Characterization and extracellular activity of psychrotrophic bacteria isolated from Villalón cheese (fresh variety of Spanish sheep's milk cheese).
The incidence of psychrotrophic bacteria was investigated in a Spanish fresh ewes' cheese (Villalón). Counts of mesophiles and psychrotrophs were (log cfu/g) 5.72 +/- 1.10 and 3.90 +/- 1.01, respectively, for factory cheeses made from pasteurized-milk. Figures for hand-made cheeses made from raw-milk were 7.35 +/- 0.48 and 6.94 +/- 0.65, respectively. A total of 59 representative psychrotrophic isolates were characterized and tested for protease and lipase production at 7 and 30 degrees C. The strains were assigned to Enterobacteriaceae (predominant in raw-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 and lipolytic enzymes at either 30 or 7 degrees C. This percentage is considerably higher than those previously reported. The seven isolates of 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 lactic acid bacteria seven of the ten isolates were proteolytic at 30 degrees C.
Santos
J A
JA
Department of Food Hygiene and Food Technology, Veterinary Faculty, University of León, Spain.
López-Díaz
T M
TM
García-Fernández
M C
MC
García-López
M L
ML
Otero
A
A
D000818:Animals; D001419:Bacteria / Q000302:isolation & purification*; D002611:Cheese / Q000382:microbiology*; D004755:Enterobacteriaceae / Q000302:isolation & purification; D011549:Pseudomonas / Q000302:isolation & purification; D012756:Sheep