EFFECTS OF ANIONS ON THERMALLY-INDUCED WHEY-PROTEIN ISOLATE GELS

Fundamental fracture, water-holding and microstructural properties of thermally induced whey protein isolate gels containing one of two diva lent, stabilizing anions (sulfate and phosphate) or one monovalent, ch aotropic anion (thiocyanate) were investigated. All of the salts produ ced similar overall trends in stress and strain; however, transition p oints were salt specific. At ionic strengths 0.09 less than or equal t o mu less than or equal to 0.50, Na2SO4 and NaSCN produced strain valu es of very similar magnitudes. At low salt concentrations, gel matrice s were fine-stranded and hem water well. As salt concentrations increa sed gel matrices became particulate and water-holding capacities decre ased. Promotion of the particulate matrix formation folio wed the Hofm eister series (SO42- > HPO42- >>> SCN-). The calcium chelating ability of phosphate was responsible for inhibiting particulate matrix format ion. Optical density trends, reflecting stabilizing or chaotropic prop erties of each anion, indicated that differences between sulfate- and phosphate-containing gels could not be explained by Hofmeister-type st abilizing propensity.