Effect of Postharvest Citric Acid Treatment on Controlling Blue Mould and Preserving the Quality of Apple Fruits during Storage

Apple(cv. Qingguan) fruits which had been wounded and artificially inoculated with Penicillium expansum were subjected to dipping treatments with different concentrations of citric acid and subsequent storage at room temperature in order to investigate the inhibition of lesion development and the preservation of apple fruit by citric acid treatment. In vitrotest indicated that citric acid inhibited spore germination of P. expansum, and 1% citric acid showed the highest inhibitory rate. In vivo test indicated that 1% citric acid was the optimal concentration for controlling blue mould of apple fruits. Postharvest citric acid treatment significantly increased the activities of peroxidase(POD), catalase(CAT) and ascorbate peroxidase(APX), delayed the increase in weight loss and the decreases in hardness and the contents of titratable acid, ascorbic acid and soluble solid, and postponed the respiration peak in apple fruits.