Effects of packaging materials on the quality and non-enzymatic browning of litchi juice during storage

Quality changes and non-enzymatic browning of litchi juice during storage away from light at 25℃ in the PET bottles,PLA bottles and PET/Al/PE laminated film bags were investigated.Partial least squares regression(PLSR) method was used to analyze the influence of packaging materials on the non-enzymatic browning of litchi juice.The results showed that a faster degradation of L-ascorbic acid(L-AA) happened when litchi juice was stored in the PLA bottles compared with that in the PET bottles and laminated film bags. At the beginning of storage, the dissolved oxygen concentration (DOC) decreased sharply for all the packages.As the storage time proceeded,DOC dropped gradually and finally leveled off,except for the PLA bottles in which DOC increased fast. Barrier properties of packaging material have significant effects (p<0.05) on L-AA concentration and DOC.Sucrose in the juice hydrolyzed constantly during storage,while the concentration of both fructose and glucose displayed a fast increase at the beginning of storage and then decreased slowly.The total amount of amino acids and phenol decreased continuously.The Total Soluble Solid(TSS) increased slowly,while the pH value showed a slow decrease.The content of 5-HMF and Browning Index (BI) increased continuously. The barrier properties of the packing materials caused different DOC in the litchi juice,and the dissolved oxygen led to the degradation of L-AA and oxidative polymerization of phenolic substances,which finally resulted in the non-enzymatic browning of the litchi juice.