الفهرس 
Introduction
DistributionOnly 14 pages are availabe for public view
 |  | from | 32 |  |  |
| | | from | 32 | | |
Abstract
Experimental work: The experiment was executed at the experimental orchard and the laboratories of fruit section and central plant physiology at Faculty of Agriculture, Assiut University throughout two successive seasons of 2012 and 2013. The experiment included three pomegranate cultivars named as Manfalouty, Hejazy and Nab-El-Gamal in a complete randomized design. Five fruits from each tree wee periodically sampled at six growth phases beginning from 1st August till 15th of October at 15 days intervals. The samples were picked and transferred directly to the laboratory of fruit section, Faculty of Agriculture, Assiut University to determine:
1 - Physical properties: Fruit dimensions (Height and Diameter); fruit weight (g); fruit peel and arils weight (g).
2 - Chemical properties: Total soluble solids percentage (T.S.S.) were estimated by using the hand refractometer (ATAGO N-IE); Total acidity was determined by titration of NaOH at 0.1N using phenolphthalene as an indicator. The NaOH was adjusted by using a known volume of oxalic acid 0.1M according to A.O.A.C. (1984). TSS/acid ratio was then calculated. Sugars: reducing and total sugars were determined according to Lane and Eynon method as outlined in A.O.A.C (1984).
3 - Antioxidant content:
Antioxidant contents in the current study included ;Vitamin C (Ascorbic acid) ; Total phenolic content (T.P.C.) of peel and juice; Hydrolysable Tannin content (H.T.C) of peel and juice and total anthocyanin content (T.A.C.) of peel and juice were determined.
Data were analyzed as a factorial experiment (6x3). The analysis of variance (ANOVA) was applied according to Snedecor and Cochran (1989). Means were compared using the L.S.D. values at 5% level of the probability.
Results:
1 - Physical properties: Data revealed that there was a progressive increase in fruit weight. Generally, the average fruit weight in the first season at any measurement period was less than the second season due to the heavier bearing in the first season of study than the second one.
Concerning the peel weight, the second season recorded much higher peel weight compared to the first one. The peel weight was 66.2, 62.9 and 68.4 g during the first season while it was 152.5, 147.0 and 142.8g during the second season for Manfalouty, Hejazy and Nab-El-Gamal cultivars; respectively. The significant differences were found between Nab-El-Gamal and Hejazy in the first season and between Manfalouty and Nab-El-Gamal during the second season.
Concerning the arils weight there were significant differences between the cultivars during the two seasons except of Manfalouty and Nab-El-Gamal in the first season.
Fruit dimensions (height and diameter) increased steadily till 120 DAFB in the first season and 135 DAFB in the second one, and then they slowly increased till the fruits reached the maturity. The growth of pomegranate fruit follows the sigmoid curve. The increase of fruit size and weight is due to the increase of arils size and juice content, as well as the peel growth during different growth phases. The results of current study showed a significant increase in the fruit weight as well as peel and arils weight during different growth phases and reaching the highest value at fruit maturity. Our study also indicated that both fruit diameter and height increased during the initial phases of development and then the rate of size growth slowly increased.
2 - Chemical properties:
The results indicated that Manfalouty cultivar had the highest TSS content compared to the other two cultivars. The percentage of TSS during the first season in pomegranate fruits was low in the first phase and it gradually increased until the maximum when the fruits reached the maturity (165 DAFB). In the second season, the percentage of TSS has been gradually increased with some dips during fruit growth phases and then reached the highest value at maturity or just before it. However, Nab-El-Gamal cultivar contained the highest percentage of TSS at maturity.
The acidity in Nab-El-Gamal was high at 90 DAFB and then decreased gradually until it reached the lowest level at maturity. For Manfalouty and Hejazy, it began high and then it gradually decreased until it reached the lowest level at 135 DAFB and then it increased again or remains constant until the fruits reached their maturity.
