▪ Warm grapes are prone to microbial spoilage, particularly during the cold soak period, if you choose to do so (see Cold Soak below).
▪ Chill grapes using dry-ice, dry-ice pellets, frozen water-filled jugs, or refrigeration.
▪ Dry-ice is good as it also releases CO2, displacing air and preventing oxidation. You can also blanket the must with argon, and then cover the fermenter.
▪ Avoid direct exposure of the grapes, or must to sunlight.
▪ Make sure that all your equipment has been cleaned and sanitized, as well as practical.
▪ Red grapes can be destemmed without crushing using a de-stemmer rather than a ‘stemmer’-crusher. In this manner, whole berries are collected and allowed to ferment. The fermentation occurs primarily within the grape skin (carbonic maceration), resulting in a fruiter and less tannic wine.
▪ Red grapes can be crushed directly into open-top stainless-steel fermenters, plastic food-grade containers, or macro-bins, depending on the quantity of grapes. Plastic food-grade bins are convenient because they can be easily cleaned, stored, and moved around when attached to the available wheel dollies. Punch-downs are easier and the containers can easily be covered with to exclude fruit flies. The solid plastic lids don’t provide a good seal against fruit flies, old beach towels work well to keep exclude fruit-flies and allow CO2 and water vapor to escape.
▪ For whites, it’s most convenient to crush/destem the grapes into 32-gal white plastic food-grade ‘trash’ bins. The available wheel dollies allow them to be ‘wheeled’ under the stemmer/crusher and away from it once they’re filled. Another consideration is that they can be moved around the work area as needed or to free up space. Various winemaking additives such as SO2, enzymes, fermentation tannins, etc., can easily be added and mixed during skin contact.
▪ Four to five 32-gal plastic bins will handle about 1000#’s of fruit.
▪ At this point, add 30 to 40ppm of SO2 and make sure it is well dispersed throughout the must.
▪ In most cases, you’ll want to add SO2 to the grape must in the holding/fermenting container(s) immediately after crushing. (see To sulfite on not to sulfite, below).
▪ Keep the must or whole berries chilled during skin contact (whites and rosés), and when cold-soaking reds.
▪ Skin contact (see Skin Contact below) enhances varietal character, but too much may increase astringency and darken color.
SO2 addition: Pre-fermentation addition both red and white grapes:
▪ For home winemakers, this can be very confusing. The amount of SO2 to add should be based on the total volume (gal) of must after stemming and crushing, even though grape must contains skins and seeds which will be removed at pressing.
▪ About 30 to 40 ppm of SO2 added immediately after crushing is adequate to minimize microbial problems for both reds and whites. Higher SO2 levels are recommended for warm grapes and those with bird damage and rot.
▪ Add the SO2 and vigorously stir to thoroughly disperse it throughout the juice.
▪ Levels much above 50 ppm at fermentation are likely to inhibit malolactic fermentation (MLF), see MLF below).
▪ If the intent is to make a fresh, fruity, and crisp white, you can add up to 75 ppm SO2 to effectively inhibit MLF.
▪ Chilling your grapes will reduce the amount of SO2 needed.
▪ For each 5 gal of must:
o ~10 ml of a standard 10% (5.7%) PMBS solution will add 30 ppm SO2
o 11.6 ml adds 35 ppm
o 13.4 ml adds 40 ppm
o 16.5 ml adds 50 ppm
o 25.0 ml adds 75 ppm
▪ If you use powdered PMBS you will need to add 0.33 grams to provide 50ppm of SO2 for each gallon or 1.65g/5gal.
▪ Mix well to disperse, particularly before adding enzymes (optional).
▪ Some professional winemakers use as little as 20 ppm of SO2 before fermentation. Home winemakers, however, would do well to use a higher rate because they generally lack the experience, technical know-how, specialized equipment, temperature control, and access to sophisticated testing equipment. Commercial winemakers also have greater control over grape quality and harvest temperature.
▪ Note: not all of the SO2 you add will remain in the finished wine, some will bind up with solids that settle out. In reds, some of the SO2 is lost to the atmosphere during ‘open-top’ fermentation and later during racking.
To sulfite or not to sulfite? Two options for fermenting grapes use to make white wines and rosés:
Option 1: Add the SO2 (say 35 to 40 ppm) immediately after crushing to prevent browning and oxidation. The benefit is that there will be less browning and acetaldehyde formation in the wine. The drawback is that more SO2 (50 to 75ppm) will be needed after fermentation because virtually all of it will be bound up or lost to the atmosphere during fermentation.
Option 2: Withhold the SO2 until after fermentation. This will allow the juice to turn brown (enzymatic browning). Most of the browning, however, will drop out after fermentation. The upside is that there will be less total SO2 at bottling. The downside may be a slightly higher VA (volatile acidity—vinegary or like nail-polish remover. Harvesting and crushing the grapes when they are still cool, and attention to sanitation will help minimize the formation of VA. There is also some risk of bacterial spoilage if grape quality is poor, temperature control is lacking, you have no means of blanketing the must/juice with argon or CO2, or the fermentation is sluggish or sticks. It’s best to use a commercial yeast and add sufficient yeast-nutrient to promote a healthy fermentation. This method is most successful when the condition of the fruit is good and temperature can be maintained below 60°F, and the grapes are not overripe. Wines made in this manner may lose some fruitiness but may gain in complexity. Your choice…
Skin contact: when making white or rosé wines:
▪ After crushing, add SO2 and mix thoroughly to disperse it, particularly before adding enzymes. Consider using a macerating enzyme like Enartis Aroma MP at this point during skin contact (see se Enzymes below.
▪ Crushed grapes that have been chilled to at least 60°F can be pressed immediately or allowed to sit for 2 to 8hrs before pressing with or without an enzyme. If you want to make a light colored, French-style rosé, press shortly after crush. Red grapes can be presses within minutes of crushing if you want just a hint of color, pale peach or salmon, press the cluster whole. This, however, is more work, and the yield is less. It’s best to use a bladder press and use only the free run and light press wine. Hard pressed wines should be kept separate and you may want to use a special carbon black product such as Enoblack-Perlage (Enarttis) to lightly strip the darker color.
▪ Skin contact enhances varietal character, but too long will increase astringency and imparts more color.
▪ It’s important to keep the grapes cold, preferably 50°F or less during skin contact. Use dry ice, frozen water-filled jugs or refrigeration.
▪ Blanket the container with inert gas, such as Argon. Dry ice, which releases CO2, can provide additional protection.
