Effects of Polyacrylamide Resin on Pericarp Browning and Diseases of Litchi Fruits During Low Temperature Storage

【Objective】The purpose of this study was to investigate the effect of humidity control on pericarp browning and fruit disease development during low-temperature storage with modified-atmosphere packaging of litchi.【Method】With polyacrylamide（PAM）resin as a humidity regulator, PAM（10 g PAM for 1 kg litchi fruit）was added in polyethylene（PE）film packaging bag with Huaizhi fruit, and the disease index, decay rate and other physiological and biochemical changes of litchi during storage were studied.【Result】Compared with the control treatment, the application of PAM resin in PE film packaging bag could effectively reduce the relative humidity in the litchi package during storage at 5℃ , with the fluctuation range of 80%-90%. After 28 days of storage, the decay rate and the disease index of the control fruits were 31% and 2%, respectively while those of the litchi treated with PAM were 11% and 1.2%. PAM treatment inhibited the development of diseases significantly.However, The pericarp browning and loss of fresh weight of fruits treated with PAM were slightly higher than those of the control, while the water content in fruit and anthocyanin content in the pericarp were slightly lower than those of control.【Conclusion】PAM treatment significantly inhibited the disease index and fruit decay during lowtemperature storage with modified-atmosphere packaging, and had little effect on pericarp browning. Application of appropriate amount of humidity regulator and combining with the appropriate thickness film could be a promising strategy to solve the contradiction between fruit decay and pericarp browning during postharvest storage and transportation of litchi fruits.