Anderson Melisa, Hinds Patrice, Hurditt Stacyann, Miller Princena, McGrowder Donovan, Alexander-Lindo Ruby
Department of Pathology, Faculty of Medical Sciences, University of the West Indies, Kingston 7, Jamaica.
Asian Pac J Trop Biomed. 2011 Jun;1(3):205-11. doi: 10.1016/S2221-1691(11)60028-2.
To determine the presence and levels of microbes in unexpired pasteurized milk from randomly selected supermarkets in Kingston, Jamaica.
The quantitative study used a stratified random sampling technique in the selection of the 20 representative milk samples from six (6) supermarkets. Microbiological tests such as methylene blue reduction, standard plate count (SPC), coliform plate count (CPC), purity plate culture, gram staining and biochemical tests were performed to examine the microbes in purchased unexpired pasteurized milk.
One sample (BCr016) had a pH of 4.0, a rancid odour and curdled appearance. It decolourized within one hour during the methylene blue reduction test and was classified as class 4 milk. Seven of the samples were sterile with no microbe growth on the plate count agar and violet red bile salt agar (VRBA). The milk samples that appeared to be safe for consumption were all 10, 11, 12 and 13 days before expiration. The VRBA sample BCr016, had a colony count of 13 400 CFU/ mL. There was the presence of Escherichia coli in sample LCr021 which had a standard plate count of 1 580 SPC/mL and a coliform count of 500 CFU/mL. Enterobacter sp. was present in colonies from BCr016 and all the other milk samples.
Unacceptable levels of Enterobacter spp. and Escherichia coli were found in most of the samples. Effective measures to ensure safe milk for human consumption such as the phosphatase test and methylene blue reduction test should be routinely performed on each batch of milk processed by dairy plants.
确定从牙买加金斯敦随机挑选的超市中未过期巴氏杀菌乳中的微生物存在情况及含量水平。
这项定量研究采用分层随机抽样技术，从六家超市选取了20份具有代表性的牛奶样本。进行了诸如亚甲蓝还原试验、标准平板计数（SPC）、大肠菌群平板计数（CPC）、纯培养平板培养、革兰氏染色和生化试验等微生物学检测，以检测购买的未过期巴氏杀菌乳中的微生物。
一个样本（BCr016）的pH值为4.0，有酸败气味且出现凝乳现象。在亚甲蓝还原试验中，它在一小时内褪色，被归类为4级牛奶。七个样本无菌，在平板计数琼脂和紫红胆盐琼脂（VRBA）上没有微生物生长。看起来可安全食用的牛奶样本都是在过期前10、11、12和13天的。VRBA样本BCr016的菌落计数为13400 CFU/mL。样本LCr021中存在大肠杆菌，其标准平板计数为1580 SPC/mL，大肠菌群计数为500 CFU/mL。BCr016和所有其他牛奶样本的菌落中均存在肠杆菌属。
在大多数样本中发现了不可接受水平的肠杆菌属和大肠杆菌。乳制品厂应对每批加工的牛奶常规进行有效措施，如磷酸酶试验和亚甲蓝还原试验，以确保供人类食用的牛奶安全。
