Farm Level Milk Adulteration: Changes in the Physicochemical Properties of Raw Cow’s Milk after the Addition of Water and NaCl

Abstract

Sustainable food security assumes the elimination of food resources adulteration that is already present on farms. This paper is focused on changes in physical and chemical properties of raw cow’s milk treated by the addition of water and NaCl. The main studied factor is the freezing point of milk, which is strongly influenced by the chosen treatment. Adulteration of milk by water can be detected by the changed freezing point of the milk, but this can be brought within the range of standardized limits by the addition of NaCl. Determining the concentration of chloride ions in milk by the titration method is a proxy for the added NaCl. The analysis of raw cow’s milk from 17 agricultural farms in Southwest Slovakia revealed a negative correlation between the content of chlorides and the freezing point. In another laboratory experiment, the differences in the milk freezing points were statistically significant in the samples treated with different amounts of NaCl. The relationship of chlorides and the freezing point to other milk components (minerals, lipids, proteins, solids-not-fat, lactose, pH, and milk acidity after Soxhlet–Henkel) were analysed, as well. The results showed that the chosen method of chlorides detection to identify the adulteration of milk, by added water and NaCl, was not effective due to the unstable composition of milk and uncertainty in measurements (the coefficient of determination was very low, R2 = 0.3022).