Raw milk intended for the production of different types of pasteurized milk: are there any differences in terms of microbial hazards?

The main factor affecting microbial composition of raw milk is animal feed, and there is an increasing trend towards pasture-based organic systems, which increase the exposure to environmental bacteria. However, little is known about the microbial risks of different types of raw milk. In the present study, the microbial quality of raw milk intended for the production of standard, high-quality, organic, and organic hay pasteurized milk was assessed. All raw milk batches were compliant with European regulations for somatic cells and total bacterial count. However, a wide standard deviation was observed, with single raw milk samples exceeding the limits. Nine and three samples exceeded the limits of 300.00 cells/mL for somatic cells and 100.000 CFU/mL for total bacterial count, respectively. Moreover, 9, 8, and 3 samples were above 4 log10 CFU/mL for Enterobacteriaceae, 3 log10 CFU/mL for Escherichia coli, and 4 log10 CFU/mL for coagulase-positive Staphylococci (CPS), respectively. Overall, 6% of high-quality raw milk samples, 29% of organic samples, 20% of organic hay samples, and 23% of standard raw milk samples exceeded at least one of the above-mentioned limits. No samples tested positive for Salmonella spp., whereas two organic samples tested positive for Listeria monocytogenes. No statistically significant differences were observed in relation to seasons except for CPS, which showed a higher load in winter and autumn in comparison to summer and spring. Results suggest the usefulness of including Enterobacteriaceae as a new indicator and/or of reducing the threshold of the current acceptable total bacterial count, especially for raw milk intended for the production of organic milk.