Occurence and Detection of Aerobic Sporulating Microorganisms in Raw Cow’s Milk

The occurrence and system of detection of mesophilic and psychrotrophic aerobic sporulating microorganisms (MPAS) in raw cow’s milk were studied. Samples of raw cow’s milk from bulk tanks were collected 21 times from 14 farms during one year. MPAS assessment is based on inactivation of milk sample at the temperature of 80–82°C for 30 minutes followed by incubation in cultivation dishes at 30±1°C for 3 days for mesophilic aerobic sporulates (MAS), and at 6.5±1°C for 10 days for psychrotrophic aerobic sporulates (PAS). The total count of MPAS was within the span of 2.5–340 CFU/ml. Average value of MPAS was 59.4 CFU/ml, and variation coefficient was 93.1%. MPAS count for mesophilic and subsequently strictly psychrophilic microorganisms (MAS + SPAS) detected in the same incubation dishes enables to exclude overestimation of results as sporulates are capable of growing at both incubation temperatures. The average count (MAS + SPAS) was 56.9 CFU/ml representing 95.8% of the number of sums of individual dishes at two temperatures (MAS+PAS). Correlation coefficient of these two types of results (r = 0.99) provides evidence of close dependence which is expressed by linear regression equation y = 0.9773x. We can consider the method using at first 30±1°C and subsequently 6.5±1°C (MAS + SPAS) as more appropriate than the opposite order of cultivation temperatures because of better regression coefficient of linear dependence and higher correlation coefficient in relation to the sum of independent incubations (MAS + PAS).