Stability of lactic acid bacteria and physico-chemical properties of pasteurized cow's and goat's milk

This study was done to determine the effect of pasteurization on the stability of lactic acid bacteria and its enzyme, and also its relation with physico-chemical properties in raw and pasteurized cow's and goat's milk. Most of the physico-chemical properties (pH, protein, ash and fat) were highest in pasteurized goat's milk. The total viable count for plate count of the bacterial concentration was higher in both pasteurized cow's and goat's milk which were 2.48 log CFU/ml. This was followed by raw cow's milk (1.59 log CFU/ml) and raw goat's milk (0.65 log CFU/ml). There was no yeast and mould detected in both raw and pasteurized cow's and goat's milk, respectively. Lactic acid bacteria (LAB) was found significantly higher in raw milk compared to pasteurized milk and higher macronutrients (proximate composition) could be considered as one of the factors for the survival of LAB. Interestingly, based on API ZYM assay kit result, there were nine different enzymes were detected in all samples which were leucine arylamidase, valine arylamidase, cystine arylamidase, trypsin, alpha-chymotrypsin, naphthol-AS-BI-phosphohydrolase, alpha-glucosidase, beta-glucosidase and acid phosphatise. This result revealed that different types of lactic acid bacteria were detected in treated and non-treated milk samples produced by different animals.