This study analyzed the effect of pH (X1), temperature (X2) and inulin amount (X3) on transformation of isoflavones (daidzin and daidzein) to equol in soymilk fermented with Bifidobacterium spp. All responses significantly (p 0.05) difference between the experimental and predicted values, suggested the suitability of established models in explaining the daidzin and daidzein transformation to equol as a function of pH, temperature and inulin.