利用电子自旋共振技术研究美拉德反应自由基变化

摘要

为寻求简便而准确地对食品加工和贮藏过程中的美拉德反应进行鉴定的方法,该文研究加热食品中葡萄糖和乳球蛋白建立的美拉德反应体系的自由基变化,主要考察影响美拉德反应的温度和 pH 值变化导致的自由基改变,从而确定美拉德反应与其自由基变化之间的相互关系。在3种不同温度、有无氧气和3种不同pH值条件下,利用电子自旋共振(electron spin resonance,ESR)光谱检测美拉德反应自由基变化趋势,结果随温度升高,自由基数量增加,反应速度加快；随 pH 值由酸性向碱性移动,自由基数量增加；自由基数量在无氧条件时多于有氧条件。当自由基积累到一定浓度,由于聚合反应生成高分子聚合物使信号强度下降,最后消失。比较美拉德产物与2种底物产生的自由基发现,无论类型、数量还是生成速率都存在明显差异。研究结果表明,采用自旋捕集剂对不稳定的自由基进行捕集来分析信号能够有效表征加热食品中美拉德反应初中期阶段的自由基变化,从而有效表征和分析美拉德反应过程。与传统研究美拉德反应的分析方法比较,ESR光谱是一种简便灵敏的分析方法,可以作为研究加热食品美拉德反应的重要方法之一。%Electron spin resonance (ESR) spectroscopy was used to study the change of free radicals generated by the Maillard reaction of glucose and β-Lactoglobulin in the food-heating process, especially the change of free radicals caused by the changes of the temperature and pH. The relationship between Maillard reaction and the radicals in Maillard reaction can be determined by analyzing the change of the radicals in order to establish a simple and accurate method to evaluate Maillard reaction. Under the conditions of four different temperatures, three pH levels and with or without oxygen, the radical change trend of Maillard reaction was investigated that the radicals increased from 1.7×104 to 2.4×104 and the max reaction speed appeared from 90 min to 5min with temperature rise from 50-80℃. The radicals increased from 5×103 to 2.4×104 and the reaction sped up with pH rise from 5.0 to 8.0. The radical’s amount raised and the radical signal intensity were higher under anaerobic conditions with pH increasing. When radicals were accumulated to a certain concentration, the signal strength dropped and finally disappeared due to its own collision or polymerization. Compared with the radicals of two types of substrates, the radicals of products of the Maillard reaction in type, quantity and rate of formation. It is proved that the stable signal of radicals obtained by the spin trapping can effectively present the reaction trend of radicals in the early and middle stages in the Maillard reaction of food heating, and it is easy to reflect the change of Maillard reaction. Compared with the traditional detection methods of the Maillard reaction, ESR spectroscopy is a simple and sensitive method of radical detection, and can be used as an important research method of Maillard reaction for food heating.