Effect of Using Different Concentrations of Whey Protein Isolate and Locust Bean Gum on Quality Properties of Non-fat Set-Type Yogurt

The use of milk fat substitutes in the manufacturing of dairy products is highly considerable in order to decrease in suffering chronic diseases and amount of calorie intake. However, semi-fat or non-fat dairy products have defects in their texture and sensory properties. The aim of this study was to investigate the effect of using whey protein isolate and locust bean gum as fat replacers on quality properties of non-fat yogurt. For this purpose, set-yogurt samples were manufactured using non-fat milk (lees than0/1%) and different concentrations of  locust bean gum and whey protein isolate. Control samples were also manufactured using whole milk (3% fat) and non-fat milk (less than 0/1%) without locust bean gum or whey protein isolate. The manufactured samples were stored in (4±1°C) for 15 days and their physicochemical, texture and sensory properties  were analyzed during storage. The results showed that the use of different concentrations of locust bean gum and whey protein isolate significantly influenced the  pH, acidity, water holding capacity, synersis, viscosity, hardness, springiness, cohesiveness, adhesiveness, appearance and color, ,texture and consistency , odor and flavor  and total sensory scores (p<0.05). While water holding capacity, acidity, hardness and viscosity were increased significantly during storage in all samples, synersis, pH and odor and flavor decreased significantly (p<0.05). In conclusion, the results of different analysis showed that use of the 10gr.L-1whey protein isolate, 5gr.L-1 whey protein isolate and 0.25gr.L-1 locust bean gum + 10gr.L-1 whey protein isolate instead of milk fat in formulation of non-fat set type yogurt led to manufacturing of final product with the most acceptable physicochemical, texture and sensory properties.