RHEOLOGICAL ANALYSIS OF ANION-INDUCED MATRIX TRANSFORMATIONS IN THERMALLY-INDUCED WHEY-PROTEIN ISOLATE GELS

The formation of thermally induced whey protein isolate (WPI) gels exhibiting fine-stranded, mixed and particulate matrices was investigated. Various concentrations of stabilizing salts (sodium sulfate and sodium phosphate) or a chaotropic salt (sodium thiocyanate) were used to form the different types of thermally induced gel matrices. Gelation under all conditions showed similar trends in small-strain viscoelastic properties. Storage modulus (G') increased during heating to and hold at 80 degrees C followed by an additional increase in cooling to 25 degrees C. Mixed matrix gels had proportionately more hydrophobic interactions (large Delta G'(heat)/Delta G'(cool)) and had greater initial gelation rates than fine-stranded and particulate matrix gels. The proportion of hydrophobic interactions in the gels correlated with the anions' influences on the hydrophobic effect as indicated by their positions in the Hofmeister series.