الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
The present study was conducted during the two seasons of 2019 and 2020 to determine the effects of some preharvest treatments i.e. thyme and oregano oils compared with control on grapes (Vitis vinifera) Flame seedless cv. physical and chemical properties during cold storage conditions. The obtained results could be summarized as follows: 5.1. Effect of preharvest applications of oregano and thyme essential oils on physical properties of 8Flame Seedless9 grapes during 45 days of cold storage Data confirmed that weight loss, grape berry decay, rachis browning score, gray mold decay, marketable percentage, berry firmness, visual appearance and grape berry shattering of grapes significantly affected by storage period, application treatments and their interaction in both seasons. 1. Storage periods effect The results showed that weight loss, grape berry decay, rachis browning score, gray mold decay and shattering of grape berry gradually increased with the extended cold storage period in both seasons where, the lowest weight loss, grape berry decay, rachis browning score, gray mold decay score and severity and shattering were recorded in the in the initial of cold storage period and then the three parameters increased step by step until reached their peak after 45 days of cold storage in both seasons. Data confirmed that, grape berry marketable, firmness and visual appearance gradually decreased with the extension of cold storage period where, the highest grape berry marketable percentages were recorded in the beginning 107 of cold storage period and gradually decreased until reached their lowest values after 45 days of cold storage both seasons. 2. Preharvest treatments effect The results showed that all preharvest treatments resulting large decrease in grape berry weight loss, decay and shattering and significantly increased grape berry marketable percentage, firmness and visual appearance over all cold storage periods compared with control in both seasons. Grape trees that treated with 2000 µL/L oregano oil preharvest showed the lowest grape bunches weight losses across all storage periods followed by thyme oil 2000 µL/L in both seasons. Treated grape bunches with 2000 µL/L oregano oil or thyme oil (2000 µL/L) 48 hours before harvest recorded the lowest bunches decay percentage, rachis browning score, gray mold decay score and severity and grape berry shattering and the highest marketable percentages, berry firmness and berry visual appearance in both seasons. 3. Effect of the interaction The results cleared that all preharvest application resulted in significantly decrease of grape berry weight losses, grape berry decay % and grape berry shattering and significantly delayed the reduction in grape berry marketable percentage, firmness, and visual appearance score in all cold storage periods in both seasons. Grape trees that treated with 2000 µL/L oregano oil as preharvest application had the lowest grape berry weight losses during all cold storage periods followed by thyme (2000 µL/L) in both seasons. 108 Grape bunches treated with 2000 µL/L oregano oil as preharvest application recorded the lowest grape berry decay percentages, rachis browning score, gray mold decay and grape berry shattering as well as the highest grape berry marketable percentages, berry firmness and grape berry visual appearance during all cold storage periods followed by thyme (2000 µL/L) in both seasons. 5.2. Effect of preharvest applications of oregano and thyme essential oils on physio-biochemical properties of 8Flame Seedless9 grapes during 45 days of cold storage The results confirmed that grape berry contents of anthocyanin, ascorbic acid, soluble solids content and titratable acidity as well as SSC/TA significantly affected by cold storage periods, preharvest treatments and their interactions in both seasons. 1. Storage periods effect The results cleared a gradually increase in grape berry contents of anthocyanin and total soluble solids in fruits as well as grape berry SSC/TA ratio with the extension of cold storage period, where the lowest berry contents of anthocyanin, and total soluble solids in fruits as well as grape berry SSC/TA ratio were recorded at the beginning of the storage period while, the highest grape berry contents of anthocyanin and total soluble solids in fruits as well as grape SSC/TA ratio were showed after 45 days of cold storage in both seasons. The results confirmed that grape berry content of ascorbic acid and titratable acidity gradually decreased with the increase of cold storage period in both seasons. The highest grape berry contents of ascorbic acid and titratable acidity were recorded in the beginning of cold storage period and the lowest 109 values were recorded at the end of cold storage period in the first and second seasons. 