贮藏过程中溶解氧对荔枝汁非酶褐变的影响

本文研究了荔枝汁在不同初始溶解氧浓度及有顶空氧存在的贮藏条件下的非酶褐变情况,采用PLSR进行分析揭示不同溶解氧浓度对荔枝汁非酶褐变的影响规律。结果表明:在0~3 d的贮藏期内,随着DOC的快速下降,低溶解氧和中溶解氧荔枝汁的L-AA进行有氧降解;在3 d~17 w的贮藏期内,DOC下降缓慢,趋于稳定,L-AA进行有氧降解和无氧降解,并以无氧降解为主。随着贮藏前期DOC和顶空氧浓度的快速下降,高溶解氧荔枝汁的L-AA持续进行有氧降解并在第4 w时基本全部降解完毕。三种溶解氧浓度的荔枝汁中的蔗糖均不断降解,但果糖和葡萄糖含量呈现先快速增加后减少的趋势。5-HMF和褐变指数不断地增加,溶解氧浓度越高,增加的越快。表儿茶素不断的降解,而芦丁含量比较稳定。在不同溶解氧浓度下,荔枝汁的非酶褐变是以L-AA降解及酚类物质氧化聚合为主,美拉德反应为辅。

Effects of Dissolved Oxygen on Non-Enzymatic Browning of Litchi Juice during the Storage

The non-enzymatic browning of litchi juice during storage was investigated under the storage conditions of different initial dissolved oxygen concentrations (DOC) and headspace oxygen. The effects of DOC ion non-enzymatic browning of litchi juice was analyzed by PLSR. Results showed that the changes of L-AA of litchi juice were dominated by aerobic degradation in low and medium DOC with the rapid decrease of DOC during the storage of 0~3d. The DOC decreased slowly and tended to be stable during the storage of 3 d~17 w, and the changes of L-AA were both dominated by aerobic degradation and anaerobic degradation, and mainly by anaerobic degradation. The L-AA of litchi juice in high DOC continued aerobic degradation and almost completely degraded in 4 w with the rapid decrease of DOC and headspace oxygen concentration during the pre-storage. The sucrose of litchi juice degraded constantly under the condition of three DOC whereas the content of fructose and glucose exhibited a trend of rapid increase and then decrease. The 5-HMF and BI increased constantly with the increase of DOC. Epicatechin degraded continuously whereas the content of rutin was relatively stable. The non-enzymatic browning of litchi juice was dominated by L-AA degradation and oxidative polymerization of phenolics with Maillard reaction supplemented in different DOC.