▪ If you’re unable to chill the grapes sufficiently to protect them from spoilage bacteria, e.g., Lactobacillus, Pediococcus, etc.), you can use Lysozyme or Enartis Stab Micro M (expensive). Both can be uses in high pH wines which are inherently unstable, to prevent spoilage or prevent MLF later. If you add Lysozyme you will need to fine the resulting wine with Bentonite for to prevent a protein haze from forming.
Enzymes for making white or rosé wines (optional):
▪ Enzymes are commonly added during skin contact to release aromatic compounds, increase yield,
▪ Macerating enzymes, for example, ZYM AROM MP (best for rosés), ZYM CHARACTÉR (Enartis). Cuvee Blanc or Color Pro. (Scott) also work well. Macerating enzymes increase aromatic extraction, press yield, clarification, and protein stability. Recommended contact time is 4 to 6 hour, although 2 to 3 works reasonably well.
▪ For some grapes, like chardonnay, settling occurs rapidly and without the need for enzymes or other additions.
▪ Clarifying enzymes, for example ZYM RS(P) (Enartis) provide good clarification particularly for whites that are hard to clarify like Sauvignon, Blanc, Pinot Gris, Gewurztraminer. It should be added at the start of settling. Four to six hours of contact is generally adequate. Lallzyme C-Max (Scott) is also very good for clarification for most whites.
Pressing white and red grapes for rosé:
▪ Press after the desired period of skin contact (0 to 8hrs) to remove skins and seeds.
▪ The juice that flows out of the press before any pressure has been applied, and the juice that flows under relatively low pressure is called ‘free-run’. The juice that flows freely as pressure is applied can be considered free run as well. Some people prefer to keep the juice produced under high pressure, separate from the free-run juice because it can be more astringent and darker in color. The color may actually turn dark brown toward the end of pressing.
▪ Bladder presses apply less pressure and there is little difference between the wine that flows early-on and the wine that flows later. It’s not until you get down to a narrow stream and the ‘cake’ (skins and seeds) is relatively hard-packed.
▪ One option for ‘hard press’ juice is to use a fining-agent like Clargel (Enartis) or Colle Perle (Scott) to remove harshness and astringency due to seed tannins and oxidative browning.
▪ Take your time when pressing and avoid extreme pressure. Fill your basket press about 80% full.
▪ Bladder presses should be filled to capacity, but don’t pack the grapes, even if there is only a small amount left. These can add later after an initial pressing creates the needed space. If you don’t have enough grapes to fill a bladder press completely, partially inflate the bladder to reduce space around the bladder until the grapes just fill the void. It’s not a good idea to run the bladder press unless the basket is filled. The bladder is more likely to fail if does not inflate uniformly.
▪ Bladder pressing is gentler than basket pressing—it generally results in wines that are less harsh and bitter.
▪ Bladder presses which normally use water pressure can be easily converted to using compressed air to do the work. You’ll need a few pipe fittings, and a small, portable air compressor with an accurate pressure regulator to prevent damaging the bladder and screen. Using too much pressure can damage the metal basket, lose the wine or juice or cause serious personal injury.
▪ You don’t need much air pressure to press the grapes — 8 to 10 psi (pounds per square inch) will do the job. It just takes a little longer, but the results are better, and the operation safer. Monitor the compressor’s pressure gauge to make sure the pressure is within the safe range. To be on the safe side, do not exceed 2 bars ~29 psi. Read the instruction for your bladder press and operate the press within their safety margin.
▪ Using a basket press can be tedious and labor intensive. Although expensive, bladder presses are well worth the cost in terms of convenience and reduced labor and time involved. If you are serious about making wine, put one on your wish list, and then figure out how to pay for it. I recommend going in with several other winemakers to purchase one.
Settling (clarifying) the pressed juice from grapes used to make white and rosé wines:
▪ After pressing, it’s convenient to place the freshly pressed juice in clear, food-grade plastic carboys for up to 12 hours or a little longer if needed to allow the solids (gross lees) to settle out.
▪ Initially the juice is very cloudy (looks like pea soup) because it contains a lot of extraneous solids.
▪ This is a good time to add the enzyme RS(P) to facilitate settling. Other enzymes may do just as well for most grape varieties
▪ Store the juice during settling in a cool room. You can also immerse carboys in cold water or cover each with a wet tee-shirt that is moistened periodically. The loss of water due to evaporation naturally cools the containers.
▪ Once most of the solids have settled to the bottom and the juice is reasonably clear, typically 8 to 12 hours, or longer in some cases, you’ll need to transfer the juice to a suitable fermenter, leaving the lees behind.
▪ Unless removed, the gross lees will contribute harshness, astringency, and herbaceous notes, and the resulting wine may develop reduced (stinky or sulfury) notes.
Racking (siphoning) settled juice off grape solids:
▪ Rack the clarified juice into sanitized fermenters, e.g., carboys, beer kegs, or larger stainless or plastic tanks approved for fermentation.
▪ Use a siphon hose with a baffle on the end, to draw juice from just above the solids (heavy lees), otherwise some of the sediment will be pulled up the tube. Tilt the bottle toward you, as the level drops to raise the level of juice above the siphon tip to increase yield and minimize uptake of solids. A little solid material is not a problem. Discard the remaining sediment.
▪ Allow about 10 percent head-space in the fermenter(s) to accommodate the foam generated by the yeast during an active fermentation. Some yeasts produce a lot, while others, very little. If you over-fill your fermenter the foam may blow off the air lock or escape through it, creating a ‘bloody’ mess. I’ve had to clean yeast residue off the floor, ceiling, and walls because I failed to leave adequate head-space.
▪ The juice from Sauvignon blanc, in particular, does not settle well, unless you use the right enzyme, and after racking the clear portion, there is still a lot of juice mixed in with sediment. Rather than discarding this turbid juice, reserve it and ferment it separately. In my experience, the result has generally been good or at least acceptable. You will want to rack it off the lees as soon as the solids begin to settle, usually toward the end of fermentation. Because the heavy lees contain some elemental sulfur from the surface of the grapes, you may get the formation of H2S (rotten egg smell). If the wine is stinky, rack the wine to allow the compound to escape. If the odor persists, you can use a product like Revelarom (Enartis) or Reduless (Scott), a yeast-based material infused with copper. This should correct the problem. Depending on aroma and taste, this wine can be bottled separately, blended into the rest of the wine, used to make a white blend, or discarded, if need be. I’ve found that certain fining agents, such as Claril SP (Enartis), Clargel (Enartis) or Colle Perle (Scott) can significantly improve the wine.
Fermentation tannins when making white or rosés wines (optional):
▪ Fermenting tannins are used to reduce oxidation, enhance aromatics, improve mouth-feel, remove unstable proteins, and bind with anthocyanins (pigments) to create more stable color.
