EFFECTS OF POSTHARVEST HOT WATER TREATMENT ON PHYSIOLOGICAL AND BIOCHEMICAL PROPERTIES OF 'EKSOTIKA' PAPAYA DURING RIPENING

Abstract

Effects of postharvest hot water treatment (HWT) on the 'Eksotika' papaya fruit quality during ripening were investigated. HWT is a method for fruit fly disinfestation which is a quarantine requirement for the papaya exportation industries. Fruit were harvested at maturity stage Index 2 (green with a tinge of yellow). One group was treated with hot water at 47±1°C for 10 min and another group was untreated. Fruit were left to ripen at ambient temperature (25°C) and were taken into experiment at Index 2 (Harvest Index), Index 4 and Index 5. Physiological changes including peel colour, weight loss, fruit firmness, total soluble solids (TSS) and pH were determined at the three different ripening indices. Biochemical changes including total sugars and total reducing sugars were also investigated. From the results, both treated and untreated fruit showed normal ripening. There were also no significant differences in weight loss, TSS and pH value between the untreated and treated fruit at the three ripening indices. However, the peel colour changes in untreated fruit were delayed by approximately 1-2 days. At Index 5, the treated fruit was firmer than the untreated fruit. The total sugars and total reducing sugars contents showed no significant difference between the two groups at the three different ripening indices. The reducing sugar content was increased and attained highest value at Index 4. Conversely, the non reducing sugar content was decreased during ripening. Although HWT hastened degreening (of peel), cause slightly firmer fruit when ripe, fruit sweetness was remained unchanged and maintained at a good quality. This suggests that postharvest hot water treatment at the selected temperature can maintain postharvest quality of 'Eksotika' papaya fruit and at the same time prevent it from insect infestation.