Psychrotrophic microorganisms in raw and pasteurized milk
Gogov, I.; Ilieva, R.; Slavchev, G.
Veterinarno-Meditsinski Nauki 17(3): 100-106
1980
ISSN/ISBN: 0324-1068 PMID: 6894344 Document Number: 163055
A total of 360 samples of raw milk and 1080 samples of pasteurized milk were examined during 1 yr in the Sofia, Pazardzhik and Botevgrad dairy factories in Bulgaria. Heat treatment was at 84-86 deg C for 20 s, 80-87 deg C for 20 s, and 74-76 deg C for 20 s in the 3 factories resp., the pasteurized milk being packaged in polyethylene sachets in Sofia and in glass bottles in the other 2 localities. Total psychrotrophic counts in raw milk were similar in the 3 factories and ranged from 120 000 to 2 million/ml, counts being closely related to season of the yr. Samples taken from the cooling sections of the pasteurizers contained psychrotrophic microorganisms only in isolated cases (at less than or equal to 10/ml), but considerable secondary contamination occurred after packaging; it was 4-6X greater in bottles than in sachets, and also showed relationship with season. Overall % incidences of psychrotrophic microorganisms in raw and pasteurized milks were resp.; Pseudomonas, 64.0 and 53.8; Micrococcus, 8.2 and 30.7; Enterobacter, 9.8 and 6.4; Aeromonas, 9.8 and 2.6; Bacillus, 6.6 and 2.6; Flavobacterium, 1.6 and 1.3; and Torula spp. 0 and 2.6. Incidence of lipolytic and proteolytic psychrotrophs in raw milk were 24.6 and 9.8% resp. and in pasteurized milk, 11.5 and 5.1% resp.