▪ If you’re using an enzyme, allow 6 to 8 hours for it to work before adding fermentation tannins. Tannins, however can be added to must treated with ZYM RS(P) within 30 min.
▪ Some choices for whites:
o (Enartis: Tan Blanc (whites and rosés), Tan Clar (good for Sauvignon blanc, Pinot gris and Gewürztraminer), Tan Arom (aroma enhancement), Tan Elegance (also enhances flora notes and improves mouth feel).
o Scott: FT Blanc Soft or FT Blanc (also good for moldy or high protein grapes, e.g., Sauvignon blanc, Pinot gris, and Gewürztraminer).
Preemptive fining: highly recommended when making white and rosé wines
▪ The use of fermentation tannins early on, can greatly reduce the level of unstable proteins in white and rosé wines.
▪ Unstable proteins can be problem in whites and rosés, particularly those that are not aged in oak. White varieties contain variable amounts of proteins that can in settle out with time or exposure to warm temperatures, even under good cellar conditions, and diminish appearance. You can treat (fine) during settling or fermentation (preemptively) or after fermentation.
▪ Preemptive fining Is done after the juice had had time to settle and has been racked off the heavy lees, usually just after active fermentation starts, or even mid-way through the fermentation.
▪ The objective is to remove proteins that can precipitate after bottling when wine is warmed. Bentonite, which has been traditionally used for this purpose, can be added during fermentation or later. It is thought however, that early fining results in significantly less stripping of aroma and flavor, and reduces the amount needed later. Protein levels are largely dependent on the grape variety, vineyard location and practices, the vintage, and how the grapes are handled during pressing and crushing. The longer the juice is exposed to the skins and the more the skins are manipulated, the greater the protein content of the wine.
▪ Various formulations containing bentonite, such as Claril SP (Enartis) or Bentolact (Scott) remove unstable proteins, settle solids, reduce bitterness, harshness, and browning, improve aging potential and aromas, and minimize oxidation. It can greatly improve the quality of ‘hard-press’ juice. In addition, it is reported to have a minimal stripping affect.
▪ These formulations are generally added at the onset or midway through the fermentation, to allow the tannins and enzymes to work. Bentonite will denature both of them.
There are a number of products that can remove the unstable proteins, improve clarity. Some will reduce astringency, bitterness, oxidation, and improve aroma.
▪ Bentonite—is very commonly used and widely recommended to remove proteins (heat stabilization) that can precipitate in the bottle during storage, particularly when the wine is warmed. Bentonite (Calcium- or Sodium-based). Silica gel a counter-fining agent, can be used to increase the rate of settling the finer particles that are slow to settle. Rate: 20 to 100 ml/hL
▪ Pluxcompact (Enartis)—a calcium-based form of bentonite produces more compact lees., Rate: 20 to 120 g/hL in 20 times its weight in cold water
▪ Pluxcompact N (Enartis) —a sodium-based bentonite. Rate: 20 to 120 g/hL in 20 times its weight in cold water
▪ Bentolact S (Scott) Bentonite plus Potassium Caseinate—reduces astringency and bitterness, binds with excess phenolic compounds and mitigates oxidization. Rate: 20-100 g/hL
▪ Claril SP (Enartis)—includes Bentonite, PVPP, casein, and silica gel. It is also used to remove unstable protein, and oxidized polyphenols, increase clarity, and reduces bitterness, and. Rate: 50 to 150 g/hL,
Red grapes: cold-soaking (maceration) prior to fermentation
▪ After de-stemming and crushing red grapes add 30 to 50 ppm of SO2 to the must to prevent spoilage particularly during cold-soaking.
▪ Unless you are making a rosé, red grapes are fermented on the skins and seeds.
▪ Cold-soaking, as the name would imply, is the practice of allowing the juice, skins and seeds to after crushing to soak after chilling for a day or two or even longer depending on the winemaker’s objective. It’s critical to keep the must chilled 50F or lower to prevent natural fermentation and spoilage. This practice is widely used within the industry and thought to improve the extraction of color (anthrocyanins) flavor, and aroma. There is, though, some debate among enologists about the overall benefits of this practice. It may be more applicable for pinot noir and zin than other reds. One drawback is that it exposes the juice to bacterial spoilage unless carefully managed.
▪ To minimize problems the must should be sulfited.
▪ Keep the must cold, 50°F or less, preferably closer to 40°F until you are ready to inoculate with yeast. Chill the must with dry-ice, frozen-water-filled jugs, or ice-water bath. Replace frozen water jugs twice a day to prevent complete thawing.
▪ The cold prevents natural yeasts from starting to ferment the juice, and spoilage bacteria from proliferating. In general, allow the must to ‘soak’ for 2 to 3 days or longer to enhance color and flavor extraction.
▪ Many home winemakers skip this step because it’s difficult to chill large containers of juice adequately without something going wrong.
▪ An enzyme should also be used to increase the rate of skin maceration (breakdown), (see Fermentation enzymes for red grapes below).
▪ After a cold soak, allow the must to warm up to above 55°F and then inoculate with the yeast of your choice. You can also allow the natural yeast on the grapes skins to ferment the juice. ‘Natural fermentations’, though, may be slow to start (several days), and bacterial spoilage may begin if you haven’t added enough SO2 to the must or the temperature is much above 55°F. You have to be patient and ignore the smell of VA (volatile acidity), recognized as the smell of vinegar and ethyl acetate (finger nail polish-remover) that may develop before the fermentation becomes vigorous. VA nearly always goes away once the fermentation begins in earnest.
▪ Often near the end of cold soaking you can see tiny bubbles on the surface of the juice ̶ an indication that natural are active. You can promote these by adding fermentation nutrients and not inoculating with a commercial yeast.
▪ Some winemakers argue that extended (post-fermentation) maceration (the practice of letting grape skins and other solids soak in wine following fermentation for an extended period is more beneficial than cold soaking because it softens tannins, making the wine more approachable when young. This topic is discussed later.
Fermentation enzymes for red grapes:
▪ Enzymes are natural protein catalysts that increase the rate of chemical reactions, facilitating the release of pigments, flavors, and aromas. In general, enzymes should be added shortly after crushing.
▪ Add enzymes after SO2 has been added and is well dispersed.
