Ellagic Acid Enhances Antioxidant System Activity and Maintains the Quality of Strawberry Fruit during Storage

Ellagic acid (EA) is a natural antioxidant, widely present in a lot of forms’ soft fruits, nuts, and other plant tissues, and helpful for promoting human health; however, its protective effect on postharvest fruit and improving the quality index of postharvest fruit have rarely been studied. In this experiment, the strawberries were soaked in 0, 100, 200, 300, 400, and 500 mg L⁻¹ EA, respectively, and the influential EA on fruit quality and the antioxidant system of strawberries were studied. Compared with the control, EA treatment can reduce the browning degree and rotting rate of strawberry fruit during storage and augment the soluble solid content (SSC). EA treatment can also increase the content of related stuff and enzyme activity in antioxidant systems; the gene expression level of polyphenol oxidase (PPO) in strawberries treated with EA was always down-regulated, correspondingly, the expression of other antioxidant enzyme genes was enhanced. Among the strawberry fruits treated with EA of different concentrations, 300 mg L⁻¹ EA had the best effect in the process of strawberry preservation. The results suggested that the proper concentration of exogenous EA at 300 mg L⁻¹ could maintain strawberries’ quality and enhance the antioxidant system by improving the activities of antioxidative enzymes and the ascorbate-glutathione (AsA-GSH) cycle during storage.