Effect of Protocatechuic Acid-Grafted-Chitosan Coating on the Postharvest Quality of Pleurotus eryngii

Protocatechuic acid-grafted-chitosan (PA-g-CS) solution with antioxidant activity was developed as a novel edible coating material for Pleurotus eryngii postharvest storage. The effect of PA-g-CS coating on the postharvest quality of P. eryngii was investigated by determination of various physicochemical parameters and enzyme activities. Results showed that the antioxidant capacity and viscosity of PA-g-CS solutions were closely related to the grafting degree and were much higher than that of chitosan (CS) solution. At the end of 15 days of storage, serious mushroom browning was observed in the control and CS coating groups. By contrast, PA-g-CS coating groups with medium and high grafting degrees maintained better physical appearance. Among all of the treatment groups, P. eryngii in PA-g-CS III coating group exhibited the highest firmness and the lowest weight loss, browning degree, respiration rate, malondialdehyde content, electrolyte leakage rate, superoxide anion production rate, and hydrogen peroxide content. Moreover, P. eryngii in PA-g-CS III coating group maintained relatively higher antioxidant enzyme activities but lower polyphenol oxidase activity than other treatment groups. Therefore, PA-g-CS III is a promising preservation agent for P. eryngii.