Effects of temperature and SO2 addition on quality and postharvest behavior of mechanically-harvested juice grapes in Arkansas

Abstract

Temperature of fruit of Vitis labrusca L. cv. Concord at harvest was the primary factor governing the rate of postharvest quality changes. Fruit harvested at mid-day at 32°C remained at that temperature inside a bulk pallet box for 72 hours, regardless of diurnal temperature fluctuations. Without addition of SO2, alcohol concentration steadily increased after 12 hours holding the mechanically-harvested grapes in a bulk pallet box and reached 3% after 72 hours. Loss of soluble solids began immediately after harvest and after 72 hours, 44% of the soluble solids present at the time of harvest had been lost. Addition of SO2 at harvest or no later than 6 hours after harvest aided in slowing postharvest deterioration. The addition of 80 or 160 ppm SO2 to a bulk pallet box of grapes mechanically harvested at a temperature of 35° was as effective in retarding postharvest deterioration of the quality attributes determined in this study as was harvesting at 24°. Harvesting at a cool temperature (24°) and SO2 addition will allow for extended holding of the raw product with minimal alcohol production and raw product quality loss.