▪ Recommended enzymes:
o Color Pro, Lallzme EX or EX-V (Scott)
o Zym Color, Zym Color Plus (good for increased color) (Enartis)
▪ Other way to improve extraction from grapes: fermentation tannins, cold-soaking, saignée, fermentation temperature closer to max., cap management, extended maceration
Fermentation (sacrificial) tannins: red grapes:
▪ Fermentation tannins are used to reduce oxidation, enhance aromatics, improve mouth-feel, remove unstable proteins, and bind with anthocyanins (pigments) to create more stable color. They bind with grape proteins, preserving more of the softer skin tannins.
▪ Tannins are best added early in the winemaking process, particularly during cold soaking. or at the onset of fermentation. Add the tannin 6 to 8 hours after an enzyme.
▪ Some tannins available for reds:
o Tan FP, Tan Color, Tan Fermcolor, Tan Rouge (Enartis).
o FT Rouge or Rouge Soft (Scott).
o Untoasted oak chips (10 g/gal)
Websites: products;
Fermentation: getting started
White and red grapes for rosé:
▪ Keep juice cool: than 200 but 57ºF. Beta work on wines up to 15 alcohol and up to 60 ppm total SO2. Enartis products include Enoferm ML Silver (alcohol to 15+, pH >3.1, 45 total and 10 free SO2) and Enoferm ML One (alcohol level to 14, pH >3.2, 40 total and 10 free SO2).
▪ Nutrients contained in the light lees that remains after the gross lees is removed at the end of the primary fermentation can often provide adequate nutrients for the developing bacteria. It is important, though, to stir the lees 1 to 2 times a week until MLF is done to keep the dead yeast in suspension, allowing them to release their bound nutrients. If the spent yeast settles and forms a compact cake at the bottom, nutrient availability is reduced. It also serves keep the ML bacteria in suspension and more active.
▪ To ensure that the MLF goes quickly and finishes, use an ML nutrient such as Acti ML or Nutriferm ML, particularly if the MLF is sluggish, or you had a H2S problem during the primary fermentation, or the grapes were very ripe.
▪ Use Acti-ML at the rate of 10 g per hL of wine. Mix in 5 times its weight in chloride-free water at 77°F, and add bacteria. Wait 15 minutes before adding to the wine.
▪ If using Nutriferm ML, add 20 to 30 g of per hL (~25 gal) and dilute in 100 mls of chloride-free water, mix and add to the wine. Hydrate the ML bacteria in the foil packets as recommended by the manufacturer, and add to the wine. The packets contain 2.5g of ML bacteria—enough to treat 66 gallons of wine.
▪ Ideally, the temperature of the wine during MLF should be 68 to 77 for a quick ML conversion. This may require heating a room for several weeks or using an electric blanket to keep the barrel/container warm. Some amateur winemakers use a small aquarium heater inserted into the wine. It’s important that the wire attached to the unit can be securely sealed to prevent oxidation.
▪ CO2 bubbles are released from the wine during the conversion process. If you put your ear to the bung hole you can hear the popping or ‘pinging’ as the bubbles break the surface. As long as the fermentation is active, CO2 gas is being releases and the wine is protected from oxidation. But when the reaction is slowing down and the airlock is being removed frequently to check on the progress, oxidation can occur.
▪ It’s a good idea to purge the air in the head space in the tank or barrel with Argon, CO2 or Nitrogen gas every time you remove the airlock to stir or check progress.
▪ Also keep the container topped to minimize air space.
▪ When you can no longer hear the bubbles popping, test the wine to see if the MLF is done.
▪ It usually takes 3 to 4 weeks, or longer in some cases, to complete, depending on temperature. The warmer it is, the faster the process.
▪ ML fermentations that don’t finish before winter, usually start again the following year when temperatures increase, assuming they are not stored in a cool cellar.
▪ Test to make sure that your wine has completed MLF, because those that have not finished will generally restart in the bottle, resulting in a carbonated wine with off-aromas.
▪ A test reading of 30ppm or less indicates completion.
▪ Sulfite the wine as soon as the wine tests negative for ML.
▪ By the end of MLF, little or no free-SO2 remains, most has volatilized during fermentation or precipitates out in the sediment What remains is bound to various components.
▪ Add 35 to 50 ppm of SO2 to before racking to protect against oxidation.
▪ About ½ of the SO2 added post-fermentation will bind up with components in the wine and become unavailable to do its work.
▪ Check in about a week and adjust to make sure the molecular SO2 is suitable for the pH of your wine.
▪ About 70 to 75% of the SO2 added post-fermentation will be free.
▪ How much additional SO2 is needed will depends on pH, alcohol content. The higher the alcohol, the higher the °B, the higher the pH – the greater the SO2 requirement.
▪ Check the free SO2 a few days after the addition to see your FSO2. (see Topping below)
▪ Eliminate any head space in barrels and other storage containers. This often means breaking the wine down into smaller containers, but this will ensure that the wine will retain most of it aromatic components and that there is less loss of SO2 to the void above the wine.
▪ Red wines are typically racked after MLF, to introduce a little oxygen.
▪ Top the barrel, leaving little or no head-space and use a solid silicon bung to prevent air contact.
▪ For whites, you may want to rack after MLF if the wine is clear or you may opt to age the wine sur-lie. See: Aging wines on the lees (‘sur-lie’) above.
Post MLF SO2 addition for reds:
▪ Add 50 ppm SO2 at the end of MLF for reds and whites. Add 75ppm to whites with a pH above 3.5. Check the pH and TA and adjust as needed.
▪ Wait a couple of weeks, check the SO2 level and adjust, if necessary, to the targeted number.
▪ To avoid an MLF in storage for wines above pH 3.3, consider using Lysozyme or Stab Micro (Enartis), or Bactillis (Scott).
SO2 additions during storage and aging:
▪ Refer to the recommended FSO2 levels based on the wine’s pH listed above in: Use of SO2 to ensure good quality wine.
▪ Determine the baseline (molecular SO2) and avoid deviating from it too much.
▪ Measure FSO2 every 2 to 3 weeks initially, and then monthly for a couple months. Once SO2 levels appear to have stabilized, test every six weeks.
▪ If your SO2 levels are well below the recommended molecular level every time you test, you may not be adding enough SO2 or you need to test and adjust more often.
▪ Keeping the SO2 levels a little higher than what’s recommended for the pH will help avoid levels dipping significantly below the desired level, between SO2 testing. A little cushion will ensure that the wine is adequately protected between additions.
▪ Fewer, larger additions are better than many small ones (it shocks the bacteria more, and the free/total ratio is more favorable.
▪ Keep barrels topped-up to minimize head-space in containers. Wines in cellars with low humidity need to be topped more frequently due to evaporation. Top every 2 to 3 weeks if evaporative loss is more than 6-8 ounces.
