14A-12 |
Influence of sulfonation on the properties of whey proteins |
D. P. TAYLOR, C. E. Carpenter, and M. K. Walsh. Dept. of Nutrition & Food Sciences, Utah State Univ., UMC 8700, Logan, UT 84322-8700 When extruding high concentrations of whey protein, it is beneficial if the protein is unfolded and soluble while in the extruder barrel. We hypothesize that sulfonation, which breaks disulfide bonds and adds negative charges to proteins, may increase the level of unfolded and soluble protein. The objective was to determine the effect of sulfonation on thermal denaturation temperatures and high temperature solubility of whey protein concentrate. Fresh whey was concentrated and sulfonated to levels ranging from 0 to 90% before freeze-drying. Denaturation onset temperature (To) and maximum peak temperature (Tmax) were measured with differential scanning calorimetry. High temperature solubility was measured with whey-starch mixtures heated (145 C for 10 minutes) in a solvent (0.2 M NaOH or water). After heating, the blend was dissolved overnight in a solution containing 1% of both SDS and B-mercaptoethanol. Samples were centrifuged, filtered, and protein in the filtrate was measured with a modified Lowry assay. Sulfonation decreased both To and Tmax of the beta-Lg fraction in the samples sulfonated to 72-74% compared to the control (0% sulfonation). While To of the alpha-Lb fraction did not significantly change between samples, Tmax of the alpha-Lb fraction decreased in samples sulfonated to 71% compared to those sulfonated to 20%. The endothermic event of beta-Lg seen at 130 C was also affected by sulfonation. Both To and Tmax decreased in the sample sulfonated to 79% compared to the control. For high temperature solubility, analysis showed that using NaOH compared to water increased the amount of soluble protein in samples with lower degrees of sulfonation but had less effect as percent sulfonation increased. Sulfonation changes the denaturation temperatures and high temperature solubility of whey protein. These changes may enable whey to be successfully extruded at lower temperatures or at higher concentrations.
Session 14A, Dairy Foods: General developments in dairy technology I
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