Tipparaju Sireesha, Ravishankar Sadhana, Slade Peter J
National Center for Food Safety and Technology, Illinois Institute of Technology Moffett Campus, 6502 South Archer Road, Summit-Argo, Illinois 60501, USA.
J Food Prot. 2004 Feb;67(2):378-82. doi: 10.4315/0362-028x-67.2.378.
The survival of Listeria monocytogenes V37 in vanilla-flavored yogurt (low-fat and nonfat) and soy milk (low-fat and Plus) stored at 8 degrees C for 31 days was investigated. Commercial samples of yogurt and soy milk were used. These samples were inoculated with either 10(4) or 10(7) CFU of L. monocytogenes per ml. Sampling was carried out every 3 to 4 days initially and was then carried out weekly, for a total storage time of 31 days. Each time a sample was collected, the pH of the sample was measured. After 31 days, low-fat plain, low-fat vanilla, and nonfat plain yogurt samples inoculated with 10(4) CFU/ml showed 2.5-log reductions in viable cell populations, and nonfat vanilla yogurt showed a 3.5-log reduction. For yogurt inoculated with 10(7) CFU/ml, reductions of 2.5 log CFU/ml were observed for plain low-fat and nonfat yogurts, and reductions of 5 log CFU/ml were observed for vanilla-flavored low-fat and nonfat yogurts. In vanilla-flavored and plain low-fat and Plus soy milk samples, cell counts increased from 10(4) and 10(7) CFU/ml to 10(9) CFU/ml at 7 and 3 days of storage, respectively, at 8 degrees C. Coagulation in soy milk samples was observed when the cell population reached 10(9) CFU/ml. In soy milk, the L. monocytogenes population did not change for up to 31 days. Vanillin had an inhibitory effect on L. monocytogenes in yogurt but not in soy milk.
研究了单核细胞增生李斯特菌V37在8℃下储存31天的香草味酸奶（低脂和脱脂）及豆奶（低脂和强化型）中的存活情况。使用了市售的酸奶和豆奶样品。这些样品每毫升接种10⁴或10⁷CFU的单核细胞增生李斯特菌。最初每3至4天进行一次采样，之后每周采样一次，总储存时间为31天。每次采集样品时，都要测量样品的pH值。31天后，接种10⁴CFU/ml的低脂原味、低脂香草味和脱脂原味酸奶样品的活菌数减少了2.5个对数级，脱脂香草味酸奶的活菌数减少了3.5个对数级。对于接种10⁷CFU/ml的酸奶，低脂原味和脱脂酸奶的活菌数减少了2.5 log CFU/ml，低脂香草味和脱脂香草味酸奶的活菌数减少了5 log CFU/ml。在香草味、原味低脂和强化型豆奶样品中，在8℃下储存7天和3天时，细胞计数分别从10⁴和10⁷CFU/ml增加到10⁹CFU/ml。当细胞数达到10⁹CFU/ml时，观察到豆奶样品出现凝固现象。在豆奶中，单核细胞增生李斯特菌的数量在长达31天的时间内没有变化。香草醛对酸奶中的单核细胞增生李斯特菌有抑制作用，但对豆奶中的该菌没有抑制作用。
