高选择性的菜籽蛋白含量测定方法

Highly Selective Method for Rapeseed Protein Content Determination

为解决菜籽蛋白原料及制品中真蛋白含量难以测定的问题，建立了一种基于分级和定量2步完成的高选择性菜籽蛋白含量测定方法。通过酸化丙酮溶液和沸水萃取实施分级处理，可将样品中的非蛋白氮分离；结合应用可溶性蛋白的染色法测定和不溶性蛋白的凯氏定氮法测定，可获得样品的真蛋白含量。该方法变异系数不大于2．83％，回收率95％-96％，并可排除本源性非蛋白氮（包括芥子碱和硫甙）及外源性非蛋白氮（包括硝酸盐、铵盐、三聚氰胺和尿素）的干扰。该方法具备良好的抗干扰能力且不受蛋白质溶解性的影响，可推广到更多的植物蛋白制品及原料的真蛋白含量测定中，并可为相关行业的掺杂辨识或品质评价提供可靠手段。

To achieve reliable assessment on the true protein content in rapeseed protein materials or products, a highly selective determination method involving steps of sample fraction and protein quantification was established. Samples were extracted with acidified aqua acetone and subsequently with boiling water to remove the non - protein nitrogen （NPN） , and then the soluble protein in liquid fractions was determined by Bradford method while the insoluble protein in solid fraction was determined by Kjeldahl method, thus the combination of protein in both fractions, represents the true protein in sample. The method has shown desirable capability of anti - interference on both endogenous NPN （ including glucosinolates and sinapine） and exogenous NPN （ including nitrate, ammonium salt, melamine and urea）. In addition, the coefficient of variation was less than 2.83% and the recovery rate was within the range of 95%～96%. Due to the anti -interference capability on various NPN and compatibility on protein solubility, this method could be applied widely in determining various types of plant true protein and as reliable tool for adulteration identification or quality evaluation.