Method for analyzing protein adulteration in dairy products

Abstract

The invention discloses a method for analyzing protein adulteration in dairy products. The method comprises the following steps of: dividing a sample into two parts, performing alkaline hydrolysis on one part of the sample, and performing acidolysis on the other part of the sample; neutralizing by using acid after alkaline hydrolysis, drying by distillation after acidolysis, redissolving by using dilute acid, derivatizing the redissolved liquid by using derivating agents, and filtering by using an organic filter membrane so as to obtain sample liquor; respectively preparing a tryptophan standard solution and a mixed standard solution of threonine, valine and lysine; and respectively injecting the standard solutions and the sample liquor into a high performance liquid chromatograph, then measuring the peak area of the standard solutions and the peak area of the sample liquor, and calculating the content of the tryptophan, the threonine, the valine and the lysine in the sample liquor. The method is simple in operation, low in analysis cost and easy to popularize and apply, and an analysis result can be obtained quickly.

Description

technical field [0001] The invention belongs to the technical field of liquid chromatography analysis, and in particular relates to an analysis method for protein adulteration in dairy products. Background technique [0002] With the improvement of living standards, people's demand for milk and dairy products shows a continuous upward trend. Driven by huge market interests, many dairy production companies or individuals adulterate dairy products in order to make huge profits. Milk is rich in protein, fat, and carbohydrates. According to the nutrition required by human beings, protein is the ingredient with the highest nutritional value in milk. Therefore, one of the main indicators for the detection of milk and dairy products is protein; correspondingly, milk The adulteration of products is mainly aimed at the adulteration of milk protein. For example, in Shandong in 2005, it was found that milk had been added with leather hydrolyzed protein; in 2008, Shijiazhuang Sanlu G...

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Problems solved by technology

[0003] Monitoring is an important management measure to ensure food safety in the market, and it is also a routine work of the Chinese government management department. However, there are currently the following problems in the monitoring of milk protein adulteration: 1. There are loopholes in the detection method: the protein content determination method in milk / milk powder is Kjeldahl method, this method converts nitrogen content into protein for quantification, as long as various compounds with high nitrogen content are added, similar adulteration effects can be produced, so it is necessary to fundamentally solve the adulteration of milk / milk powder The problem needs to be solved from the means of protein determination; 2. Protein is composed of amino acids. In theory, detecting the content and ratio of all essential amino acids can achieve the control of protein adulteration. At present, the simultaneous detection of all essential amino acids is generally used. Amino acid analyzers, the detection cost is quite high, it is difficult for grassroots detection departments to have such detection resources

[0004] The existing detection of protein adulteration in dairy products, one is the detection of adulteration of non-protein nitrogenous substances. At present, the research on this is relatively mature at home and abroad, and there are existing international standards to strictly monitor it; the other is The detection of non-dairy protein adulteration is currently mainly based on the differences in protein amino acid composition, solubility, antigen specificity, molecular weight, and charge, but most of the operations are cumbersome and time-consuming. There is no report on the identification of milk protein adulteration by amino acid pattern

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