Prestorage Heat Treatment as a Means of Improving Poststorage Quality of Apples

Additional index words. Malus domestics, color, firmness, acidity, soluble solids concentration, ethylene, respiration Abstract. The benefits conferred by a prestorage heat treatment on poststorage quality of apples (Malus domestics Borkh.) were measured on 'Anna', a non-storing early cultivar, and 'Granny Smith', a long-storing late cultivar. The major benefit was a decrease in rate of apple softening, both during OC storage and during simulated shelf life at 20C. Soluble solids concentration was not affected by heat treatment, but titratable acidity was reduced. Ethylene production after heat treatment and storage was similar to or higher than that of control apples, but respiration was lower. The optimum temperature and time combination for prestorage treatment of both cultivars was 4 days at 38C. High temperatures have been reported to inhibit ripening of many-fruits "(Mitchell, 1986). If held for too long above 35C, fruit will fail to ripen normally when returned to lower temper- atures. However, pears and apples have been reported to ripen normally if held at 40C for up to 6 days and then returned to 20C (Maxie et al., 1974; Liu, 1978). Liu examined ripeness indices of four cultivars of apples after 2 or 4 days at 40C and found that, compared to control, the heat treatment lowered titratable acidity, retained firmness, and had no effect on soluble solids concentration (SSC). Porritt and Lidster (1978) reported similar changes after storage of heat-treated apples. We have examined this prestorage treatment on 'Anna' apples, a non- scoring early cultivar, and 'Granny Smith,' a long-storing late cultivar. We determined how long the effects persisted in stored apples by examining their rate of ripening, ethylene production, and respiration after various durations of storage. We also de