非硫无毒的抗褐变抑制剂的筛选是目前的研究热点。前期研究显示果糖-赖氨酸模型体系美拉德反应产物对香蕉酶促褐变具有明显的抑制效果。本文研究了分级对该体系产物抑制香蕉酶促褐变相关性质的影响。首先通过超滤、透析等方法将美拉德产物分级为MW<3500 u、MW>5000 u及3500 u5000 u级分的螯合铜离子能力最好，MW<3500 u级分次之。MW<3500 u级分的DPPH?清除能力和抑制香蕉多酚氧化酶能力更佳，分别达46.13%、0.089 mg/mL（IC50）。三种级分对游离酶和酶-底物络合物的抑制常数分别为：KI=0.297 mmol/L，KIS=1.744 mmol/L（MW>5000 u）；KI=0.212 mmol/L，KIS=1.656 mmol/L（3500~5000 u）；KI=0.205 mmol/L，KIS=1.536 mmol/L（MW<3500 u）。说明MW<3500 u级分与游离酶及酶-底物络合物结合更紧密。综上，MW<3500 u的MRPs具有最优的抑制香蕉酶促褐变的能力。

Screening of non-toxic and non-sulfur anti-browning inhibitors is a hot topic. Maillard reaction products (MRPs) in fructose-lysine model system exhibited strong inhibitory effect on banana enzymatic browning in our previous study. The study mainly discussed the effect of fractionation of the products on the inhibition propertie. Ultrafiltration and dialysis were applied to divide the MRPs into three grades: MW >5000 u fraction, MW < 3500 u fraction and 3500 u < MW < 5000 u fraction. The antioxidant activities (including DPPH?scavenging ability and reducing power), chelating copper activity and the inhibitory effect on banana polyphenol oxidase were evaluated. The fraction with MW >5000 u showed the best chelating copper ion ability, followed by that with MW < 3500u. The fraction with MW <3500 u exhibited the best DPPH?scavenging ability (46.13%) and polyphenol oxidase inhibitory ability (IC50 0.089 mg/mL). Free enzyme inhibition constant (KI) and enzyme-substrate complex inhibition constant (KIs) of the obove-mentioned three parts were KI=0.297 mmol/L and KIS=1.744 mmol/L (MW >5000 u), KI =0.212 mmol/L and KIS=1.656 mmol/L (5000 u > MW >3500 u), KI =0.205 mmol/L and KIS=1.536 mmol/L (MW <3500 u). The fraction with MW <3500 u could combine free enzyme and enzyme-substrate more tightly. In conclusion, the fraction with MW <3500 u was shown to be the best for inhibiting banana enzymatic browning.

国家自然科学基金项目(31101328)；海南省自然科学基金项目(311063)