Effect of chitosan coatings with putrescine on the postharvest quality of oranges during storage at chilling temperatures

The application of edible coatings (EC) is an important area of postharvest research aimed at controlling the ripening and senescence of fruit and vegetables. Citrus fruits are among the most important crops worldwide; however, their quality deteriorates during postharvest and they are susceptible to developing chilling injury (CI) when stored at 2 °C. At present, the combination of chitosan (CTS) with putrescine (PUT) has not been evaluated as an alternative strategy to delay quality losses in ‘Valencia Late’ oranges during 90 days of storage at 2 °C followed by 2 days at 21 °C. Specifically, the effect of postharvest application of different EC based on 1% CTS and PUT at two concentrations (0.1 and 5 mM) was assessed on weight loss, respiration rate, ethylene production, physicochemical quality, CI incidence, and total phenolic content in both peel and juice. The results showed that the EC containing CTS + PUT 0.1 mM significantly delayed weight loss and fruit softening from 30 and 60 days of storage, respectively. In addition, this coating significantly reduced respiration rate, ethylene production, and CI incidence. At a functional level, oranges treated with CTS + PUT 0.1 mM exhibited significantly higher total phenolic content in both peel and pulp compared with the other treatments evaluated. Furthermore, all coatings based on CTS and PUT delayed colour loss after 90 days of storage compared with the control. Total soluble solids content was significantly lower in treated oranges compared with the controls, although total acidity was significantly increased by these treatments. However, oranges treated with CTS + PUT 5 mM showed the greatest weight loss, as well as a significant increase in respiration rate and CI incidence scale. In conclusion, the CTS + PUT 0.1 mM coating could be an effective postharvest tool to delay quality losses in oranges during cold storage.