Growth of Lactic Acid Bacteria in Milk for the Preparation of Functional Frozen Misti Dahi (Sweet Curd)

Abstract

This study was conducted to evaluate the growth of lactic acid bacteria in the milk for preparation of functional frozen Misti Dahi (Sweet Curd). The identity of the culture was carried out by macroscopy (morphology) and microscopy (Gram straining) method. Cultures were cultivated in 10% (w/v) reconstituted skim milk to check their pH, titratable acidity and lactic acid bacteria count during 0, 3, 6, 9 and 12 hours fermentation at 370C. On the basis of all of the identification tests one strain was identified as Lactobacillus helveticus, and the other strain was identified as Streptococcus thermophilus. The pH of fermented milk decreased from pH 6.42 to 3.11and titratable acidity increased from 0.10% to 0.98% by Lactobacillus helveticus, Streptococcus thermophilus and combination of Lactobacillus helveticus and Streptococcus thermophilus, when incubated for 12 h at 37°C. The number of lactic acid bacteria counts in fermented milk was maximized at this incubation condition. Lactobacillus helveticus, Streptococcus thermophilus and combination of Lactobacillus helveticus and Streptococcus thermophilus strains produced 7.80 to 8.85log cfu/ml of lactic acid in fermented milk at 370C. The present findings suggests that the both the Lactobacillus helveticus and Streptococcus thermophilus cultures alone or in combinations are potential to be used for the preparation of functional frozen Misti Dahi (Sweet curd).