包装材料对贮藏期荔枝汁品质及非酶褐变的影响

研究了聚酯(PET)瓶、聚乳酸(PLA)瓶和聚酯/铝箔/聚乙烯(PET/Al/PE)复合袋装荔枝汁在25℃避光贮藏时的品质变化和非酶褐变情况,采用偏最小二乘法回归(PLSR)分析包装材料对荔枝汁非酶褐变的影响。结果表明:贮藏过程,PLA瓶装荔枝汁的L-抗坏血酸(L-AA)发生快速降解,PET瓶和复合袋中的L-AA降解缓慢;贮藏初期,溶解氧浓度(DOC)均急剧下降,贮藏后期,除PLA瓶中的DOC快速上升外,其它包装材料中的DOC均平缓下降并趋于稳定。包装材料阻隔性能对L-AA含量和DOC有显著(p<0.05)影响。蔗糖不断水解,果糖和葡萄糖含量在贮藏初期快速地增加,然后缓慢下降。氨基酸总量和总酚含量不断下降。可溶性固形物(TSS)含量缓慢上升,pH缓慢下降。5-HMF含量和褐变指数不断上升。包装材料阻隔性能使得荔枝汁中的溶解氧浓度差异,溶解氧能引起L-AA的降解和酚类物质氧化聚合,导致荔枝汁发生非酶褐变。

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.