Correlation between physicochemical parameters of milk and risk of bacterial contamination: a case study in Armenia

Abstract

Milk is an essential component of human nutrition, and its safety and quality are influenced by its physicochemical parameters, including pH, fat and protein content, lactose concentration, and freezing point. These factors affect microbial stability and the risk of bacterial contamination. This study investigates the correlation between milk composition and microbial contamination risk by analyzing 70 milk samples from Armenian supermarkets. The physicochemical properties of the samples were evaluated using the Lactoscan Milkanalyzer, while microbial composition was determined through classical bacterial enumeration methods and VITEK® 2 compact ID/AST system. The results indicate that lower pH levels (e.g., 6.64–6.67) favor lactic acid bacteria, which may contribute to natural preservation, whereas higher pH levels (e.g., 6.78–6.87) increase susceptibility to spoilage bacteria such as Pseudomonas spp. and Bacillus spp. Additionally, higher lactose content correlated with the presence of Lactobacillus and Bifidobacterium species, which are considered beneficial. Importantly, no pathogenic bacteria (e.g., Salmonella, E. coli, Listeria monocytogenes) were detected in any of the samples, confirming the effectiveness of pasteurization and commercial processing. These findings highlight the importance of physicochemical properties in influencing microbial composition and emphasize the need for strict storage conditions to minimize spoilage risks.