A survey of the microbiological quality of frozen unpasteurised goats' milk in Queensland, Australia

An investigation of the microbiological quality of frozen unpasteurised goats' milk produced at three south-east Queensland dairies was carried out. A total of 269 milk samples were examined. All samples were analysed for coliforms, 214 for aerobic bacteria, 74 for coagulase-positive Staphylococci and Escherichia coli, 63 for Campylobacter, 55 for Salmonella and Listeria, and 34 for staphylococcal enterotoxin and Escherichia coli O157:H7. No pathogens, toxins or faecal indicators (E. coli), were detected in any sample. A total of 90.2% of samples had standard plate counts (SPC) of greater than 2 log cfu/g. For the samples with counts greater than 2 log cfu/g, the mean was 3.8 log cfu/g, and counts at the 90th, 95th and 99th percentiles were 4.2, 4.3, and 4.8 log cfu/g, respectively. The maximum number of bacteria in any sample was 4.9 log cfu/g. Coliform counts were greater than 1 log cfu/g in 7.4 % of cases. Of these samples, the mean was 1.4 log cfu/g, and counts at the 90th, 95th and 99th percentiles were 1.9, 2.0, and 2.1 log cfu/g, respectively. The maximum number of coliforms in any sample was 2.3 log cfu/g. There were differences in mean bacterial counts between seasons, with SPC counts significantly higher in winter (p<0.05) and coliform counts significantly higher in summer (p<0.05). The microbiological quality of unpasteurised goats' milk as found in the present study is generally better than that reported in earlier work. These data can be used for risk assessments aimed at determining the safety of unpasteurised goats' milk in Queensland.