تأثير بعض المعاملات الطبيعية قبل الجمع على المحتوى المعدنى والمحصول والجودة والقدرة التخزينية لثمار المانجو

                                                "Effect of Some Natural Preharvest Treatments on Mineral Content, Yield, Fruit Quality and Storability of Mango Fruits

This investigation was carried out during two consecutive seasons (2003 and 2004) on two mango cultivars; i.e. “Alphonse” and “Badami” (Mangifera indica L.). The experimental trees were eighty years old budded on Balady mango rootstock, grown at Daraneet orchard, Kafr El- Dawar Beheira- Governorate.

The objective of this research was to evaluate the effect of some preharvest natural treatments on mineral content, yield, fruit quality and storability of “Alphonse” and “Badami” mango cultivars.

Thirty- three trees, as uniform as possible, were chosen for each cultivar. They were divided into eleven groups, and each group received one of the different treatments. The treatments were arranged in a randomized complete block design, in which each treatment was represented by three, one tree, replicate.

Each treatment was surrounded by buffer trees. The eleven treatments were as follows:

•             Untreated trees (control)

•             Calcium chloride (0.5, 1.0 and 1.5 %

•             Ascorbic acid (200, 300 and 400 ppm)

•             Citric acid (200, 300 and 400 ppm)

•             Active dry yeast (3g/l)

The first application was at full bloom, fruit set and three weeks before harvest.

At harvest time, leaf samples were taken from spring growth cycle, previously tagged in March of both seasons, from non- fruiting shoots. In the same time, three fruits from each replicate (tree) were picked. Mineral content was determined in the leaves and the fruit peel and pulp. The average yield as kilogram per tree was also determined. At harvest, sound fruits were randomly selected, washed and dried. Initial sample of three fruits were taken from each replicate and examined to determine the physico-chemical properties and the remaining fruits were stored at 10oC, 85- 90% relative humidity for thirty days.

During storage period, samples of three fruits were taken from each replicate on a time scale of 0, 6, 12, 18, 24 and 30 days from beginning of storage. In the initial sample, fruit weight and fruit peel, pulp and seed weights were determined. In each fruit sample, fruit weight loss, fruit firmness, carotenoids, total soluble solids, acidity, ascorbic acid, reducing and non- reducing sugars, total sugars, starch, water soluble pectin, total phenols, peroxidase and polyphenoloxidase were determined. The results obtained in this study could be summarized as follows:

1. Mineral content

-              During both experimental seasons, in both “Alphonse” and “Badami”, calcium chloride at 0.5, 1.0 and 1.5 % increased the leaf manganese content, while potassium was markedly decreased. Whereas, the magnesium content in leaf and fruit peel and pulp decreased and calcium content increased.

-              Calcium chloride treatments seemed not to influence greatly the concentrations of leaf N, P, Fe, Zn and Cu, as well as, N, P, K, Fe, Mn, Zn and Cu in peel and pulp.

-              During both experimental seasons, in both “Alphonse” and “Badami”, both the two antioxidants (i.e. ascorbic acid and citric acid) and active dry yeast treatments generally improved nutritional status but the significance was observed in leaf N, P, K, Fe, Mn, Zn and Cu and N, P in peel.

2. Yield and fruit quality

-              In both mango cultivars, the two antioxidants (i.e., ascorbic acid and citric acid) at 200, 300, and 400 ppm and active dry yeast (3 g /l) increased the yield as kilograms/tree, fruit weight, peel, pulp and seed weights, reducing sugars, non- reducing sugars and total sugars and this increment was related with the increasing the concentration of the applications. On the other hand, calcium chloride treatments at 0.5, 1.0, and 1.5 % had no effect.

-              All natural treatments increased pulp firmness, percentage of T.S.S. content, ascorbic acid, starch and total phenols content. Meanwhile, the three calcium chloride treatments and active dry yeast application offered the firmer fruits compared to the two antioxidants. T.S.S. content increased with increasing the concentration for all treatments, also vitamin C content increased by increasing the concentration and 1.5 % calcium chloride treatment which recorded the highest value. Trees treated with calcium chloride treatment at 1.0 and 1.5 % produced the highest starch percentage compared to other treatments.

-              In both mango cultivars, all natural treatments decreased the pulp water soluble pectin and both peroxidase and poly phenoloxidase activities, meanwhile, the two higher concentrations of calcium chloride treatments (1.0 and 1.5 %) caused the lowest value.

-              In both cultivars, all natural treatments did not affect the pulp carotenoids content.

-              In both cultivars, calcium chloride treatments at 0.5, 1.0 and 1.5 % produced high percentage of acidity compared to control. On the other hand, the two antioxidants (i.e. ascorbic acid and citric acid) at 200, 300 and 400 ppm and active dry yeast treatments reduced the fruit acidity compared to control.

3. The fruit physico-chemical changes during cold storage

-              In both experimental seasons in “Alphonse” and “Badami” cultivars, weight loss percentage, carotenoids, T.S.S., reducing sugars, non reducing sugars, total sugars, water soluble pectin, peroxidase and polyphenoloxidase  increased progressively through the storage period, whereas, fruit firmness, acidity, ascorbic acid, starch and total phenols decreased in both cultivars.

-              During storage period, fruit of both “Alphonse” and “Badami” mangoes treated with calcium chloride at 0.5, 1.0 and 1.5 % decreased fruit weight loss, firmness, carotenoids, water soluble pectin, peroxidase and polyphenoloxidase activities, while the total soluble solids, acidity, ascorbic acid, starch and total phenols content increased as compared to control. However, reducing sugars, non- reducing sugars and total sugars were not greatly affected during storage time.

-              During storage period, fruit of both “Alphonse” and “Badami” mangoes treated with ascorbic acid or citric acid at 200, 300 and 400 ppm, in addition active dry yeast treatment (3g/l) decreased fruit weight loss, firmness loss, acidity, water soluble pectin and peroxidase and polyphenoloxidase activities compared to control. In contrast, total soluble solids, ascorbic acid, reducing sugars, non- reducing sugars, total soluble sugars and starch content increased compared to control. However, pulp carotenoids content were not greatly affected during storage time."