Identification of urea in raw milk by infrared spectrometry

Abstract

The introduction of urea (carbamide) into the composition of raw cow's milk artificially increases the protein level, which is a key parameter for evaluating product quality. However, traditional methods of analysis based on the measurement of nitrogenous compounds do not allow to distinguish natural protein from added urea, which creates a risk of falsification. To detect urea, the colorimetric method is used, regulated by GOST R 55282-2012, and according to GOST R 52054-2023, the maximum urea content in milk is established. Despite its accuracy, this technique requires significant time and labor costs. The research was conducted in stages on the basis of the Educational and Research Center for Food and Animal Feed Expertise of the St. Petersburg State University of Veterinary Medicine. Samples of raw milk without urea and with its addition in various concentrations, as well as a standardized urea sample, were used as objects of analysis. At the first stages, the IR spectra of the samples were studied, after which the dependence of the intensity of absorption peaks on the concentration of urea was analyzed. The aim of the work was to evaluate the possibility of using IR spectrometry in the medium range to identify carbamide in milk. As a result of the research, a correlation was found between the level of urea and the characteristics of the IR spectra. The most significant result was the detection of a specific absorption band unique to urea. This allows not only to quantify its impurity, but also to confirm its presence even at low concentrations.