The influence of ingredient supplementation on the textural characteristics of yogurt

Abstract

This investigation studied the effects of cysteine, whey powder (WP), whey protein concentrates (WPC1 and WPC2), acid casein hydrolysate (ACH) and tryptone on the textural properties of yogurts. Yogurt supplemented with 2% WPC1 was the firmest among all yogurt samples and its firmness was significantly higher (p<0.001) than other yogurts. The firmness of the control yogurt was similar to that supplemented with ACH, tryptone or cysteine at 50 and 250 mg/L level, but the firmness was significantly higher (p<0.001) with WPC1 and significantly lower (p<0.001) in yogurt made with WP and a high level of cysteine (500 mg/L). The viscosity of yogurt made with various ingredients showed significant differences (p<0.001) and an average increase in viscosity of ∼1.2 to 1.6 times was observed during refrigerated storage of 30 days, except for that supplemented with WPC2. The microscopic texture analyses of yogurt showed that the protein network of yogurt varied with various ingredients. Increased concentration of cysteine resulted in an irregular network of protein in the finished product and also affected the firmness and viscosity of the yogurt. The flocs and pores were large in the product supplemented with WPC. By contrast, an even and more regular protein network with very small flocs and pores was observed in the control yogurt and that supplemented with ACH or tryptone.