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Learning activity 3Heating of green vegetablesObjectiveTo examine the colour and texture changes of boiled green vegetables with different pH conditions.PrincipleChlorophyll stability is affected by pH condition. Heating of vegetables will cause acid in cells to be released to the cooking medium. Chlorophyll will be converted to pheophytin. The colour changes from bright green to dull olive brown.Equipment & materialsEquipmentMaterialsScaleSaucepanTimerGreen vegetables 100 g x 3 (300g)Sample A:Water 200mlSample B:Water 200mlBaking soda ? tspSample C:Water 200mlVinegar 1 TbspProcedure Prepare the three samples.200ml water200ml water + ? tsp baking soda200ml water + 1 Tbsp vinegarBring the samples to the boil.Add 100g vegetables to each sample and cook for another 4 minutes.Record the colour and texture of cooked vegetables in different samples.Results Cooking mediumColour of cooked vegetablesTexture of cooked vegetablesWater onlyWater + baking sodaWater + vinegarQuestionsWhich cooking medium significantly changes the colour of green vegetables? Explain.Which cooking medium can speed up the breakdown of cellulose and produce a softer texture?What happens if cooking the vegetables in an alkaline medium for too long? ................
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