Development of probiotic milk drinks using probiotic strain isolated from local yogurt

Abstract

Two Lactobacillus spp. were isolated from four yogurt samples, which were identified on the basis of their colony morphologies grown on MRS (Man, Rogosa and Sharpe) media and on the basis of biochemical tests conducted in the laboratory. Based on biochemical characteristics and further screen, these two isolates were selected for probiotic screening and further study. Gram staining, Catalase test, Oxidase test, Sugar fermentation, Bile salt test, NaCl tolerance test and pH tolerance test were done in this regard. Based on the OD (Optical Density), it was evident that all isolates can grow from bile salt concentration 0.05% to 0.25% and pH 2.5 to pH 5.5, can be used as probiotic. For NaCl tolerance test, two isolates showed slight decrease of growth during 1% to 4% NaCl supplementation. After isolation of probiotic strain from yogurt, these strains were used for the development of probiotic milk drinks. These drinks were developed where one was controlled and other two were mixed with different concentration of fruit (mango juice). The analysis of probiotic milk drinks showed the highest fat content was 4.50%, protein content 3.99%, ash content 1.90%, acidity 0.78%. Storage studies were carried out for fifteen days at refrigeration temperature (5±10 ◦C) and samples were taken at an interval of three days. After 15 days acidity ranged between 0.91 to 0.95% and the counts of Isolate 1 and Isolate 2 ranged between 8.75∼9.55 log cfu/ml those were >5 log cfu/ml which makes probiotic milk drinks as health product. The sensory scores of the 10% mango juice mixed with probiotic milk drinks was significantly higher than that of the 5% (p<0.05) and the liking score ranged in the medium-like.