An approach to the detection of synthetic milk in dairy milk: 1. Detection of urea

A qualitative test for the detection of externally added urea (as synthetic milk) was developed using soybean urease. The quantitative detection of synthetic milk in dairy milk could be achieved by this method based on the 'a' value of 'L, a, b' scale of the HunterLab colorimeter and also by the diacetyl complexation method. Both methods are sensitive enough to detect amounts as low as 2% synthetic milk added to dairy milk, corresponding to 20 mg of added urea per 100 ml.
This work reports on methods to detect and estimate unionic detergents, which are important ingredients of synthetic milk formulations, based on the extraction of a detergent—Methylcne Blue complex in chloroform which can be subsequently quantified by measuring the optical density at 653 nm. A base value of 0.52 for optical density was found to represent pure cow's milk Any result above this value suggested the presence of an anionic detergeni in milk.