2.4. Viable cell counts (VCC) of B. bifidum
Cultures of B. bifidum were enumerated using MRS-LP agar.The formulation of MRS-LP was prepared according to
Vinderola et al. (2000) where 0.2% (w/v) of lithium chloride(solid–powder) and 0.3% (w/v) of sodium propionate (solid–
powder) were added to the MRS media (62 g/930 L dH2O,45 C). Yogurt samples (1 ml) were mixed with 9 ml of
0.15% sterile buffered peptone water (20 g/L dH2O). The mixture was thoroughly stirred and serial decimal dilutions were prepared by using buffered peptone water. One millilitre of diluted yogurt with buffered peptone water was mixed with 15 ml of autoclaved melted MRS–LP media using the pour plate method. The probiotic cultures were anaerobically incubated
(GasPak System-OXOID) at 37 C for 72 h. The viable
B. bifidum counts were calculated (Sivakumar and Kalaiarasu,
2010) as follow: