Determination of Optimum Maturity Index of Mango Fruits ...

AGRICULTURE AND BIOLOGY JOURNAL OF NORTH AMERICA

ISSN Print: 2151-7517, ISSN Online: 2151-7525, doi:10.5251/abjna.2014.5.2.97.103 ? 2014, ScienceHu,

Determination of Optimum Maturity Index of Mango Fruits (Mangifera indica, L.) in Darfur

Omer Khidir Ahmed1* and Soad El Tayeb Ahmed2

1Department of Horticulture, University of Khartoum, Sudan. Current address: Department of Biology, Faculty of Science, Taif University, P.O. Box 888, Taif 21974, Saudi Arabia. Mobile: 00966542081158 Fax: 00966 2 734 2175 2Department of Horticulture, Western Darfur State, El Geniena, Sudan

ABSTRACT

Mangoes produced in Darfur, Sudan are either sold locally at low prices or lost due to poor transportation and storage facilities. Harvest maturity of 'Kitchiner', 'Alphonse' and 'Dibsha' mango (Mangifera indica, L.) cultivars grown in Darfur were studied to reduce such losses. Optimum date for harvesting was determined to extend the postharvest life. Fruit weight, specific gravity, titratable acidity, pH, total soluble solids (TSS) and the number of days from flowering to maturity were studied to fix some maturity indices. Titratable acidity, pH, TSS and number of days for ripening were found suitable maturity indices for harvesting. Fruit weight was cultivar dependent and could be used for harvesting 'Dibsha' and 'Alphonse' only. Specific gravity showed no positive trend as a maturity index. Interactions of maturity indices indicated that the optimum date for harvesting 'Kitchiner', 'Alphonse' and 'Dibsha' were 15 and 16, 16 and 17 weeks after flowering, respectively. Keywords: Mango; Mangifera indica; Maturity; index; Darfur.

INTRODUCTION

Mangoes are grown in tropical and subtropical regions of the world with India leading world production. The fruit is considered the King of all fruits. Besides, the fruit is rich in antioxidants and, therefore, reduces the risk of cardiac disease, anti cancer and anti viral activities (Daud et al., 2010). Chemical composition of mango fruits differs with regard to different cultivars and area of production (Hulme, 1971; Abbasi et al., 2011). In Sudan, mangoes are both popular and valuable fruits. The success of mango cultivation in Sudan could be attributed to the diverse environmental conditions across the country, which extends the fruiting season to eleven months a year (Saeed et al., 1975; El Mahdi and El Awad, 1984). In some areas of Darfur mangoes bear fruits twice a year. Due to poor transportation and storage facilities, mangoes produced in remote areas of Darfur are sold at very low prices compared to prices offered in Khartoum. To help rectify this situation, the possibility of harvesting mango fruits at optimum maturity to extend the shelf-life of the fresh produce was explored.

The quality as well as the postharvest life of the fruit is influenced by the stage of maturity at harvest

(Anjum et al., 2006; Jha et al., 2007). However, proper quality, taste and flavor of mango can only be assured when fruits are harvested after attaining physiological maturity (Reid, 2002; Slaughter, 2009). The physiological and biochemical activities of over mature fruits differ from that of mature ones in terms of respiration rate, transpiration, conversion of starch to sugars and storage life (Hulme, 1971; Kader et al., 2002).

Maturity standards based on physical and chemical parameters must be enforced to assure that only high quality fruits are harvested (Pal et al., 1987; El-Buluk et al., 1995; Lebrun et al., 2008) Physical indices of maturity such as weight, size, shape, external color, number of days from bloom to harvest, specific gravity and fruit pressure are used as criteria for harvesting different fruits (Malevski et al., 1977; Jha et al., 2006; Dick et al., 2009). Jha et al. (2006) reported that maturity of mango could be predicted by measuring size, color and firmness. Chemical standards used in the assessment of maturity at harvest include TSS, total acidity and pH, acid/sugar ratio, reducing sugars, tannins, volatile substances, ascorbic acid, internal color of the flesh and oil content (Hulme, 1971; El-Buluk et al., 1995; Kader, 2002; Abbasi et al., 2011).

