Effect of nano zinc oxide coating on grape freshness and quality of its molasses

Abstract Grapes play a significant role as providers of phenolic, anthocyanin, and ascorbic acid, all of which are acknowledged for their considerable biological significance. The objective of this study was to investigate the possible utilization of nano zinc oxide coating for preserving the freshness of grapes and properties of its molasses. Nano zinc oxide suspension at three level of concentrations (0.0, 0.5, and 1.0% w/v) was carried out through a three-stage spraying process, which encompassed the flowering stage, the unripe stage, and the ripening stage, occurring 20 days prior to the harvest. Grape samples were stored at 4 ºC for 35 days. pH, titratable acidity, weight loss, Brixº, total phenolic, anthocyanin and ascorbic acid content, antioxidant activity, color indexes (L*, a*, b*), total viable count of bacteria, total yeast and mold count, and sensory analysis were evaluated at day 0, 7, 21, and 35. The pH, weight loss, Brixº, color index b*, total viable bacteria and total mold and yeast count of grape samples were increased over time. While titratable acidity, total phenolic, anthocyanin and ascorbic acid content, antioxidant activity, color indexes L*, a*, and sensory score were decreased. The results of this study suggested the use of 0.5% W/V of nano zinc oxide coating to enhance the grape freshness during storage.