黑龙江市售乳制品蛋白质质量评价

Evaluation of Protein Quality of Commercially Available Milk Products in Heilongjiang

为评价黑龙江省市售乳制品中蛋白质的质量,采用凯氏定氮法和三氯乙酸沉淀法测定黑龙江市售不同厂家生产的全脂加糖乳粉、纯酸牛乳、配制型乳饮料和灭菌纯牛乳中的蛋白质和非蛋白氮含量,计算各乳制品的蛋白氮指数和非蛋白氮指数。结果表明,利用蛋白氮指数和非蛋白氮指数评价乳制品中蛋白质质量是可行的,并建立了4种乳制品的蛋白氮指数和非蛋白氮指数模型。黑龙江市售合格的全脂加糖乳粉、纯酸牛乳、配制型乳饮料和灭菌纯牛乳的蛋白氮指数范围分别为0.990～0.995、0.870～0.956、0.402～0.633和0.929～0.943,其非蛋白氮指数范围分别为0.005～0.010、0.084～0.130、0.367～0.598和0.069～0.071。总体来说,黑龙江市售乳制品蛋白质含量大多数符合国家标准规定,但部分乳制品的蛋白质质量有待提高。

In order to evaluate the protein quality of milk products commercially available in Heilongjiang,protein and non-protein nitrogen contents in sweetened whole milk powder,yoghurt,milk beverage,and sterilized pure milk were determined by micro-Kjeldahl method and trichloroacetic acid precipitation method,respectively,and protein and non-protein nitrogen indexes were calculated.The results showed that it was feasible to evaluate protein quality of milk products based on protein and non-protein nitrogen indexes.Four models for protein and non-protein nitrogen indexes in milk products were established.The protein nitrogen indexes of certified sweetened whole milk powder,yoghurt,milk beverage,and sterilized pure milk were in the range of 0.990 to 0.995,0.870 to 0.956,0.402 to 0.633,and 0.929 to 0.943,and the non-protein nitrogen indexes were in the range of 0.005 to 0.010,0.084 to 0.130,0.367 to 0.598,and 0.069 to 0.071,respectively.On the whole,protein content of commercially available milk products in Heilongjiang is generally consistent with the national standard,although part of them needs to be improved due to poor protein quality.