Effect of heat treatment on polyphenol oxidase activities and quality attributes and shelf life of table grape

The effect of heat treatment on shelf life and quality attributes of table grape (Vitis vinifera cv.bidaneh Sefid) during storage was studied. Table grapes were treated with hot water (22 °C as a control, 45, 50 and 55°C) for 1 min and stored at 1±0.5°C with 90-95% RH for 30 days (p<0.05). Fruit quality attributes including weight loss, marketability, pH, total soluble solids (TSS), total phenolics content and polyphenol oxidase activities were studied during cold storage at 15 day intervals. Postharvest treatment of fruit with hot water of 55°C retained fruit quality during storage. Hot water of 55°C retained berry weight, marketability and phenolics content and decreased the rate of increase in pH and polyphenol oxidase activity in grape samples. The results showed that heat treatment as an appropriate nonchemical method can improve the quality and shelf life of table grapes.