INCIDENCE OF AEROBIC SPOILAGE- AND PSYCHROTROPHIC BACTERIA IN NON-PASTEURISED AND PASTEURISED BOVINE MILK FROM MASERU

Abstract

The presence of pathogenic bacteria in milk is a possible source of food-borne diseases. One hundred and sixty non-pasteurised and forty pasteurised milk samples from the Maseru area were analysed for the presence of bacteria. It is recommended by legislation that milk be free from pathogenic bacteria, and microbial counts must be within the ranges as stipulated in Regulation 1555 of 21 November 1997. Eighty seven of the non-pasteurised milk samples had high total aerobic bacterial counts that were not within the stipulated range for microbial counts as outlined in Regulation 1555, whereas twenty seven pasteurised milk samples had unacceptably high aerobic bacterial counts. Unacceptably high counts of E. coli were detected in thirty five of the non-pasteurised samples. Bacterial phosphatase was detected in seven of the pasteurised samples, indicating possible post-processing contamination. Listeria monocytogenes was isolated from five non-pasteurised milk samples and Listeria innocua was isolated from one sample. The presence of psychrotrophic Listeria could contaminate the milk processing plant rendering pasteurised milk unsafe for human consumption. Community members should be informed regarding the dangers of consuming non-pasteurised milk. Smallscale farmers should be educated regarding the dangers of Listeria infection in the herds.