The Effects of Poly-γ-Glutamic Acid on the Postharvest Physiology and Quality of Strawberry cv. Hongyan during Cold Storage

This study investigated the effects of poly-γ-glutamic acid (γ-PGA) on the postharvest physiology and quality of the strawberry cv. Hongyan during cold storage. The results showed that all concentrations of γ-PGA improved decay control and strawberry preservation by enhancing antioxidant capacity, delaying the softening process, and maintaining fruit quality, especially for 100 mg·L−1 γ-PGA. After 14 days of treatment, compared with control, 100 mg·L−1 γ-PGA decreased weight loss, decay rate, and index by 21.9%, 75.0%, and 66.7% and increased the total antioxidant capacity by 43.5% through antioxidant enzymes. In addition, 100 mg·L−1 γ-PGA increased fruit firmness by 53.6% by decreasing the activities of polygalacturonase, pectin lyase, cellulase, and β-galactosidase. In terms of color quality, 100 mg·L−1 γ-PGA improved the values of lightness and yellowness by 30.9% and 52.8%. As regards nutritional quality, 100 mg·L−1 γ-PGA increased the contents of protein, soluble sugars, vitamin C, and total phenols by 106.6%, 80.6%, 51.2%, and 78.4%. In terms of sensory quality, 100 mg·L−1 γ-PGA increased the soluble solids’ content by 19.0% and decreased the titrated acids’ content by 21.1%, which increased the sugar–acid ratio by 50.9%. Our findings suggest that 100 mg·L−1 γ-PGA can be used to improve the decay control and preservation of strawberry cv. Hongyan under cold storage.