Combination effects of preharvest tree net-shading and postharvest fruit treatments with salicylic acid or hot water on attributes of pomegranate fruit

Abstract

Aril whitening (AW) or aril paleness is a physiological disorder in pomegranate fruit that occurs during fruit growth and developmental stages in main production areas in Iran, resulting to decrease in fruit quality. The aim of this study was to investigate the influence of preharvest green net shading and postharvest treatments of salicylic acid (SA) or hot water (HW) on fruit quality parameters and bioactive compounds of pomegranate cv. Ghojagh at harvest and during storage. This experiment was carried out on fruit of nine-year-old pomegranate trees growing under open field as control and trees covered under green 50% net shading for duration of about 4 months (June until the September, warmest months of the growth season). The fruits were harvested at the commercial stage and transferred to the laboratory, where subsequently treated by immersing in hot water (45 ºC) for 4 min or 2 mM SA at room temperature (2 min). As control postharvest treatment, a part of fruits were treated only with water for 4 min at room temperature. The fruits were then air-dried and transferred into a refrigerated storage at 4 ± 1 ºC, 80 ± 5% RH for a period of 90 days. A significant reduction in aril whitening, as well as fruit sunburn and cracking was observed from trees under 50%-green net shading in comparison with the control non-shading trees. Fruits of net shading had significantly higher bioactive compounds (ascorbic acid, phenolics and anthocyanin, antioxidant activity), less weight loss and lower chilling injury than the non-shading fruits during storage. Also, postharvest treatments, especially SA, had a good impact on reducing chilling injury and retaining the quality and nutritional value of pomegranate fruits.