Gogov I, Ilieva R, Slavchev G
Vet Med Nauki. 1980;17(3):100-6.
The studied were carried out in 360 samples of unboiled milk and 1080 samples of pasteurized milk taken from three processing and distributing dairies having a different capacity and equipment. It was proved that the content of psychrotrophic microorganisms in unboiled milk from the three dairies varied from 120000 up to 200000 in 1 cm3 and was in close connection with the seasons of the year. The conditions applied for pasteurization in the three dairies killed (with the exception of those forming spores) nearly all psychrotrophic bacteria. The secondary seeding of the pasteurized milk by means of psychotrophics was carried out after the pasteurization along the whole technological route till its packing. The pasteurized milk packed in bottles showed a contamination with psychrotrophic microorganisms 4-6 times higher than that of milk packed in plastic bags. In the unboiled and in the pasteurized milk we found the psychrotrophic microorganisms of the species: Pseudomonas--respectively 64% and 53.8%, Micrococcus--8.2% and 30.7%, Enterobacter--9.8% and 2.6%, Bacillus--6.6% and 2.6%, Flavobacter--1.6% and 1.3% and Torula--2.6%. A comparatively high percentage (37.7%) of the isolated strains the psychrotrophic bacteria were lipolytic in the unboiled milk, 24.6%--proteolytic and 9.8% were simultaneously proteolytic and lipolytic. In the pasteurized milk 11.5% of the strains were lipolytic and 5.13% were proteolytic.
研究是在从三个不同规模和设备的加工及配送乳制品厂采集的360份生牛奶样本和1080份巴氏杀菌牛奶样本上进行的。结果证明，来自这三个乳制品厂的生牛奶中嗜冷微生物的含量在每立方厘米120000至200000之间，且与一年中的季节密切相关。这三个乳制品厂采用的巴氏杀菌条件杀灭了（形成孢子的除外）几乎所有嗜冷细菌。巴氏杀菌牛奶在整个工艺流程直至包装过程中，在巴氏杀菌后受到嗜冷菌的二次污染。装在瓶子里的巴氏杀菌牛奶受到嗜冷微生物的污染比装在塑料袋里的牛奶高4至6倍。在生牛奶和巴氏杀菌牛奶中，我们发现了以下种类的嗜冷微生物：假单胞菌——分别为64%和53.8%，微球菌——8.2%和30.7%，肠杆菌——9.8%和2.6%，芽孢杆菌——6.6%和2.6%，黄杆菌——1.6%和1.3%，以及圆酵母——2.6%。在生牛奶中，相对较高比例（37.7%）的分离嗜冷细菌菌株具有脂肪分解能力，24.6%具有蛋白分解能力，9.8%同时具有蛋白分解和脂肪分解能力。在巴氏杀菌牛奶中，11.5%的菌株具有脂肪分解能力，5.13%具有蛋白分解能力。
