CHARACTERIZATION AND EXTRACELLULAR ACTIVITY OF PSYCHROTROPHIC BACTERIA ISOLATED FROM VILLALON CHEESE (FRESH VARIETY OF SPANISH SHEEPS MILK CHEESE)

The incidence of psychrotrophic bacteria was investigated in a Spanish fresh ewes' cheese (Villalon). Counts of mesophiles and psychrotrophs were (log cfu/g) 5.72 +/- 1.10 and 3.90 +/- 1.01, respectively, for f actory cheeses made from pasteurized-milk. Figures for hand-made chees es made from raw-milk were 7.35 +/- 0.48 and 6.94 +/- 0.65, respective ly. A total of 59 representative psychrotrophic isolates were characte rized and tested for protease and lipase production at 7 and 30 degree s C. The strains were assigned to Enterobacteriaceae (predominant in r aw-milk cheese), heterofermentative lactic acid bacteria (dominant in pasteurized-milk cheese and absent in raw-milk cheese) and Pseudomonas . More than 73% of the Enterobacteriaceae produced both proteolytic an d lipolytic enzymes at either 30 or 7 degrees C. This percentage is co nsiderably higher than those previously reported. The seven isolates o f pseudomonads investigated produced proteases at 7 degrees C and six were positive at 30 degrees C; lipolytic activity was shown by five of the isolates at both temperatures. Among the heterofermentative lacti c acid bacteria seven of the ten isolates were proteolytic at 30 degre es C.