Christen G L, Wang W C, Ren T J
J Dairy Sci. 1986 Nov;69(11):2769-78. doi: 10.3168/jds.S0022-0302(86)80728-7.
Thirty-four of 49 isolates of psychrotrophic bacteria produced extracellular lipase or protease when grown in rehydrated nonfat dry milk. The cell-free crude preparation from 50% of these had either heat-resistant lipase or protease; in 30% both enzymes were heat resistant. Eight isolates were selected for further evaluation of effect on ultra-high temperature processed milk. Free fatty acids and free amino groups of milk precultured with the bacteria increased at different rates depending on the isolate. Partially purified lipase from one of these bacteria (Acinetobacter sp.) caused free fatty acids to increase following ultra-high temperature processing when the milk was stored at 10, 21, or 32 degrees C for 4 wk. The increase was temperature dependent. Lipase activity of .0012 units/ml added prior to processing caused significant increases in free fatty acid at 21 and 32 degrees C in 4 wk.
49株嗜冷菌中的34株在复水脱脂奶粉中生长时会产生胞外脂肪酶或蛋白酶。其中50%的无细胞粗提物含有耐热脂肪酶或蛋白酶；30%的粗提物中两种酶都耐热。选择了8株菌进一步评估其对超高温处理牛奶的影响。与这些细菌预培养的牛奶中游离脂肪酸和游离氨基的增加速率因菌株而异。其中一种细菌（不动杆菌属）的部分纯化脂肪酶，在牛奶于10、21或32摄氏度储存4周后进行超高温处理时，会导致游离脂肪酸增加。这种增加与温度有关。在处理前添加0.0012单位/毫升的脂肪酶活性，在4周内会使21和32摄氏度下的游离脂肪酸显著增加。
