The microbial content of unexpired pasteurized milk from selected supermarkets in a developing country.

OBJECTIVE

To determine the presence and levels of microbes in unexpired pasteurized milk from randomly selected supermarkets in Kingston, Jamaica.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.