14A-31 |
Effect of polymerized whey proteins on consistency and syneresis of probiotic goat’s milk yogurt |
J. LI, Department of Nutrition and Food Sciences, University of Vermont, 305 Terrill Hall, Burlington, VT 05405 and M. Guo. Weak body and syneresis are the most common defects of yogurt products. It has been shown that gel formation can be achieved from polymerized whey proteins (WP-Polymers) by acidification. WP-polymers may improve the body texture and enhance the water-binding property of yogurt. The objective of this study was to examine the effects of WP-Polymers on the consistency and syneresis of probiotic goat’s milk yogurt. WP-Polymers were prepared by heating whey protein isolate solution (WPI, 8% protein, pH 7.0) at 90°C for 30 min. Three reconstituted goat milk (RGM) (12% total solids (TS) as control; RGM with 2.4% un-heated WPI; and RGM with 2.4% WP-Polymers) and one RGM with 16.7% TS were prepared and inoculated with 0.04% probiotic yogurt culture (including Lactobacillus acidophilus, Bifidobacteria and Lactobacillus subsp. casei). Inoculated milk was incubated at 43°C for 4.5h, cooled to 4°C in an ice-water bath with slow overhead stirring, and then placed at refrigerator (4°C). After overnight storage, the stirred yogurt samples were examined for viscosity, pH, syneresis, titratable acidity (TA), ash, lactose and protein contents. Incorporation of WP-Polymers significantly (P < 0.001) increased the viscosity (by 83%) and decreased the syneresis (by 25%) of the yogurt samples, whereas addition of un-heated WPI did not significantly affect the viscosity and syneresis compared to the control. There were no changes in pH, TS, ash, lactose and protein contents among yogurt samples with 12% TS. Yogurt with 16.7% TS had the lowest syneresis but did not improve in viscosity. The results indicate that the polymerized whey proteins may be an effective thickening agent to improve the consistency and syneresis of yogurt and other similar cultured dairy products.
Session 14A, Dairy Foods: General developments in dairy technology I
|