▪ If your barrels are tight and develop a strong vacuum when the wine evaporates, you can top less frequently (less exposure to air). Barrels that don’t develop a vacuum, are leaky. I’ve noted that the upper stakes are prone to leaking. Another potential issue is cracks that develop on either side of the bung. You can fill these with barrel wax. Push the wax into the crack and heat with a torch, hair dryer, or heat gun so the wax melts and penetrate the crack further. Another problem is that the silicon bung may not be firmly seated in the bung. It’s also a good idea to check the barrel for leaks in cellars that are open to the outside. Such barrels are prone to lead cable borers that burrow into the wood ― usually the crevice where the curved staves meet the ‘head’ (top flat surface of the barrel).
▪ Because stainless steel tanks are essentially air-tight, FSO2 levels decrease more slowly than in porous oak barrels. unless there is a lot of head-space, or the containers are opened frequently. FlexTanks, made of a special pervious plastic, allow a minute amount of air to interact with the wine.
▪ Purge air that enters a container with inert gas such as Argon each time it’s opened.
▪ Wines can easily lose 10 to 15 parts of SO2 during racking, so it’s important to add additional SO2 preferably before racking.
▪ Check the free SO2 level a few days afterward to see how the wine responded.
Limiting the loss/use of SO2:
▪ Make sure your barrels are clean and don’t leak, and also use a silicon bung.
▪ Check for leaks and top frequently
▪ Purge headspace with inert gas every time you open a barrel or container, or add anything.
▪ Sanitize tools, hoses, stir-rods, pumps, etc.
▪ Add a little SO2 when you add fining agents, other wine-making products to your wine, or oak products: oak chips, cubes, sticks, inserts, etc., The latter add a lot of air to the wine
▪ Air condition your cellar. A temperature of 58°F is ideal for whites and 59 to 63 is ideal for reds. There is at least one electronic device, e.g., CoolBot that can override the thermostat in most air conditioners, allowing them to refrigerate small rooms to the programmed temperature.
Cold stabilization:
Tartaric acid, naturally present in grapes and finished wine, precipitates from solution during fermentation and later during the winter when temperatures drop, or when intentionally chilled or refrigerated. Although wines typically lose much of their Tartaric acid during fermentation, they still contain unstable levels. Excess tartaric acid, unless removed, will crystalize later during storage and after bottling. The crystalized material on the inner surface of carboys, tanks, barrels, and sometimes at the end of the cork or bottom of the bottle is tartaric acid (tartrates) This will continue to drop out of solution until the acid concentration has stabilized.
Chilling or the addition of materials such as bentonite or cream of tartar (potassium bitartrate) can be used to ‘seed’ (cause the ionized acid to combine with potassium ions and form crystallize of potassium bitartrate. Also, the higher the pH and TA, the greater the likelihood of crystallization. This is really more of an aesthetic issue because tartaric acid crystals are harmless, but unsightly, and some people might mistake the crystals for glass.
Unstable tartaric acid can be removed by chilling a wine for an extended period. Allowing the temperature in the cellar to drop to 40°F for 2 -3 weeks, or chilling to 32°F for at least 12 hours, preferably 36 hrs. usually does the job. A spare refrigerator will do the job nicely for wine in carboys. A cold garage in the winter is often sufficiently to facilitate the process in larger containers. The warmer the wine, the longer it takes. Suspending a few grams of Potassium Bitartrate powder will speeds up the crystallization process.
Chilling a wine to even 30 degrees for 36 hours greatly improves Tartrate stability, but it’s not cold enough to completely cold stabilization a wine. Therefore, some wineries may use Gum Arabic (Citrigum or Cellogum) to help stabilize the remaining excess tartrates.
Potassium Polyaspartate marketed by Enartis under the Zenith Uno label stabilizes tartrates in whites and roses. Rate: 100ml/hL. For reds a product is labeled Zenith Color (200 ml/hL
Aging and clarification:
▪ Consider using oak barrels to age and store reds wines and complex white wines like Chardonnay. Used barrels are readily available and relatively inexpensive from local wineries, after bottling they rotate out older barrels. Some are cleaned and treated with sulfur gas, or sometimes ozone―a sanitizer. Others may have simply been drained and rinsed. If they smell ‘off’ (like finger nail polish remover or a bit vinegary) you can look elsewhere, or you’ll need to clean them (See Sanitation above). If they really smell bad, look elsewhere.
▪ Most barrels hold 58 to 59-gal of wine. Enough to fill about 24 cases of bottles. Far more that most couples can reasonably drink within a few years. I suppose you could trade with other winemakers for other varieties. Another approach is to look for several partners or form a co-op of interested people so you don’t have more wine than you can deal with.
▪ To clean a used barrel, soak with Proxycarb: 16 oz / ‘60’ gal barrel and fill with water and let soak for 2 to 24 hrs, depending on severity of the problem. If the barrel smells of VA, let it sit for up to 48 hrs. If it smells dirty, medicinal, of barnyard, discard it or make a planter out of it. After soaking, drain, rinse thoroughly, and add 1T Citric acid in 2.5 gal of water and slosh around the barrel before draining. This will prevent mold and bacteria from growing inside. When storing a used barrel for a short period, let it drain with the bung down. Next, you’ll need to burn a third of a sulfur wick in the barrel or a 5 g disc (pastille). It’s best to use a special stainless-steel basket to hold the wick/tab while lowering it into the barrel, the basket prevents the tab (pastille) from breaking apart and falling into the barrel. Unburned pieces of elemental sulfur inside a barrel can result in H2S problems later. When the sulfur wick or disc is fully burned, removed the basket and bung with a loosely with a Dixey cup or wadded paper towel to prevent the SO2 gas from escaping. In a couple of weeks, check to see if the barrel is dry. And stills smell good. If not burn a second wick.
▪ Avoid inhaling the fumes as they are very caustic and harmful to the lungs
▪ You can occasionally purchase a used 30-gal barrels, or you can order a reconditioned 30-gal barrel from ReCoop in Sebastopol or Barrel Builders in Napa. The problem is that a new or reconditioned barrel can impart too much oak in the wine, so the wine will have to come out early (about 6 months) and be stored in another container, preferably a neutral barrel.
▪ Avoid racking too often. (see: Racking below) Do your final racking just before bottling.
▪ Usually, two racking is fine for reds: once after MLF and just before bottling. For whites 3-racking is preferable: once to remove the heavy lees, the second in the early spring, and the final 4 to 6 weeks before bottling.
▪ Minor adjustments in pH and TA can be made a week or two before bottling.
