Microbiological quality of milk from two processing plants in Gaborone Botswana

Raw and bottled commercial pasteurised milk from two processing plants in Gaborone, Botswana were assessed for mesophilic, psychrotrophic, proteolytic and lipolytic bacteria. Proteolytic-psychrotroph counts ranged between 101 and 105 CFU/ml in both milk types. Corynebacterium pseudodiphtheriticum (44%) and Bacillus brevis (72%) predominated in raw and commercial pasteurised milk respectively. Trypsin and chymotrypsin were detected in isolates of Bacillus circulans, Pseudomonas cichorii and Micrococcus lentus. Esterase and esterase lipase activity were observed in Corynebacterium nitrilophilus, Pseudomonas fragi, B. circulans, Bacillus coagulans, and M. lentus. The study demonstrated that post-process contamination and ineffective pasteurisation compromised the quality and shelf life of pasteurised milk