EFFECT OF SOYA AND WHEY PROTEINS ON THE SENSORY AND PHYSICOCHEMICAL PROPERTIES OF SET YOGHURT

Abstract

Recently, a focus on the utilization of whey and soya proteins has been receiving significant attention due to their nutritional value and their potential to enhance the functional characteristics of the dairy products. Set yoghurt was manufactured from standardized (4% fat) buffalo milk alone (control), or fortified with whey protein concentrate (WPC), soya protein concentrate (SPC) or their combination (MIX) and stored at 5±2 °C for 10 days. Sensory properties of the resultant yoghurt were evaluated one day after manufacturing. All treatments were analyzed when fresh and during storage period for pH-value, titratable acidity(TA) and syneresis. The pH-values and titratable acidity(TA) of yoghurt samples showed that both soya and whey proteins did not alter the rate of acid production in yoghurt. Acidity of samples treated with WPC during storage was significantly (P<0.05) higher, compared to control. Also, the addition of whey proteins and soya proteins or their combination resulted in reduction in the syneresis of yoghurt samples by about 17-25%, when compared with control at zero time. Fortification with soya proteins lowered appearance, taste and odor scores by 25, 37 and 35%, respectively, compared with the control. This negative effect of soya proteins on the sensory properties of yoghurt (SPC treatment) was improved when combined with whey protein in the MIX treatment. Therefore, it is recommended to add whey proteins to improve sensory and syneresis properties of soya yoghurt.