▪ Smell your wines every time you remove the bung to test, top, or to add something. In this manner, off aromas that develop can be resolved early.
▪ Reduction in wines is one of the most common problems in winemaking. H2S, Mercaptans and other volatile sulfur-based compounds are commonly produced during alcoholic fermentation, but they can also develop during storage and aging, as well as after bottling. The aromas generated by these sulfur compounds are usually described as rotten egg, burnt rubber, skunky, burnt match, asparagus, onion, and garlic, cooked cabbage, etc. (see Reduction: stinky sulfides in red wine above
▪ Reduced (stinky, sulfury smells can develop in aging wine that haven’t been racked, or if H2S was not completely removed after fermentation. Sometimes Revelarom (Enartis) or Reduless (Scott) remedy the problem, or copper can be used as a last resort.
▪ H2S in time will form mercaptans, think onions, garlic, rubber, skunk, etc., and ultimately disulfides which can really undermine taste and smell.
▪ Mercaptans ultimately form disulfides which smells like cooked cabbage, canned asparagus or corn, rubbery, burnt rubber, stagnant water, or even stale, or the agent added to natural gas to give it a smell, so leaks can be detected readily. These chemicals are very difficult to remove.
▪ Keep barrels topped, and purge air space in storage or aging containers with argon gas or other inert gas every time you open to smell, taste, test, top, or add SO2 or other materials.
▪ Whites can be aged in barrels, but will probably undergo MLF, unless the barrels are new or ML-negative the pH is very low and SO2 levels are kept high, or you use a product to inhibit ML bacteria.
▪ Oak cubes, chips, sticks, and barrel-inserts can be used to impart the desired level of oak in the wine held in neutral barrels or other holding vessels.
▪ Toasted oak chips, can be used effectively during aging to impart the aroma and flavor of oak flavor. If used, they should be added after fermentation during storage to enhance aroma and taste. The rate, depending on the type of wine is:
o 0.5-1 g/L for most fresh whites (Sauvignon Blanc, Pinot Gris, Viognier, etc.
o 1 -1.5 g/L for Chardonnay, pinot blanc, etc.
o .5 – 3 g/L for fruity reds such as Pinot noir, Zin, Grenache, etc., up to 4 g/L for cab, petite sirah, syrah, etc.
▪ Use fining agents as necessary to clarify wines, remove haze, browning, or heat-unstable proteins (whites), or reduce sulfur defects, astringency, or bitterness. Do this well before bottling.
▪ You may want to use a polysaccharide product, like Surli Elevage (Enartis) at this point to improve mouth feel, or use a cellaring tannin to improve structure and aging potential, lower the sensation of alcohol, add a sense of sweetness, or a note of vanilla or toasty oak.
▪ Cellaring or finishing-tannins such as Riche (beverage people can be used to add a note of French oak, vanilla, and sweetness, and reduce the sensation of alcohol. Both Scott and Enartis have a number to tannins to choose from: Tan Nature, Tan Rich, Tan Extra, etc. Unfortunately, They’re not cheap! You also have to use them sparingly. A little goes along way.
▪ Gum Arabic can also be added just before bottling to enhance aromas, reduce bitterness and astringency, add body, roundness, and a sense of sweetness.
▪ Cold stabilize wine over the winter. (See Cold Stabilization above).
▪ Aging— bottle fruity whites aged in stainless after 6 to 8 months. Barrel-aged Chardonnay is best after 10-12 months of barrel time. Big reds are best after 18 to 24 months. Pinot noir needs 12 to 14 months in wood.
▪ Filtering whites may be beneficial for whites to improve clarity or remove bacteria. In general, reds are not improved by filtering
Fining:
Fining can be done to make a wine more appealing. It can improve brilliance, aroma and flavor, reduce astringency, bitterness, herbaceousness, and off-aromas, protect from oxidation (browning), and improve filterability. It’s a bit of a tradeoff—depending on what and how much you use. You may lose a bit of character to improve appearance or overall quality. In many cases, the wine are dramatically better.
Fining agents:
Each agent has a specific purpose for removing something from a wine or mitigating a problem:
▪ Ascorbic Acid: (Vitamin C): added as an antioxidant 0.05 to 0.15 g/L (5 to 1.5 #/1000 Gal) works a little better than SO2. Works well for white wines when added before bottling. For Ascorbic acid to work properly you must have significant Free SO2. It can also be used to convert disulfides in wine to mercaptans, which can then be removed with copper, but only in the presence of higher levels of SO2.
o Bentonite: is the recognized treatment to remove unstable proteins in white juice or rosé wine that may settle out later when the wine is warmed or is being cellared. Bentonite is commonly used in low levels for Chardonnay, but at higher levels for wines such as Sauvignon blanc, Pinot gris, Gewürztraminer, and a few others. The use of fermenting tannins, which binds with unstable proteins, minimizing the need for bentonite
o Ideally, Bentonite is added to the juice/must at the start of fermentation. This is thought to result in less stripping of flavors than when added later during storage.
o Rate: 20 to 120 g/hL (26 gal.) (see discussion on Preemptive fining above). Red wines and those high in tannin (polyphenols) are generally stable. White wines, and low tannin reds may have some protein instability issues. Wines fermented or stored in barrels have far less of a problem with protein stability compared to those held in stainless steel.
o The tannins in oak barrels bind with unstable proteins.
o Tannins added to whites before fermentation act as an antioxidant and also serve to remove much of the unstable protein.
o You can test for protein stability by filled a wine-sample vial with a funnel-shaped bottom with the wine, and then heating it with the cap loosely in place in a container of very hot water for 20 to 30 minutes until it cools. Allow the vial to cool 1 to 2 hours before checking it. Unstable proteins will coagulate and settle to the bottom of the inverted cone where they can be seen. Turn the vial on end to check for sediment. If there is sediment, you’ll need to add Bentonite to remove it.
o Mix the Bentonite in water. Allow it to swell and hydrate for 3 hrs. or longer, depending on the formulation. When added to wine, any unstable protein will settle out to the bottom of the container. Add the slurry slowly, while vigorously stirring.. Make sure it is well mixed because Bentonite works on contact.
o Add Silica gel immediately after the Bentonite to facilitate precipitation. It may take a week or more for the Bentonite and protein to settle out. Stir the treated wine the following day to keep the material in suspension and to increase contact time.
o Silica gel: (Silica dioxide, SilFloc, Kieselsol) removes bitter components and is effective counter-fining agent used to speed the precipitation of Gelatins, Isinglass, Bentonite, and other fining agents. It goes in immediately after the other agent. Rate: 25 - 75 ml/hL.
o You can rack off the sediment after several weeks or leave it until you ready to rack.
