Physological characteristics of psychrotrophic bacilli isolated from raw milk
2000
Mijacevic, Z.M. | Bulajic, S.B. (Univerzitet u Beogradu, Beograd (Yugoslavia). Fakultet veterinarske medicine, Katedra za higijenu i tehnologiju namirnica animalnog porekla)
The strains of genus Bacillus are often present as contaminents in raw milk. The isolation of psychrotrophic bacilli was conducted after incubation of 10 days at 7 +/- 1 deg C (isolation achieved only from milk samples which demonstrate the changes of Bacillus number at the start and after 10 days of incubation at 7 +/- 1 deg C). It was examined 56 psychrotrophic strains of bacilli isolated from raw milk. During incubation of 10 days at 7 +/- 1 deg C, in 50 samples of raw milk the number of bacilli increased from log 0.81 +/- 0.78 to 1.73 +/- 0.86, whereas in 6 samples the Bacillus number ranged from log 0.10 +/- 0.01 to 2.07 +/- 0.47. The differences between mean values of Bacillus number on the first and tenth days of incubation at low temperatures (psychrotrophic condition) were subjected to the t-test. It was noticed a highly significant difference. It was also found that 30.35% of the isolated strains were haemolytic, 64.28% degraded lecithin, 5.35% broke down gelatin, 78.57% degraded casein. A high percentage of isolated bacilli (97.07%) grew at pH 5.7 and 78.57% multiplied in the presence of 7% NaCl.
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