Agric. Biol. J. N. Am., 2014, 5(2): 97-103

The number of days from flowering and fruit set to harvest was found to be a good nondestructive maturity index for many fruits such as bananas (Ahmed, 1997), guava (El-Buluk et al., 1995), melons (Ahmed, 2009b), strawberry (ElMasry et al., 2007) and mangoes (Hofman et al., 1977; Pal et al., 1987; Lebrun et al., 2008; Slaughter, 2009; Dick et al., 2009). Solids and acids data indicated that lateharvested fruits resulted in sweeter fruits and had a different volatile profile from earlier-harvested fruits (Lebrun et al., 2008). Dick et al. (2009) indicated that mangoes collected 100 days after flowering developed better organoleptic characteristics than those harvested earlier under conditions of North Cote d'Ivoire, and concluded that fruits developed best qualities during ripening. Bagging the cultivar `Keitt' at 131, 105, 82, 56 and 31 days before harvest improved fruit quality through reduction in Colletotrichum and Dothoriella spp diseases (Hofman et al., 1977).

Specific gravity has certain advantage over other criteria in determination of maturity, since it is nondestructive and easy to apply. Pal et al. (1987) concluded that specific gravity of about 1,02 was a good maturity index. However, fruit size and sphericity decreased due to shrinkage during growth and storage (Jha et al., 2006).

Skin color was used as a maturity index in harvesting mangoes (Hulme, 1971; Malevski et al., 1977; Anjum et al., 2006; Jha et al., 2006; Abbasi et al., 2011), citrus (Ahmed, 2009a) and avocado (Maru et al., 2011). Malevski et al. (1977) reported that both, maximum red and maximum yellow color intensities at harvest, could serve as a good index of maturity in mango, and concluded that maximum red coloration was found to be a more sensitive maturity index than the maximum yellow coloration. However, the appearance of red color on the skin (in some cultivars) is not a reliable index of maturity. Likewise, the change in skin ground color from dark-green to light-green or yellow is not reliable because of variations between cultivars.

Skin color measured by colorimeters and spectrophotometers are used to predict maturity index and ripeness in mangoes (Malevski et al., 1977; Schmilovitch et al., 2000; Jha et al., 2006; Jha et al., 2007; Lebrun et al., 2008). Using the nearinfrared (NIR) spectrometry, in the spectral range of 1200-2400 nm, Schmilovitch et al., (2000) was able to nondestructively assess maturity factors (including: TSS, acidity, firmness and storage period) in the cultivar `Tommy Atkins'. Jha et al. (2007) explored a

nondestructive method for predicting maturity using color values taken by a handheld HunterLab colorimeter. Mature fruits could ripe with highsatisfied taste while fruits predicted to be immature or over mature were mostly rejected by the panels (Jha et al., 2007). Using the electronic nose (enose) or gas chromatography (GC) for aroma and other volatiles as well as for soluble solids and acids, Lebrun et al. (2008) indicated that mango fruit volatiles may be useful as maturity markers to determine optimal harvest maturity for mango fruit that results in full quality upon ripening.

This study was designed to asses the optimum maturity indices for harvesting mango fruits in Darfur to withstand handling, transportation, storage and to extend the postharvest life. Data obtained were correlated with harvesting date, which was taken as the independent variable.

MATERIALS AND METHODS

Plant Material: Mango fruits of 'Kitchiner', 'Alphonse' and 'Dibsha' cultivars were obtained from trees grown in an orchard located in 'Kajja' Valley at El-Geniena area, Western Darfur State, Sudan. Mango trees of each cultivar were uniform in appearance and vigor. All trees received the same cultural practices and a single application of farm manure applied annually following harvest and prior to the beginning of the rainy season.

Preparation of Fruit Samples: Tagging of 50 inflorescences in each tree was made using a label showing dates of flowering. Care was taken to obtain fruits of similar size and skin color as an indication for visual analysis. A sample size consisting of 20 fruits from five trees (= 4 fruits/tree) of each cultivar were picked at weekly intervals. Sampling started 12 weeks after flowering. Eight, 9 and 10 samples (harvests) were taken from 'Kitchiner', 'Alphonse' and 'Dibsha', respectively. Sampling continued until fruits started to ripen on the trees. At each harvest date, the fruits were handpicked from all over the tree by a clothbag attached to a long pole. Only uniform and green fruits were selected. Selected fruits of each cultivar were combined and divided into two lots of 10 fruits each. One lot was analyzed as fresh fruits for weight, specific gravity and chemical characters to determine total soluble solids, pH and titratable acidity.

