Effect of γ-PGA Coating on Storage Quality and Respiratory Metabolism of Postharvest ‘Golden Younai’ Plum Fruit

In order to study the control effect of γ-polyglutamic acid (γ-PGA) coating treatment on the storage quality of postharvest ‘Golden Younai’ plum fruit and its relationship with respiration metabolism, 4 g/L γ-PGA was used to treat the postharvest ‘Golden Younai’ plum fruit, to evaluate the changes in fruit quality indicators and respiration rate during cold storage, and to further study the changes in important intermediate metabolites and key enzyme activities of the fruit respiration metabolism glycolysis-tricarboxylic acid cycle pathway. The results showed that the γ-PGA treatment delayed the decrease of the firmness of fruit during the early storage period, increased and maintained the soluble solid content during the storage period, slowed the increase in the weight loss rate and the decrease in the good fruit rate, and inhibited the respiratory intensity; further research found that, γ-PGA treatment inhibited the activity of hexokinase in the glycolysis of fruit, maintained the activities of phosphofructokinase and pyruvate kinase, delayed the decrease of glucose and pyruvate content, and also promoted the decrease of α-ketoglutarate dehydrogenase, succinate dehydrogenase activity and succinic acid content, while maintaining high citrate synthase activity, slowing down the decrease of citric acid and malic acid content. Therefore, 4 g/L γ-PGA coating treatment can reduce the loss of the respiratory substrates and intermediates via affecting the EMP-TCA pathway, which contributed to less material consumption during the storage, maintaining the quality and prolonging the shelf-life of harvested ‘Golden Younai’ plum fruit.