Yousef Ahmed E, Marth Elmer H
Department of Food Science and the Food Research Institute, University of Wisconsin-Madison, Madison, Wisconsin 53706.
J Food Prot. 1988 Jan;51(1):12-15. doi: 10.4315/0362-028X-51.1.12.
Colby cheese was made from pasteurized whole milk to which Listeria monocytogenes (strain V7 or California) was added. Cheese was stored for 140 d at 4°C. Numbers of L. monocytogenes in newly-made cheese were 1.27 orders of magnitude (average) higher than in milk from which cheese was made. This indicates the bacterium did not grow to any appreciable extent during the manufacture of cheese. A minor portion (2.4%) of the population of Listeria in the cheese vat escaped in the whey and the rest was entrapped in the curd. Early during storage, numbers of Listeria in the cheese remained relatively constant for a time that depended on the strain used. Numbers of Listeria in cheese decreased steadily thereafter at a rate that depended mainly on composition of the cheese. After 140 d of storage, higher numbers of Listeria remained in cheese when (a) a higher rather than lower concentration of the microorganism was present in milk, (b)cheese with a higher rather than lower moisture content was produced, and (c) strain V7 rather than California was added to milk.
科尔比奶酪由巴氏杀菌全脂牛奶制成，并添加了单核细胞增生李斯特菌（菌株V7或加利福尼亚株）。奶酪在4°C下储存140天。新制奶酪中单核细胞增生李斯特菌的数量比制作奶酪所用牛奶中的数量平均高1.27个数量级。这表明该细菌在奶酪制作过程中没有显著生长。奶酪桶中一小部分（2.4%）的李斯特菌随乳清流失，其余的则被困在凝乳中。在储存初期，奶酪中李斯特菌的数量在一段时间内保持相对稳定，这取决于所使用的菌株。此后，奶酪中李斯特菌的数量以主要取决于奶酪成分的速率稳步下降。储存140天后，当（a）牛奶中存在较高而非较低浓度的微生物时，（b）生产的奶酪水分含量较高而非较低时，以及（c）向牛奶中添加的是菌株V7而非加利福尼亚株时，奶酪中残留的李斯特菌数量较多。
