The presence of yeasts, moulds and aflatoxin M1 in raw milk and cheese in Slovenia

The level of microbiological contamination with yeasts and moulds in 60 samples of raw milk and 40 samples of curd, soft salted or non-salted cheese and semi-hard cheese manufactured by small artisan food-processing plants, collected in autumn and winter season was evaluated. The yeasts were present in 95.0% of raw milk samples with the mean concentration of 1.7 log10 cfu/ml. Moulds were found in 63.3% of raw milk samples, their mean concentration was 0.6 log10 cfu/ml. Isolated mould strains belonged to genera Geotrichum (51.5%), Aspergillus (33.8%), Mucor (5.9%), Fusarium (2.9%) and Penicillium (2.9%). Both, yeasts and moulds were isolated from 60% of tested cheese samples with average concentrations 2.5 log10 cfu/g and 2.1 log10 cfu/g, respectively. The genera Geotrichum (91.9%), Moniliella (5.4%) and Aspergillus (2.7%) were most frequently isolated strains from tested cheese samples. None of the isolated Aspergillus strains with typical growth on AFPA medium produced aflatoxin M1 on YES or YGC medium supplemented with Methyl-β-cyclodextrin. The contamination with aflatoxin M1 in concentrations above 50 ng/kg was detected in 10% of cheese samples.