The other lot was analyzed, after ripening under laboratory conditions, to determine physical and chemical characteristics and the number of days required for ripening of the fruits. Fruits of the second

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lot were kept in baskets made from 'Doom palm' leaves (Hyphaene thebaica). Baskets were lined with grass and the fruits were also covered with grass. Ripening took place at room temperature of 30-35 ?C. Fruits were inspected daily for visual change in color (from green to yellow) and pressed manually for flesh firmness.

Analytical Procedures:

Fruit weight (g): A top loading sensitive balance was used for measuring total fruit weight in grams (g).

Specific gravity: Measured by weighing the fruits first in air and again in water using a top sensitive balance to determine the volume of the fruit.

Number of days required for ripening of the fruits: The period required for ripening of fruits kept in baskets was calculated by taking the average period required for all the fruits (10 pieces) to reach ripening.

Titratable Acidity: Titratable acidity measured as % citric acid of fresh mango juice was determined by titrating the sample to pH 8,2 with 0,1 N sodium hydroxide (NaOH) as described by Ranganna (1979).

pH value: The pH of mango juice was measured by a Griffin pH meter model 40.

Total Soluble Solids (TSS): The total soluble solids (Brix) of fresh mango juice was measured by a Kruss hand refractometer model HRN-32.

Experimental Design: Sampling of fruits from the orchard was made in a completely randomized design. Data obtained from measuring physical and chemical characteristics were correlated with harvesting date, which was taken as the independent variable.

RESULTS AND DISCUSSION

The degree of shrinkage in 'Kitchiner' and 'Alphonse' decreased as picking time advanced (Tables 1 and 2). After 15 weeks from flowering, there was 10% of shrinkage in fruits. No shrinkage was observed after the 4th harvest. In 'Dibsha' shrinkage continued until the 5th harvest (Table 3). The occurrence of shrinkage is natural during the first weeks of fruit growth, due to moisture loss (El-Buluk et al., 1995). This is consistent with Jha et al., (2006) report on decrease of size and sphericity due to shrinkage.

The weights of both hard and ripe 'Kitchiner' fruits did not show specific trend of change (Table 1) and no significant correlation between fruit weight and harvesting date was recorded (Table 4). However,

significant correlations were found between fruit weight and harvesting date in 'Alphonse' (Table 5) and 'Dibsha' (Table 6) cultivars. The weight of hard and ripe 'Dibsha' fruits increased as the picking season advanced (Table 3). This is expected as the weight of 'Dibsha' fruits is generally greater than the other two cultivars. Dick et al. (2009) indicated that the time to ripen and weight loss continuously decreased with fruit maturity in the cultivar 'Kent'.

Specific gravity of both hard and ripe fruits of the three cultivars showed fluctuating patterns of increase and decrease with regard to harvest time, without any significant correlations (Tables 4, 5, and 6). However, hard and ripe fruits of all cultivars scored an average of > 1,05 specific gravity with 'Alphonse' scoring 1,10 on the 19th week from flowering. A specific gravity of about 1,02 was considered a good maturity index for mangoes (Pal et al., 1987).

Highly significant positive correlations were found between TSS and harvest date in the three mango cultivars (Tables 4, 5, 6). This is in agreement with results in North Cote d'Ivoire (Dick et al., 2009). Total soluble solids of both hard and ripe 'Kitchiner' and 'Dibsha' cultivars tended to increase as the harvesting date progressed (Tables 1, 3). However, a decrease in TSS of both green and ripe 'Alphonse' cultivar was noted on the 4th harvest, but continued to increase again thereafter (Table 2). The highest levels of TSS were reached after 17 to 18 weeks in 'Kitchiner', 18 to 19 weeks in 'Alphonse' and 19 to 20 weeks in 'Dibsha'. Similarly, Dick et al. (2009) reported that mangos collected at 100 days after flowering developed better sugar content and other organoleptic characteristics than earlier harvested fruits. Using the enose and GC for soluble solids Lebrun et al. (2008) indicated that later harvest maturities resulted in sweeter fruits. Jha et al. (2007) measured TSS by a handheld refractometer and computed, with a HunterLab colorimeter, that fruits predicted to be mature could ripe with high-satisfied taste.

