Optimization and development of Misti dahi (sweetened yoghurt) from mixture of cow and goat milk

The present study aims to optimize the relative proportion of cow and goat milk and sugar percent in preparation of misti dahi (sweetened yoghurt). Seventeen experimental runs were conducted with varying levels of independent variables viz. cow milk (60-100v/v), goat milk (20-40v/v) and sugar (8-14%), as generated by Box-Behnken experimental design (BBD). The responses investigated were titratable acidity, syneresis, firmness and overall acceptability of sweetened yoghurt. Response surface methodology (RSM) was used to determine the optimum cow and goat milk proportion and sugar percent. The RSM results showed that the experimental data could be adequately fitted to a second-order polynomial model with correlation coefficients (R²) of more than 0.94. The study revealed that the effect of all the factors were significant on the responses. The optimum formulation obtained using desirability function was cow and goat milk 73.59 and 18.99 (v/v) respectively and sugar 14%. The values of responses at optimum formulation were, 0.71% titratable acidity, 18.00% syneresis, 3.59N firmness, and 7.97 sensory acceptability. These predicted values were validated with experimental values and found no significant difference.