Santos J A, López-Díaz T M, García-Fernández M C, García-López M L, Otero A
Department of Food Hygiene and Food Technology, Veterinary Faculty, University of León, Spain.
Int J Food Microbiol. 1996 Dec;33(2-3):301-6. doi: 10.1016/0168-1605(96)01162-2.
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.
对西班牙一种新鲜母羊奶酪（比利亚隆奶酪）中的嗜冷菌发生率进行了调查。对于用巴氏杀菌乳制成的工厂奶酪，嗜温菌和嗜冷菌的计数分别为（log cfu/g）5.72±1.10和3.90±1.01。用生乳制成的手工奶酪的相应数字分别为7.35±0.48和6.94±0.65。共对59株具有代表性的嗜冷菌分离株进行了鉴定，并测试了它们在7℃和30℃下蛋白酶和脂肪酶的产生情况。这些菌株被归类为肠杆菌科（在生乳奶酪中占主导）、异型发酵乳酸菌（在巴氏杀菌乳奶酪中占主导，在生乳奶酪中不存在）和假单胞菌属。超过73%的肠杆菌科细菌在30℃或7℃下都能产生蛋白水解酶和脂肪水解酶。这一比例远高于此前报道的比例。所研究的7株假单胞菌分离株在7℃下能产生蛋白酶，6株在30℃下呈阳性；5株分离株在这两个温度下均表现出脂肪分解活性。在异型发酵乳酸菌中，10株分离株中有7株在30℃下具有蛋白水解能力。
