The principle of melamine pseudoprotein

Due to the defects in the protein content testing methods of the food and feed industry, melamine is often used as a food additive by unscrupulous traders to improve the protein content index in food testing. Therefore, melamine is also known as “protein extract”.

Proteins are mainly composed of amino acids, and their nitrogen content generally does not exceed 30%, while melamine has a molecular formula nitrogen content of about 66%. The universal protein testing method Kjeldahl method estimates the protein content by measuring the nitrogen content. Therefore, adding melamine can make the protein test content of the food high, so that the inferior food can pass the test of the food inspection agency. It has been estimated that increasing the test protein content in plant protein powders and feeds by one percentage point, the cost of using melamine is only one-fifth that of real protein materials. As a white crystalline powder, melamine has no odor or taste and is not easily found after doping.

Milk powder incident: The protein content of each brand of milk powder is 15-20% (at night, the supermarket also saw 10-20% of the label on the packaging), and the average nitrogen content in protein is 16%. Calculated with a qualified milk protein content of 2.8%, the nitrogen content was 0.44%, and the content of a qualified milk powder protein was 18%. The nitrogen content was 2.88%. The melamine nitrogen content was 66.6%, which was 151 times that of milk and 23 times that of milk powder. Add 0.1 g of melamine per 100 g of milk to increase 0.4% protein.

Slightly soluble means that the solute 1g (ml) can be dissolved in the solvent from 100 to less than 1000ml, melamine is slightly soluble in water, and the solubility in the oil-in-water emulsion of milk does not find experimental data. I think the solubility is better than that of water. , to be verified.

Detection scheme

In the national standards for the detection of existing powdered milk, detection of proteins, fats, and bacteria is mainly performed. Melamine is a chemical raw material that is not allowed to be added to foods, so the existing standards will not include the corresponding content. That is, there is no national standard for melamine detection. Therefore, Rheinland TÜ V Group refers to the FCC melamine HPLC-UV quantification method, and can also use HPLC/MS detection method (laboratory method) for baby food, pet food, feed and raw materials ( Including starch, rice protein, corn protein, wheat bran powder, grain oil, etc.) Carry out the melamine test business, and the test results are authoritative.