TEXTURE MODIFICATION OF PROCESSED APPLE SLICES BY A POSTHARVEST HEAT TREATMENT

Exposure of Spartan apples (Malus pumila Mill) to 38°C for 6 days immediately after harvest resulted in a significant reduction in softening during 4 months cold storage. The heat treatment significantly depressed titratable acidity but did not affect soluble solids levels. After 6 months cold storage the apples were prepared as thermally processed slices in retort pouches which were stored at 37° C for 16 wk before product quality was evaluated. Both shear force determinations and sensory analysis revealed that the postharvest heat treatment resulted in significantly firmer apple slices. Calcium dipping as a preprocess treatment also significantly increased apple firmness but control apple slices with calcium added were only as firm as heat-treated slices without added calcium. Color of the processed slices was slightly affected by the heat treatment but the flavor was not. The sensory panelists significantly preferred the 38°C postharvest heat-treated processed apple slices overall.