MONITORING THE MICROBIOLOGY OF HIGH-QUALITY MILK BY MONTHLY SAMPLING OVER 2 YEARS

The concentrations of seven types of microorganism in the milk produce d by farms using high quality milking procedures were monitored monthl y. The most commonly encountered bacterium was Pseudomonas, whose conc entration varied greatly between samples, but lactococci, lactobacilli and yeasts were also present at more stable concentrations. Staphyloc occus aureus and beta-glucuronidase-positive Escherichia coli were occ asionally detected. Listeria monocytogenes was found in the samples fr om only one farm, while Yersinia enterocolitica was never detected. Th ere were seasonal variations in the concentrations of lactobacilli and yeasts over the 2 years monitored. The changes in certain bacteria (L actococcus, Lactobacillus) on any given farm were very similar from on e year to the next. The microbiological characteristics of the milk fr om the farms examined seemed to be fairly constant. The profiles of so me bacteria used for cheesemaking were relatively stable over time. It thus seems that the milk provided by different producers could be typ ed.