Effect of exopolysaccharide-producing strains of Streptococcus thermophilus on technological attributes of fat-free lassi

Sixty-four exopolysaccharide-producing thermophilic lactic acid bacteria (LAB) were isolated from traditionally made Indian fermented milk products. On the basis of morphological and biochemical tests, these isolates were identified as the species of Lactobacillus, Streptococcus, and Enterococcus genera. Initial screening for technological attributes revealed that Streptococcus thermophilus IG16 was a promising isolate, and produced both capsular and ropy polysaccharides at the concentration of 211 mg/L. Exopolysaccharide produced by IG16 was a heteropolysaccharide containing rhamnose and galactose in a ratio of 5.3:1 and had a molecular weight of 3.3 × 10⁴ Da. Use of IG16 as a starter culture controlled whey separation and improved viscosity, flavor, consistency, and color and appearance of lassi. Use of IG16 resulted in lassi having optimal acidity, less syneresis, high viscosity, and better scores for flavor, consistency, and color and appearance.