Milk fermented with mixed dahi cultures NCDC167, Lactococcus lactis ssp diacetylactis NCDC60 and two probiotic strains; Lactobacillus acidophilus NCDC14 and Lb. casei NCDC19 were evaluated after fermentation (14 h) and during 8 d storage at 7 degrees C. The beta-galactosidase activity was found to increase after fermentation leading to the hydrolysis of lactose and production of glucose, galactose and oligosaccharides; that subsequently decreased during storage. The viable counts of lactococci and lactobacilli decreased during storage yet remained >106 cfu/ml after storage. The results of present study indicate that all the selected cultures have ability to produce oligosaccharides (prebiotics) due to transgalactosidal and lactose hydrolysis activities of beta-galactosidase. The cultures developed an active synbiotic formula by maintaining sufficient probiotic viable counts to exert health benefits to the consumers.