Concerning TSS/acid ratio; Nab-El-Gamal cultivar recorded the highest ratio during the two seasons. In this cultivar, this ratio was low at 90 DAFB during the two seasons and then it began to gradually increase and reached the highest level at maturity while in Manfalouty and Hejazy it began low; increased and fell again until maturity. The current study revealed that - generally- the percentage of TSS in pomegranate fruits was low in the first phase and it gradually increased until the maximum when the fruits reached the maturity while the acidity was high and then decreased gradually until it reached the lowest level at maturity.
Concerning the sugar contents; both total and reducing sugars increased rapidly and reaching the highest percentage during maturation. The data revealed that the reducing sugars which are mainly consist of glucose and fructose is the predominant sugars in pomegranate juice while non - reducing sugars were found in a minor level. The present study revealed that total, reducing and non-reducing sugars increased progressively from the 1st phase (90 DAFB) until the fruit reached its maturity (165 DAFB) where they reached their maximum percentage.
3 - Antioxidant content:
Concerning the antioxidant contents of pomegranates; the study showed that in the first season, the Vitamin C (ascorbic acid) began more higher at the beginning of estimation, decreased at the middle of season (135 DAFB) and little increased again at the maturity. While in the second season in Nab-El-Gamal cultivar vitamin C (ascorbic acid) concentration increased progressively until the fruits reached their maturity, while in Manfalouty and Hejazy it increased until 135 DAFB and then decreased until the fruit reached the maturity. There were insignificant differences between the studied cultivars in both seasons of study. It was also observed that, vitamin C content was higher during the second season compared to the first one.
Total phenolic content (T.P.C.), Total anthocyanin content (T.A.C.) and Hydrolysable tannin content (H.T.C.) were determined in fruit peel and juice. Generally, the total phenolics content measured in the peel were higher than that found in the juice. The peel T.P.C. began high and gradually decreased, then reached the lowest level at maturity. The differences between the cultivars were significant in both seasons. The changes of total phenolics in the juice were differed between the cultivars. There were high significant differences between the three cultivars in this respect. During the two seasons; they started high, and then there was a gradual decline until they reached the lowest level at fruit maturity. The data also indicated that Hejazy pomegranate cultivar demonstrated the highest T.P.C in the juice followed by Manfalouty and then Nab-El-Gamal.
Total anthocyanin content (T.A.C.) of the three studied pomegranate cultivars was gradually increased in fruit peel upon fruit maturity where reached its maximum value. Hejazy cultivar had the highest level of T.A.C. with a significant difference between it and the two other cultivars in the first season and between it and Nab-El-Gamal in the second one. Additionally, Hejazy cultivar recorded the highest T.A.C. at fruit maturity. Total anthocyanin content of pomegranate juice began low for the three cultivars and gradually increased till the end of fruit growth. Manfalouty and Hejazy juice contained more T.A.C. than that found in Nab-El-Gamal. The differences were significant between both cultivars and Nab-El-Gamal.
Hydrolysable tannin content was measured as mg tannic acid/gm. of dry weight basis of peel and mg.∕ Lit. of juice. The peel contains much higher H.T.C. than that in the juice. In both seasons, H.T.C. in the peel began high and rapidly decreased reaching its lowest level at fruit maturity. The differences were significant between the studied cultivars in both seasons.
On the other hand, lower H.T.C. was found in the juice compared to peel. Similarly to the peel trend, H.T.C. declined rapidly upon fruit maturity where it reached the lowest values. There were insignificant differences between Manfalouty and Hejazy, however; the significant difference was found between them and Nab-El-Gamal cultivar.
Recommendation
The study showed that the pomegranate fruit contains large amount of antioxidants, which are the most important factor that led to the increase of Pomegranate fruit export in recent years. This is reflected the increase of cultivated areas of pomegranate, where the cultivated area increased from 5,000 feddans in the 1990s to nearly 30,000 feddans in the recent period.
The province of Assiut used to grow over 90% of the pomegranate trees; but at present Nubaria became the leader in this respect and planted with nearly adopted cultivars of pomegranates such as Wonderful are appropriate for the environmental conditions of this area Further action is needed in future researches to increase the fruit content of antioxidants and improve quality to increase competitiveness with countries exporting pomegranates.