Effect of dairy farm and milk refrigeration on microbiological and microstructural characteristics of matured Serra da Estrela cheese

This work was aimed at enumerating the viable microorganisms in ripened Serra da Estrela cheeses, manufactured from both refrigerated and non-refrigerated milk, in various dairies located throughout the demarcated region. Scanning electron microscopy was used to analyze the microstructure, and thus aid in understanding possible differences in their microbiological profile. The cheeses were allowed to ripen under controlled conditions, and sampled at 60, 90, 120, 150 and 180 d following manufacture. Viable numbers of lactic acid bacteria, staphylococci, Enterobacteriaceae and yeasts were obtained following standard plate counting on a number of selective media. Lactococcus was the most abundant genus (above 10⁸ cfu g^-1 of cheese) up to 120 d of ripening. No significant microstructural differences were observed in cheeses manufactured in different dairies over the ripening process. However, microstructural differences were apparent between cheeses manufactured with refrigerated versus non-refrigerated milk.