This study aimed to investigate the microbial quality of raw bovine milk from bulk tanks in Victoria. In Australia, the sale of milk for human consumption, that has not been pasteurized or equivalently heat-treated, is not permitted. Yet with the growing trend towards ‘natural’ and unprocessed foods, there is growing consumer demand for the product and an apparent increase in raw milk consumption. However, raw milk provides an environment for organisms to flourish and harbour a range of undesirable bacteria, culminating in foodborne illness and disease outbreaks. Assessment of the microbial quality of raw milk from bulk tankers can provide an indication of the food safety risks associated with bulk distribution of the product for human consumption. Bulk distribution could be a potential outcome if consumer demand increases.
Standardised culture based methods were used to test 100 raw milk samples from selected bulk tanks in Victoria for the following bacterial indicators; SPC, coliforms, coagulase positive Staphylococcus spp., Escherichia coli and pathogens; Campylobacter spp., Salmonella spp. and Listeria monocytogenes. Isolation rates were high for indicator bacteria; coliforms, coagulase positive Staphylococcus and E. coli at 70%, 75% and 60% respectively. The SPC recorded the highest mean viable count. Neither Campylobacter nor Salmonella were detected in this survey, however 1% of samples tested positive for L. mono. Arange of other organisms were also discovered following confirmatory testing using MALDI-TOF MS; Proteus mirabilis, Staphylococcus sciuri and Candida kefyr.
The results of this study indicate that there is a broad microbial diversity in raw bovine milk in Victoria which has implications on raw milk quality. The detection of L. mono and high isolation of other potentially harmful bacteria in this study indicate that the consumption of raw milk could result in foodborne disease and is therefore potentially unsafe for human consumption.