Altitude-related variations in microbiological quality of raw sheep milk and Vlašić cheese
This study investigated the effect of altitude on the microbiological quality of raw sheep milk and Vlašić cheese produced at three locations (Galica, Gostilj, and Paklarevo) on Mount Vlašić, Bosnia and Herzegovina. A total of 30 samples were analysed for the presence of Salmonella spp. and Listeria monocytogenes, and for the quantification of coagulase-positive staphylococci, aerobic mesophilic bacteria, Escherichia coli, Enterobacteriaceae, yeasts, and moulds. None of the samples contained Salmonella spp. or Listeria monocytogenes. In milk samples, significant differences were found among localities for moulds, with regression analysis indicating a significant negative correlation between altitude and mould count (p < 0.001, R² = 0.486). In Vlašić cheese samples, aerobic mesophilic bacteria were abundant at all sites, while regression analysis showed that E. coli (p < 0.001, R² = 0.472) and Enterobacteriaceae (p < 0.001, R² = 0.767) counts varied significantly with altitude. No significant correlations with altitude were observed for other microorganisms. The results suggest that differences among localities and altitude-related trends reflect the influence of variations in cheese-making practices on microbial dynamics in artisanal dairy systems. Improving hygiene control, as well as expanding altitude-based studies across different regions, could enhance both product safety and the preservation of traditional cheesemaking practices.