Investigation of the Effect of Starter type and Formulation on Physicochemical and Sensory Properties of Concentrated Yoghurt Using Mixture Design and Two-stage Clustering Method

In this study, the effect of starter type (probiotic and non-probiotic), milk (58 to 80%), cream (1 to 33%), whey powder (3 to 7%) and milk protein concentrate (6 to 12%) on acidity, pH, viscosity and sensory properties (flavor, color, texture and overall acceptance) of yogurt were evaluated using mixture design and then treatments were clustered and analyzed using two-stage clustering. The results showed that the linear effects of treatments (milk, cream, whey powder and protein concentrate) on all responses of the samples were significant, so increasing milk cream led to an increase in pH, viscosity, texture, color and flavor and overall acceptance and decreased acidity of the samples. Increasing whey powder and milk protein concentrate also led to increasing acidity and decreasing pH, viscosity, texture, color and overall acceptance of the samples. The linear effect of the starter type had no significant effect on the responses of the samples. Two-stage data clustering also divided the treatments of this study into two separate clusters and showed that whey powder and milk protein concentrate are not suitable substitutes for fat.