Exopolysaccharide-producing mesophilic lactic cultures for preparation of fat-free Dahi – an Indian fermented milk

Forty seven exopolysaccharide (EPS) producing mesophilic lactic acid bacteria have been isolated from Dahi and raw milk and selected cultures were evaluated for their influence on rheological and sensory properties of fat-free Dahi. Two isolates namely B-6 and KT-24 that showed promising technological attributes were identified as Lc. lactis subsp. lactis strains. B-6 produced 184±2 mg/l EPS in deproteinized whey medium compared with 193±1 mg/l by KT-24. EPS produced by B-6 was a heteropolysaccharide (consisting of glucose and mannose, 1:7·4) with molecular weight of 3·0×104 Da whereas KT-24 EPS was a homopolysaccharide (rhamnose) having molecular weight of 4·5×104 Da. Both EPS producing cultures showed significant changes in rheological and sensory properties of fat-free Dahi. Dahi prepared by these cultures was more viscous, adhesive, sticky, showed lower susceptibility to whey separation, and received higher sensory scores than Dahi prepared with non-EPS producing culture.