Increase in pH values were observed in 'Kitchiner' and 'Alphonse' cultivars as the harvest season progressed (Tables 1, 2). In 'Dibsha', however, the pH tended to increase upto 16 weeks from flowering, then decreased at 17 weeks and again started to increase until the fruits ripened on the tree (Table 3). Significant positive correlations between pH values and harvest date were found in all cultivars (Tables 4, 5, 6). The pH has been correlated to maturity index in mango (Hulme, 1971; Lebrum, 2008; Dick et al.,

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Agric. Biol. J. N. Am., 2014, 5(2): 97-103

2009; Schmilovitch, 2000; Hakkim et al., 2012) and respectively. Significant negative correlations were

strawberry (ElMasry et al. 2007). Using NIR noted between the number of days required for

spectrometry, Schmilovitch et al. (2000) was able to ripening and the harvest date of the three cultivars

nondestructively assess acidity as a maturity factor of (Tables 4, 5, 6). Dick et al. (2009) indicated that the

mango fruit. Titratable acidity correlated positively time to ripen continuously decreased with fruit

with maturity in mango cv. 'Kent' (Dick et al., 2009). maturity. Their data correlated to maturity stages

Hakkim et al. (2012) showed that citric acid corresponding to fruit harvests carried out at 76, 82,

maintained apple slices at acidic condition for 10 88, 94 and 100 days after flowering (Dick et al.,

days.

2009). Coatings delayed mango fruit ripening and

The number of days required for 'Kitchiner', 'Alphonse' and 'Dibsha' fruit ripening, under laboratory conditions, decreased as the picking season progressed (Tables 1, 2, 3). However, 'Dibsha' fruits harvested on the 12th week after flowering did not show any sign of ripening, but shrank and dried after three weeks (Table 3). Fruits of 'Kitchiner', 'Alphonse' and 'Dibsha' required 7, 7 and 9 days to ripen at room temperature,

improved keeping quality and extended storage life with appreciable retention of all quality parameters (Anjum et al., 2006; Abbasi et al., 2011). According to Abbasi et al. (2011) best results were exhibited by Carboxy Methyl Cellulose (CMC) at 2%. Bagging the cultivar `Keitt', at 100 days before harvest, shortened the days to ripen at 22?C (Hofman et al., 1977). However, Njoku et al. (2011) attributed losses in ascorbic acid to its sensitivity to oxidation at high temperature.

Table 1: Measurements of shrinkage %, fruit weight, specific gravity, total soluble solids (TSS), pH

value, and number of days required for ripening of 'Kitchiner' mango fruits as influenced by harvest

date.

Harvest date after flowering (weeks)

Shrinkage (%)

Average wt. (g)

Specific

gravity TSS

(?Brix) pH value

Number of days for ripening

hard

Ripe hard

Ripe

Hard Ripe hard

12

80

13

40

14

30

15

10

16

0

17

0

18

0

19

0

176

112 0,97

0,70

9

17

2,6

9

186

138 0,99

0,96

10 16

2,7

8

288

235 1,05

1,02

10 17

2,85

8

244

143 0,96

0,93

12 19

2,8

7

198

162 0,99

1,02

15 20

3,0

7

194

147 0,99

1,01

17 20

3,27

6

205

171 1,01

1,03

18 22

4,15

3

-

210 -

1,03

-

20

4,40

0

100

Agric. Biol. J. N. Am., 2014, 5(2): 97-103

Table 2: Measurements of shrinkage %, fruit weight, specific gravity, total soluble solids (TSS), pH value, and number of days required for ripening of 'Alphonse' mango fruits as influenced by harvest date.

Harvest date after flowering (weeks)

Shrinkage (%)

Average wt. (g)

Specific

Gravity TSS

(?Brix) pH value

Number of days for ripening

Hard

Ripe

Hard

ripe

Hard ripe

hard

12

100

165

115

1,08

1,06

11

17

2,27

12

13

60

180

135

1,07

1,06

12

19

2,39

10

14

30

245

194

1,07

1,03

12

19

2,75

9

15

10

198

148

1,03

1,03

11

18

2,60

9

16

0

225

208

1,04

1,03

13

20

2,80

7

17

0

221

181

1,06

1,05

15

20

2,80

8

18

0

238

214

1,08

1,03

17

22

2,95

7

19

0

249

225

1,09

1,10

17

22

2,45

5

20

0

-

230

-

1,08

-

20

3,84

0

Table 3: Measurements of shrinkage %, fruit weight, specific gravity, total soluble solids (TSS), pH value, and number of days required for ripening of 'Dibsha' mango fruits as influenced by harvest date.

