Influence of hot water treatment and O-carboxymethyl chitosan coating on postharvest quality and ripening in Hami melons (Cucumis melo var. saccharinus) under long-term simulated transport vibration.

Abstract

Hami melon (Cucumis melo var. saccharinus) is famous in China because of its delicious taste. The fast post-harvest metabolism of Hami melon, which is harvested in summer, creates challenges for preservation during storage. In this study, the ripening-related changes in Hami melon were monitored throughout postharvest storage, including transport. The effects of hot water (HW) treatment and HW treatment in combination with O-carboxymethyl chitosan (CMC) coating on ripening were evaluated based on the changes in membrane leakage; respiration rates; malondialdehyde (MDA) content; superoxide dismutase, catalase, and peroxidase activities; total antioxidant capacity (TAC); and total phenolic content during storage. Transmission electron microscopy and magnetic resonance imaging were also used to monitor changes in the quality of Hami melons during storage. The results indicate that transport vibration can accelerate ripening-related changes in Hami melon. Transport vibration increased membrane leakage and microstructural changes in the melon tissue; enhanced the respiration rate and MDA content; suppressed the activities of antioxidant enzymes; and decreased the TAC and total phenolic contents. Compared to HW treatment alone, HW treatment combined with the coating with 1% (w/v) CMC more effectively delayed the ripening-related changes in Hami melons under transport vibration. PRACTICAL APPLICATIONS: The results of this study show that transport vibration can accelerate ripening in Hami melons. Both hot water (HW) treatment and a combination of HW treatment and O-carboxymethyl chitosan (CMC) coating were effective in delaying ripening in Hami melons under simulated long-term transport vibration. Compared with HW treatment alone, HW treatment combined with CMC coating was more effective in preserving Hami melons, as indicated by lower respiration rates; better integrity of the plasma membrane and cell wall in the parenchyma tissue; lower membrane leakage and malondialdehyde content; greater antioxidant enzyme activities, total antioxidant capacity, and total phenolic content; and improved magnetic resonance imaging T2 relaxation values. Thus, HW treatment combined with CMC coating provides a useful way for the Hami melon industry to maintain postharvest quality, extend the shelf life, and improve the marketing of Hami melon.