初始pH值对果糖-赖氨酸模型美拉德产物抑制香蕉酶促褐变相关性质的影响

Effect of Initial pH in a Fructose-Lysine Model System on the Properties of Maillard Reaction Products Related to the Inhibitory Effect on Banana Enzymatic Browning

研究初始pH值对果糖-赖氨酸模型体系美拉德反应产物(MRPs)抑制香蕉酶促褐变相关性质的影响。通过调节初始pH值(2～11),于110℃条件下反应1h得到MRPs,对产物DPPH自由基清除能力、还原力、螯合Cu2+能力、抑制多酚氧化酶酶活能力进行考察。结果表明:碱性条件促使美拉德反应加剧,酸性条件MRPs能更有效抑制香蕉多酚氧化酶酶活力及清除DPPH自由基;pH9时的MRPs具有最好的还原力,而pH2时的MRPs具有最差的还原力;pH2～4和pH11条件下的MRPs具有较好的螯合Cu2+能力。总之,pH值对MRPs抑制香蕉酶促褐变有极大影响,不同初始pH值条件下的MRPs抑制香蕉酶促褐变的相关性质呈现较大差别,同时可以推测出具有抑制香蕉多酚氧化酶酶活力的组分可能是美拉德反应的初期产物。

This study focused on the effect of initial pH in a fructose-lysine model system on the properties of Maillard reaction products（MRPs） related to the inhibitory effect on banana enzymatic browning.MRPs were prepared through the reaction of 0.5 mol/L fructose and 0.5 mol/L lysine at a pH ranging from 2 to 11,110 ℃ for 1 h.Then,their antioxidant activity（including DPPH free radical scavenging ability and reducing power）,chelating copper activity and the inhibitory effect on polyphenoloxidase banana were evaluated.The results showed that the Maillard reaction between fructose and lysine could be accelerated at alkaline conditions,however,MRPs prepared from acidic conditions（especially at pH 2 or 3）,were more effective in inhibiting banana polyphenoloxidase and scavenging DPPH free radicals.The reducing power of MRPs prepared at pH 9 was highest,while those prepared at pH 2 had the lowest reducing power.Chelating copper activity of MRPs prepared at pH 2—4 or pH 11 was predominant.Generally,initial pH showed a significant effect on the efficacy of MRPs for inhibiting banana enzymatic browning,and the properties related to the inhibitory effect of MRPs prepared at different initial pHs were much different from each other,such as DPPH radical scavenging ability,reducing power,chelating copper activity and the inhibitory effect on banana polyphenoloxidase.It could also be deduced that early stage MRPs may play key roles in inhibiting banana polyphenoloxidase.