The composite film of thyme essential oil and EGCG delays the decline of quality in blueberries by regulating reactive oxygen species.

In this study, a composite film embedded with thyme essential oil and gall catechin gall ester (EGCG) was prepared to extend the shelf life of the fruit. Blueberries were adopted as the experimental object to assess the efficiency of this composite film treatment in alleviating quality degradation during storage. The results showed that composite film treatment inhibited the decline of fruit firmness, reduced weight loss, and preserved the levels of soluble solids, titratable acids, total phenols, anthocyanins and flavonoids. In addition, this treatment also inhibited the generation rate of superoxide anions and the accumulation of H2O2. Correlation analysis revealed a close association between reactive oxygen species (ROS) and quality deterioration. Composite film treatment reduced the production of ROS in blueberries by enhancing the activity of key reactive oxygen species scavenging enzymes, including superoxide dismutase (SOD), hydroperoxidase (CAT), peroxidase (POD) and ascorbic acid peroxidase (APX). This helped to maintain the firmness and nutritional level of blueberries, delayed the deterioration of quality, and prolonged the postharvest shelf life of blueberries at room temperature. Moreover, the application of this composite film offered novel perspectives for the development of safe and non-toxic preservation technologies in subsequent studies.