Mahari T, Gashe B A
Department of Biology, Addis Ababa University, Ethiopia.
J Dairy Res. 1990 May;57(2):233-8. doi: 10.1017/s0022029900026844.
The microorganisms present in raw and pasteurized milk and the sources of contamination in the milk after it had arrived at the processing plant in Addis Ababa were studied. The lowest count registered for raw milk samples was 4 X 10(7) cfu/ml while the highest was 1 X 10(9) cfu/ml. Pasteurized milk had mesophilic aerobic counts of 7 X 10(5) cfu/ml as it left the pasteurizing unit, but the population increased 2- to 4-fold as a result of subsequent contamination. Of the total counts in raw milk, psychrophilic, thermoduric and thermophilic organisms made up 98.1, 1.4 and 0.5% respectively. In pasteurized milk, the amounts were 53.0, 39.5 and 7.5% respectively. Samples of milk pasteurized in the laboratory contained only 74.5% thermoduric and 25.5% thermophilic organisms. The isolates mostly belonged to the genera Bacillus, Streptococcus, Lactobacillus, Arthrobacter, Alcaligenes, Aeromonas and Pseudomonas. Cocci were more predominant than rod-shaped bacteria. Of the rod-shaped bacteria, 73% were Gram-negative. The utensils holding the raw and pasteurized milk and the plastic sheets used for bagging the pasteurized milk contributed unusually high numbers of bacteria which were either thermoduric or thermophilic. More isolates were obtained from the pasteurized than the raw milk. The keeping quality of the pasteurized milk was found to be much lower than that of the laboratory-pasteurized milk.
对亚的斯亚贝巴加工厂收到的生牛奶和巴氏杀菌奶中存在的微生物以及牛奶污染来源进行了研究。生牛奶样本的最低计数为4×10⁷ cfu/ml，最高为1×10⁹ cfu/ml。巴氏杀菌奶离开巴氏杀菌单元时嗜温需氧菌计数为7×10⁵ cfu/ml，但由于后续污染，菌数增加了2至4倍。在生牛奶的总菌数中，嗜冷菌、耐热菌和嗜热菌分别占98.1%、1.4%和0.5%。在巴氏杀菌奶中，这些比例分别为53.0%、39.5%和7.5%。实验室巴氏杀菌的牛奶样本仅含有74.5%的耐热菌和25.5%的嗜热菌。分离出的菌株大多属于芽孢杆菌属、链球菌属、乳杆菌属、节杆菌属、产碱菌属、气单胞菌属和假单胞菌属。球菌比杆状细菌更占优势。在杆状细菌中，73%为革兰氏阴性菌。盛装生牛奶和巴氏杀菌奶的器具以及用于包装巴氏杀菌奶的塑料薄膜携带了数量异常多的耐热菌或嗜热菌。从巴氏杀菌奶中分离出的菌株比生牛奶中的更多。发现巴氏杀菌奶的保存质量远低于实验室巴氏杀菌的牛奶。
