Abstract
Effects of oxalic acid (OA) (10 and 20 mM) dipping on quality and antioxidant system of 'Hindi-Besennara' mangoes were studied during ripening for 8 days at 20 +/- 2 degrees C and 60-70% RH. Weight loss increased during ripening to 12.2% and was lower in OA treated fruit than control. Unmarketable fruit percentage (UFP) reached 6.7% in the control with no UFP in OA treated fruit after 5 days while, after 8 days, it was lower in treated fruit 19.1 and 13.3% at 10 and 20 mM OA, respectively than control (35.6%). OA treated fruit retained higher green color (a* values), firmness, titratable acidity (TA) and membrane stability index (MSI) but lower total soluble solids (TSS) and TSS/TA ratio during ripening especially after 3 and 5 days. Total phenol and flavonoid contents of fruit peel and pulp showed higher values during ripening than initial, fluctuated during ripening, and were higher in OA treated fruit especially at 20 mM than control. Vitamin C content was higher in OA treated fruit especially at 20 mM than control after 3 and 5 days. Radical scavenging capacity (RSC) of fruit pulp decreased (higher DPPH IC50 values) during ripening compared to initial and was higher in OA treated fruit than control after 8 days. While, RSC in peel was not changed during ripening and was higher in OA treated fruit than control. In both peel and pulp, polyphenoloxidase (PPO) activity gradually increased during ripening and was lower in OA treated fruit than control. While, peroxidase (POD) activity gradually increased during ripening and was higher in OA treated fruit than control. Polygalacturonase (PG), xylanase and a-amylase activities, in both peel and pulp, showed higher levels than initial, fluctuated during ripening and were lower in OA treated fruit than control. In conclusion, postharvest dipping in 20 mM OA retard ripening, retained and improved quality of 'Hindi-Besennara' mangoes during ripening via inhibiting hydrolytic enzymes and enhancing fruit antioxidant system.