La flore microbienne de laits crus de vache : diversité et influence des conditions de production

Abstract

Raw cowmilk microflora: diversity and influence of conditions of production . The microbial composition of 158 raw cow milk samples taken from 27 farms located in the French Alps areawas determined. Microbial analyses included the totalmesophilic aerobic bacteria count as well as numeration of some useful cheesemaking microorganisms (lactic acid bacteria, halophilic bacteria, propionic acid bacteria…), spoilage bacteria (Pseudomonas, enterobacteriaceae, Clostridium spp.) and some of the pathogenic bacteria (coagulase positive staphylococci, Escherichia coli). Milk samples were of good overall microbial quality (mean value less than 10 000 cfu.mL–1) and had different contents of useful cheesemakingmicroorganisms or spoilage bacteria. Five different groups of milks were then separated according to their total count and to their relative contents in useful cheesemaking and spoilage microorganisms. When incubated at 37 oC for 24 h without any starters addition, milks of the different groups did not have the same ability to produce acid and to coagulate. At the farm level,milk suppliers practices were studied. Farmers differed by theirway ofwashing the milking equipment and by their pre-milking and post-milking udder preparation. Combination of these practices influenced the microbial load and composition of the milk produced.