Associative growth behavior of dahi and yoghurt starter cultures with Bifidobacterium bifidum and Lactobacillus acidophilus in buffalo skim milk

We report here for the first time variations in the viability and biochemical activity of dahi and yoghurt cultures, when grown together with therapeutic cultures, such as Lactobacillus acidophilus I and Bifidobacterium bifidum R, in buffalo skim milk. Nearly one log reduction in mesophilic lactic count was observed in dahi supplemented with probiotic cultures after 18 h of incubation at 30 °C. Associative growth increased the titratable acidity (TA) of dahi marginally (from 0.93 to 1.18 % lactic acid) but reduced the TA in yoghurt (from 1.68 to 1.44 % lactic acid). Probiotic culture supplementation reduced volatile acidity (VA) (from 36.0 to 15.8 ml) and diacetyl (from 4.05 to 2.80 ppm) and tyrosine (from 0.46 to 0.36 μg tyrosine/g curd ) content in dahi, whereas it increased VA (from 8.2 to 8.6 ml of 0.01 % NaoH/50 g) and acetaldehyde (from 28.4 to 34.6 ppm) production in yoghurt. Based on these results, the associative growth had no effect on proteolytic activity of probiotic yoghurt.