Effects of home-made boiling of bovine raw milk on its microbiological quality

The consumption of raw milk in Italy is allowed only “after boiling”. The aim of this research was to bet-ter understand how the heat treatment of raw milk performed at home by consumers assures their mi-crobiological safety. 50 samples of raw milk (each sample 500 ml) provided to consumers who regularly buy raw milk from self-service automatic vending machines were followed from delivery till to after do-mestic heat treatment. Heating was performed by consumers according to their habits. The 50 samples were exposed to different heat treatments of which the mildest was at 68.5 °C and the most intense was at 97.8 °C before switching off. The average of temperatures used was 89.5 °C and the mode was 93.2 °C. According to the different parameters of heat treatment observed, 35 samples of raw milk and 35 samples of heated milk were selected for microbiological and process indicator analyses. Total Microbial Count (TMC), total and fecal coliforms, Escherichia coli, Staphylococcus aureus and Bacillus cereus loads were determined. E. coli was isolated only from one sample of raw milk. No B. cereus nor S. aure-us were found in all samples. After heat treatment, 4 samples showed a residual TMC ranging between 1,7 CFU/ml and 3,2 CFU/ml, whilst the count of total and fecal coliforms were irrelevant. The test for alkaline phosphatase has showed negative in all samples of heated milk, while the test of lactoperoxi-dase was positive in 3 samples. Results indicated that the microbiological risk attributable to the consumption of home heated raw milk is low, if the consumer applies regularly a good heating process.