Effect of total bacteria number and protein content of raw milk on probiotic bacteria multiplication

Abstract

Considering that the quality of raw milk is a prerequisite condition to obtain a good quality probiotic yoghurt, our studies aimed the measurement of milk factors which can affect the multiplication of probiotic lactic acid bacteria (LABs) Lactobacillus acidophilus (LA-5) and Bifidobacterium (BB-12) strains from Christian Hansen company (Danmark). We studied comparatively raw and pasteurized milk chemical composition and the correlations between the spontaneous microbial flora (expressed in CFU=colony formatting unit) found in milk samples and the impact of this flora on the multiplication of LABs. We investigated as well the effect milk proteins on pH and LAB development, the influence of NTG (number of total bacteria), on lactic fermentations and LA-5 (Lactobacillus acidophilus) and BB-12 activities. Generally the BB-12 (Bifidobacterium) activities were lower comparing with LA-5 and multiplication of both strains was reversely correlated with NTG values. Protein content of raw milk has minor influence on LA-5 and BB-12 multiplication , but it influences structure of probiotic yogurt.