SOME CHEMICAL AND BACTERIOLOGICAL CHARACTERISTICS OF REGIONAL CHEESESFROM ASTURIAS, SPAIN

One hundred and one samples of six representative short-ripened cheese s (five homemade and one industrially manufactured) were collected ove r 1 year in several supermarkets in Asturias and analyzed for mesophil ic plate counts, coliforms, enterobacteria, coagulase-positive staphyl ococci, the presence of species of Salmonella and Listeria, pH, moistu re, NaCl, and a(w). Chemical characteristics varied, largely depending on the type of cheese. The percentages of moisture and NaCl ranged fr om 36.11 to 48.91 and from 1.16 to 2.08 respectively. The a, values we re between 0.95 and 0.99. Acidification was quite efficient, all chees es having mean pH values between 4.56 and 5.39. None of the samples yi elded Salmonella spp. Coagulase-positive staphylococci were detected i n two cheeses, in one reaching levels up to 10(6) CFU/g. Listeria spp. contaminated 11.8% of the cheeses, with Listeria monocytogenes isolat ed from 8.91% and Listeria innocua from 4.95% of the samples. The dist ribution of Listeria spp. varied largely depending on the type of chee se: 41% of the samples contaminated with L. monocytogenes were obtaine d from one type of cheese which had the lowest pH and NaCl values and the highest a, and moisture levels of the cheeses analyzed. However, L . monocytogenes was absent from another type of cheese, which showed i ntermediate chemical characteristics. High levels of coliforms and ent erobacteria (4 to 5 log CFU/ml) were detected in the five homemade che eses and were statistically associated with the presence of Listeria s pp. and L. monocytogenes. Cold enrichment was unsuccessful for the rec overy of Listeria spp. from the cheeses analyzed, while a combination of different enrichment methods resulted in the best procedure for det ecting all positive samples. This study shows that L. monocytogenes an d coagulase-positive staphylococci are present in short-ripened cheese s consumed in Asturias. Adequate measures to prevent contamination dur ing cheese making will probably result in safer products.