▪ Clargel (Enartis): removes excessive astringency. Rate: 50 to 150ml/hL. Fine early in the cellaring process.
▪ Claril SP (Enartis): bentonite, PVPP, potassium caseinate, and silica gel. Use for pre-emptive fining. Added at start of fermentation. Rate: 50 to 150 g/hL.
▪ Claril QY (Enartis) yeast hulls and Chitosan. Reduces astringency and bitterness
▪ Colle Perle (Scott): a gelatin that removes excessive astringency. Fine early in the cellaring process.
▪ Copper sulfate: when added to wine, the copper ions chemically bind with undesirable sulfides, e.g., H2S, and mercaptans which settle to the bottom as a precipitate. The reaction occurs quickly and the deodorized wine can then be racked off the lees.
▪ Egg white: used to remove excess tannins and reduce astringency. Rate: I to 4 eggs. Allow 2 weeks of settling before racking.
▪ Fenol (Enartis): an activated charcoal that can reduce the aroma of Brett or smoke taint.
▪ Gum Arabic: more of a stabilizing agent than a fining agent. Use to reduce tartrate formation in refrigerated wines, prevents deposits from forming on the inside of the bottle (red wines), also enhances moth-feel and imparts a slightly sweet sensation.
▪ Gelatins: Used to reduce astringency. Both Scott and Enartis have a number to choose from.
▪ Isinglass (Finecoll: Enartis): a gentle clarification agent that removes bitterness, oxidative and herbaceous character. Highly recommended. Rate: 1 to 4 g/hL (25 gal).
▪ Milk (Non-Fat): 20 to 50 ml/ gal white wines to reduce bitterness, add slight sweetness. Follow with Bentonite Fining. Rack after 4 days, do at least one month before bottling one month prior to bottling.
▪ Milk (whole): 20-50 ml/ gal. to reduce harshness, absorb aldehydes (oxidation). Follow with Bentonite. Rack after 4 days and do at least one month before bottling.
▪ Potassium caseinate: milk protein intended to remove bitterness, oxidation, slight off-flavors, or excess oak flavors. Fine early in the cellaring process.
▪ PVPP: Stabyl (Enartis): removes bitterness, oxidized color.
▪ Sparkolloid ((hot mix): Scott. Can be used to create brilliant white wines, it does not remove heat-unstable proteins. It does not strip character if used in moderation. It can be used after Bentonite as a counter-fining agent to help compact the lees or to remove haze left by other fining agents. It takes at least a week for a cloudy wine to become brilliant. Rate: Hot Mix: 12-48 g/hL/ (26.4 gal) or 2.5-10g/5gal wine or .5g to 2g per gal.
▪ Stab micro (Enartis): Removes spoilage organisms by binding with them and settling out of suspension. The bacterial can be removed by racking and leaving the sediment the sediment behind. This can prevent MLF or remove bacterial that may lead to spoilage, such as ‘Brett’. One formulation can be used at the start of fermentation, while the other is applied later during aging.
Racking:
▪ The sediment that collects on the bottom of carboys, tanks and barrels, following crushing, fermentation of grapes, or aging of wine, should be removed (aging sur-lie is an exception) to improve clarity, ensure aromatic appeal, and stability.
▪ Siphon the clear wine/juice through a flexible clear food-grade hose using the force of gravity or an electric pump to transfer the liquid.
▪ A siphoning tube with a baffle on the end is inserted into the wine down to a point just above the sediment. The baffle prevents uptake of the sediment by drawing the wine from above. In this manner, most of the sediment remains behind.
▪ Make sure everything that siphon system and pump has been sterilized before use.
▪ It’s also a good idea to purge the siphon tube, hose and pump if used with argon or CO2 or NO2
▪ If you’re racking from a stainless-steel container or a barrel, and can’t see the sediment, try to position the siphon tube about an inch above the bottom. Push the tube down to the bottom and pull it up about 1 inch. This should be enough to keep it out of the sediment. If the wine is cloudy when you begin to siphon or pump, pull the tube up a bit until the wine is clear. You can salvage the remaining wine by siphoning most of the wine along with much of some of the sediment or pouring the contents into a gallon jug. The sediment should settle out in 5 to 7 days.
▪ If racking from carboys, tilt the bottle toward you as the wine level drops to raise the level above the siphon tip to increase yield. If you don’t, you’ll lose the siphon because air will be sucked in when there is too little wine above the baffle. For gravity to work, the wine container must be higher than the receiving vessel. This may present a problem for containers larger than 5-gal carboys.
▪ Special lifting devises are available for beer kegs and even full barrels. Barrels on tall racks can be siphoned into carboys, which can then be elevated to siphon the clear wine back into the barrel once it has been racked cleanly.
▪ Winemakers commonly rack 2 time, once after MLF and again before bottling. You may need to rack for other reasons.
▪ Reds can be left on the light lees without racking until just before bottling. The bottom line is to rack if the wine develops off-odors. Racking aerates the wines, usually dissipating most objectionable odors.
▪ Electric pumps are a quick and efficient way to transfer wine. One concern though, is that it aerates the wine to some extent. I displace air in the siphon hoses and pump with argon before pumping my wine. That’s a little tricky.
▪ It’s important to make sure the hoses attached to the pump are tight fitting and do not draw air from the outside. If you see bubbles in the line, starting at the point where the hoses are attached, there is probably a leak, and you need to stop siphoning and make sure the hoses are tight fitting to the barbed-end of the pump inlet and to the siphon tube if used. You may need to use a new length of hose that fits tightly. Sometimes you can cut off the end of a hose that appears flared out by use. Air will be drawn in at these points if they are loose fitting.
▪ If you pump white wines, bubbles may form in the hoses, particularly in the line coming out of the pump. These bubbles are nothing more than CO2 gas coming out of solution due to the agitation.
▪ Even if there are no leaks, some aeration occur will occur because the hose, pump, and filter cartridge (if used), will contain air, unless you purge the air in the system before you start pumping.
▪ Once the hose and pump are filled with wine, there should be no further aeration.
▪ Aeration also occurs when the container empties or when the level falls below the siphon hose and the pump is allowed to run.
▪ It’s important to turn the pump off when the barrel empties and air begins to enter the hose. You can hear this when it occurs and also hear the wine bubbling in the receiving container.
▪ It’s a good idea to add 15 ppm SO2 after pumping to compensate for aeration
▪ The wine near the bottom of the container just above the sediment that can be easily siphoned or pumped can be poured out into a container to settle. You may be able to siphon most of perhaps a bit of sediment at the bottom by lifting on side of the container so that most of the wine collects on one side. Stop as soon as you see the heavy thick sediments. Allow at least a week for the sediment to settle. Rack the relatively clear wine off the sediment. You may need to add some Sparkaloid to clarify the wine if it is a white.
