QUALITY CHANGES IN HEAT TREATED SWEET ORANGE FRUIT DURING STORAGE AT LOW TEMPERATURE

The quality changes in heat treated sweet orange fruit during storage at low temperature were evaluated by subjecting sweet orange fruit to heat treatment for 0-20 minutes and storage at low temperature (5 +/- 1 degrees C) for 0-75 days. Low temperature storage for more than 30 days significantly increased the weight loss, surface pitting, disease incidence, TSS, TSS/Acid ratio. In contrast, acidity, reducing sugars and ascorbic acid declined during low temperature storage of sweet orange fruits, while non-reducing sugars were not affected significantly. Heat treatment, for 5-10 minutes at 50 degrees C, retarded the storage-associated changes in sweet orange fruit but longer heat treatments durations (15-20 minutes) declined the physical and chemical quality attributes. Ascorbic acid, however, continued to decrease even with modest heat treatment. The interaction of heat treatment and low temperature storage duration indicated no significant effect on weight loss, TSS, acidity, reducing sugars and ascorbic acid content but surface pitting, disease incidence and TSS/acid ratio increased significantly with 75 days storage at low temperature. While the maximum weight loss (8.83%) in control fruits after 75 days storage was at par with the heat treatment for 5-20 minutes. Disease incidence, after 75 days storage, was the highest (15.33%) with heat treatment for 20 followed by heat treatment for 15 minutes (10%) and control (8%) but was the least (5.33%) with heat treatment for 5 minutes which was at par with 10 minutes heat treatment.