Beverage cloud stability with isolated soy protein

The purpose of this study was to optimise the use of isolated soy protein (ISP) as a clouding agent for beverages. ISP was fractionated by hydrophobic interaction chromatography (HIC) using 2 M KCl in a step gradient manner. A hydrophilic and a hydrophobic fraction were collected. The proteins therein were separated by SDS-PAGe. Each fraction was combined with citrus pectin in nine different ratios at pH 3.7 and subjected to cloud stability and turbidity studies for 28 days at 4 degrees C. The molecular weight patterns of the two fractions were different, indicating separation in the HIC column. Analysis of variance with repeated measures found no significant difference in cloud stability between the two fractions (P < 0.05). Empirically, the hydrophilic fraction acted as a better clouding agent. Significant differences in cloud stability and cloud turbidity were found between different ratios of pectin:protein (P < 0.05). No correlation was found between the initial cloud composition and cloud stability. Hydrophilic fraction in pectin:protein ratios 1:2 and 4:1 gave optimum cloud stability. This study reiterated the usefulness of ISP as a clouding agent. (C) 1998 Society of Chemical Industry.