Harvest date after flowering (weeks)

Shrinkage (%)

Average wt. (g)

hard

ripe

Specific hard

Gravity TSS

(?Brix)

pH value

Number of days for ripening

ripe

Hard ripe

hard

12

100

13

100

14

80

15

30

16

10

17

0

18

0

19

0

20

0

21

0

316

-

0,94

-

8

-

2,40

-

355

262

0,98

0,99

9

13

2,37

15

448

323

0,99

0,98

8

14

2,40

12

428

363

1,03

1,00

10

15

2,45

10

374

335

1,05

1,07

13

17

2,65

8

463

387

1,07

1,00

13

17

2,60

9

488

433

1,01

1,00

14

17

2,80

7

565

500

0,95

1,00

15

18

2,80

7

511

480

1,00

1,04

15

18

2,97

6

-

488

-

1,07

-

17

3,70

0

Table 4: Correlation coefficients between harvest date after flowering and physico-chemical factors of hard mango fruits taken from 'Kitchiner' cultivar.

Factors correlated

Average weight Specific gravity Total soluble solids (TSS) pH value Number of days for ripening

a Not significant b Highly positive significant c Highly negative significant

Correlation coefficient (r)

Hard Fruit 0,004 a 0,26 a + 0,98 b + 0,91 b - 0,91 c

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Table 5: Correlation coefficients between harvest date after flowering and physico-chemical factors of hard mango fruits taken from 'Alphonse' cultivar.

Factors correlated

Average weight Specific gravity Total soluble solids (TSS) pH value Number of days for ripening a Not significant b Highly positive significant c Highly negative significant d Significant

Correlation coefficient (r)

Hard Fruit

0,74 d 0,48 a + 0,93 b + 0,93 b

- 0,90 c

Table 6: Correlation coefficients between harvest date after flowering and physico-chemical factors of hard mango fruits taken from 'Dibsha' cultivar.

Factors correlated

Average weight Specific gravity Total soluble solids (TSS) pH value Number of days for ripening a Not significant b Highly positive significant c Highly negative significant

Correlation coefficient (r)

Hard Fruit

0,83 b 0,40 a 0,97 b 0,86 b - 0,93 c

These results will aid in harvesting mango fruits at optimum maturity to extend the shelf-life and overcome poor transportation and lack of storage facilities in Darfur. A handheld refractometer and a HunterLab colorimeter is recommended to assess maturity index of mango in remote areas of Darfur. It is further suggested that surplus production of mango in Darfur could be preserved into fruit slices (Ahmed and Ahmed, 2012) without loss in color, flavor and microbial growth. Hashmi et al. (2007) showed that mango pulp samples treated with 0.2% potassium metabisulphite and packed in plastic containers had negligible microbial growth, maintained maximum nutrients stability and had best quality characteristics during storage.

CONCLUSIONS

'Kitchiner' mango cultivar could be harvested between 15 and 16 weeks after flowering. During this period, values of TSS of hard fruits were between 12 and 15 ?Brix and pH values were between 2,80 and 3,00. 'Alphonse' cultivar could be harvested after the 16th week of flowering. At this time, values of TSS were 13 and 20 (?Brix) for green and ripe fruits, and the pH value for green fruits was 2,80. "Dibsha"

cultivar could be harvested after 17 weeks from flowering. During this period the TSS of hard fruits was 17 ?Brix, and the pH was 2,6.

REFERENCES

Abbasi, K.S., Anjum, N., Sammi, S., Masud, T. and Ali, S (2011). Effect of coatings and packaging material on the keeping quality of mangoes (Mangifera indica L.) stored at low temperature. Pakistan J. Nutr. 10(2): 129138.

Ahmed, O.K (1997). Effect of ethrel on banana fruit ripening. U. Khartoum J. Agric. Sci. 5(1): 80 ? 92.

Ahmed, O.K (2009a). Sugar regulation of plastid reversion in citrus epicarp is mediated through organic acid metabolism. Pakistan J. Biol. Sci. 12(3): 246-251. (Doi: 10.3923/pjbs.2009.246.251).

Ahmed, O.K (2009b). Evaluation of objective maturity indices for muskmelon (Cucumis melo) cv. 'Galia'. J. King Abdul Aziz U. Sci. 21(2): 317-326. (Doi: 10.4197 / Sci. 21-2.9).

Ahmed, O.K and Ahmed, S.E (2012). Preservation of Mango Fruit (Mangifera indica, L.) Slices in Darfur. Pakistan J. Nutr. 11(7): 583-590.

Anjum, N., Masud, T and Latif, A (2006). Effect of various coating materials on keeping quality of mangoes (Mangifera indica) stored at low temperature. Am. J.

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