▪ I rack from 60 gal barrels into 15-gal beer kegs for holding prior to bottling. I have a mechanical lift to elevate the wine-filled kegs well above the bottler to ensure adequate siphon flow. In the past, I siphoned wines into food grade plastic carboys for easier handling.
▪ If you are racking back to the original container, you’ll need to add some topping wine to replace the sediment and wine that couldn’t be salvaged.
▪ The exposure to air during racking and pumping and transferring to other containers will cause some of the free SO2 in the wine to bind up with the oxygen or the aldehydes that form. So, it’s a good idea to test for SO2 in a few days and adjust accordingly. It’s best to add 10 to 15 ppm of SO2 as a safeguard and test in a week.
Topping:
▪ ‘Top’ barrels every couple of weeks, or at the very least, monthly, and use an inert gas (Argon) to minimize contact with air. Excess headspace increases the loss of SO2 (volatilization) into the head space. The argon is lost as soon as you open the bung. Acetobacter bacteria and film yeast (a white waxy coating on the surface of the wine) are more likely to develop when there is ample head space, the SO2 level is low, and when oxygen is able to enter through a poorly seated bung or leaks in the barrel.
▪ Use a good quality wine to top with, preferably extra wine of the same variety and vintage. If you have extra wine, bottle some of it, say a case or two, after it has gone through MLF and been racked. You can use it for topping, instead of breaking down containers as you need the wine. You can also use an older vintage or a compatible varietal, as long as it smells and tastes fine. Another option is to buy an acceptably good wine like ‘three-Buck Chuck.’ I mean, how bad could it be?
▪ If you buy an inexpensive wine for topping, make sure that it acceptably good.
Pre-bottling SO2 additions:
▪ test for free-SO2
▪ adjust to the molecular level
▪ only part of the addition will be free — about 70% when added to a clean, dry wine
▪ Let’s say you need to add 18 ppm to achieve the correct level. Some of it will bind up. So, you will need to add ~26 ppm to ensure that your wine is protected. (18 x .7 = ~26ppm)
▪ Remember to account for depletion of SO2 at bottling due to oxygen pickup, depending on how you bottle: under a vacuum or inert gas or exposed to air. (10 to 15 ppm for standard bottlers, and 5 for Enomatic fillers.
▪ Some people can detect SO2 in the aroma when it is above 50ppm free.
Some commercial wineries bottle with as little as 20 ppm, but their sanitation practices are very good. They harvest grapes at night, can chill grapes or juice and keep cellar temperatures very low. In general, they have good control over most factors. They also sterile filter their wines and bottle under inert gas. Their bottles are new and sterilized, and stored at the optimum temperature. But if you’re feeling lucking, go ahead and try it.
Filtering:
Filtering, mostly for whites, is done to help stabilize wines, improve appearance, and, in some cases, taste. Standard 1-micron filters can be used to remove most particulates, a .45 micron filter can be used to remove bacteria and yeast, but may not remove all of them. Nominal filters, which are normally inexpensive, are those that remove most of the particles equal to or greater than the micron rating. Absolute filter (membrane) cartridges, those that remove all particles equal to and larger than its stated micron rating are more reliable, and are available for the standard filter housing used by many home wine-makers. They are about $75 each (MoreWine), but can be used several times after back-flushing. The wines should be very clean before you do a sterile filtering because heavy sediment may render the filter unusable. It’s a good idea to fine (clarify) the wines before filtering them. Isinglass and Sparkloid are two agents that work well to clean up the wine before sterile filtering. Sterile filtering can be used to prevent ML in the bottle or protect a wine with residual sugar, remove Brettanomyces, or just polish a wine. Unless there is a bacterial problem, most reds, if needed, can be filtered with nominal filters, 1 micron is good. Absolute filters are best suited to white wines. There is not much evidence to support the claim that filtering strips a wine of its character. This claim is not supported by research and many commercial winemakers are split on the issue. However, for big reds, filtering may disrupt wine structure temporarily. Absolute filtering for reds may actually remove some of the polymerized particles that are important for structure and roundness. In general, filtering improves appearance and doesn’t appreciably affect taste of aroma wine, and in most cases it improves quality.
Bottling:
When you’re satisfied with the clarity, acidity, mouth feel, taste, and aroma of a wine, you’ve made your adjustments, and the wine is stable, it’s time to bottle.
▪ Agitate white wines aged in carboys or tanks that are still gassy to remove the dissolved CO2
▪ Adjust SO2 to targeted level and remember to account for depletion of SO2 at bottling due to oxygen pickup, depending on how you bottle.
▪ Clean and sanitize your bottles
▪ Allow no more than about ½-inch of headspace (under the cork) in the bottle
▪ Purge the air headspace with Argon, or Nitrogen before inserting the cork
▪ Fill the bottles with a gravity filler or by other means, but avoid splashing the wine when filling bottles.
Other resources:
Fermentation Handbook from Scott Labs
White wine-making guide available from
Helpful numbers: conversions
1 pound per 1000 gal, = .012 g/l or .453 g/gal
1 egg white = ~30 g
1 g = largely to 1 ml
1 ml =.001 liter (l) or there are 1000ml in 1 liter
1mg in I liter = 1ppm (ppm can be converted to mg/l by multiplying it with 0.998859).
1 pound = 453 g
1 ounce = 29.4 ml. To convert mls to ounces, multiply by .0338) or divide by 29.4
1 gal =3.785 l(liter)
1 T = .5 oz or 14 g
1 T = 3 tsp
1 tsp = 5 ml
1hl (hectoliter) = 26.4 gal
1 liter = 0.26 gal
1 gallon = 3.785 liters
1 kilogram = 1000 g or 2.2 pounds,
1 gram = 0.0353 ounces 1 milliliter (ml) = 0.2 tsp
1 tsp = 5 ml
1.0 g/L
= 0.10 g/100 mL
= 100 g/hL
= 100 mg/100 mL
= 1000 mg/L
= 1000 ppm
= 1.0 mg/mL
= 1000 µg/mL
= 0.1% (wt/vol)
1 lb/1000gal
= 454 g/1000 gal
= 0.45 g/gal
= 0.12 g/L
= 120 ppm
= 12 g/hL
To convert °C °Farenheit... multiply by 1.8 and add + 32
or 9/5 C +32
Appendix:
Disassociation of Tartartic acid (pKa’s)
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