Physical Properties of Yogurt: A Comparison of Vat Versus Continuous Heating Systems of Milk

Abstract

Milk was processed by vat (85C for 10 to 40 min), high temperature, short time (98C for .5 to 1.87 min), and ultrahigh temperature (140C for 2 to 8 s) heating systems and made into yogurt. Yogurt firmness ranged from 90 to 104 g force for vat treatments, 74 to 96 g for high temperature, short time treatments, and 47 to 65 g for ultra-high temperature treatments. Planned contrasts between heating systems indicated significantly higher yogurt firmness and viscosity for vat versus high temperature, short time and ultra-high temperature systems. Yogurt from high temperature, short time milk showed the highest water-holding capacity, followed by ultra-high temperature and vat treatments. Correlation coefficient between yogurt firmness and whey protein denaturation was .83 and between apparent viscosity and whey protein denaturation was .89. Sensory evaluation indicated an overall preference for yogurt made from high temperature, short time (1.87 min) milk.