2. Preharvest treatments effect The obtained data cleared that grape berry contents of anthocyanin, ascorbic acid, SSC, and TA as well as SSC/TA ratio significantly differ under all preharvest treatments in both seasons. The highest content of anthocyanin was observed when grape berry treated preharvest with oregano or thyme oil 2000 µL/L in both seasons. The highest grape berry contents of ascorbic acid and TA as well as the lowest SSC/TA ratio were recorded under the preharvest application of oregano or thyme oil 2000 µL/L in both seasons. Bunches that treated preharvest with 2000 µL/L oregano or thyme oil recorded the lowest SSC in both seasons. 3. Effect of the interaction The obtained data indicated that all preharvest application significantly increased grape berry content of anthocyanin, ascorbic acid, and TA across all cold storage periods in both seasons. Also, all used treatments significantly decreased grape berry contents of SSC as well as SSC/TA ratio compared with control in both seasons. Grape berry that treated with oregano or thyme oil as postharvest application recorded the highest grape berry contents of anthocyanin after 45 days of cold storage in both seasons. 110 Grape berry that treated with 2000 µL/L oregano or thyme oil as preharvest application recorded the lowest grape berry contents of SSC in all cold storage periods in both seasons. Grape berry that treated with oregano or thyme oil at the rate of 2000 µL/L as preharvest application recorded the highest grape berry contents of ascorbic acid and TA as well as the lowest SSC/TA ratio in all cold storage periods in both seasons. 5.3. Effect of preharvest applications of oregano and thyme essential oils on enzymes activity of 8Flame Seedless9 grapes during 45 days of cold storage The results showed that peroxidase, polyphenol oxidase and pectin methyl esterase activities significantly affected by cold storage periods, pre-harvested treatments and interaction between preharvest treatments with storage periods in both seasons. 1. Storage periods effect The results confirmed a gradually increase in peroxidase, polyphenol oxidase and pectin methyl esterase activities with the extension of cold storage period. The lowest peroxidase, polyphenol oxidase and pectin methyl esterase activities were recorded in the beginning of the storage period while the highest peroxidase, polyphenol oxidase and pectin methyl esterase activities were detected after 45 days of cold storage in both seasons. 111 2. Preharvest treatments effect With respect to the effect of preharvest treatments the obtained data revealed that all used treatments resulting in a large decreased in peroxidase, polyphenol oxidase and pectin methyl esterase activities compared to control in both seasons. The lowest peroxidase, polyphenol oxidase and pectin methyl esterase activities were observed when grape bunches were treated preharvest with oregano or thyme oils at the rate of 2000 µL/L in both seasons. 3. Effect of the interaction The obtained data indicated that all preharvest application significantly decreased peroxidase, polyphenol oxidase and pectin methyl esterase activities across all cold storage periods in both seasons. Grape berry that treated with oregano or thyme oil at the rate of 2000 µL/L as preharvest application recorded the lowest peroxidase, polyphenol oxidase and pectin methyl esterase activities in all cold storage periods in both seasons. Conclusion The essential oils are considered eco-friendly and safe alternative to chemical compounds for the treatment of fruit. In this study, all applications of EOs, had a positive effect on maintaining grapes quality during storage. Based on this research, it can be concluded that preharvest treatments of 2000 and 4000 µL/L oregano and thyme EOs especially at low concentration of grape bunches cv. Flame Seedless before two days of picking date as alternative compounds to conventional use of sulfur dioxide during prolonged cold storage at 0°C can reduce various diseases especially gray mold caused by Botrytis cinerea and 112 reducing the deterioration of physical quality, including weight loss, rachis browning index and berry shattering percentage, marketable percentage, firmness and visual appearance score. In addition, retained berry contents of ascorbic acid and titratable acidity (TA) with slowing the increases in soluble solids content (SSC) and SSC/TA ratio. Moreover, inhibited the activities of peroxidase, polyphenol oxidase and pectin methylesterase enzymes during prolonged cold storage. Therefore, oregano and thyme EOs at 2000 µL/L treatments before two days of picking date may be used as alternative compounds to conventional use of sulfur dioxide to extend the storage life of processed grapes with an alleviating effect on physiological and chemical disorders.