Gelation of mixed systems whey protein concentrate-gluten in acidic conditions

Gels of whey protein concentrate (WPC)-gluten were prepared by heating WPC-gluten dispersions (10% whey protein/0-5-10% gluten protein, w/w; pH 3.75 or 4.2). Gels were characterized through solubility assays in different extraction solutions, measures of water-holding capacity (WI-IC), firmness, elasticity and relaxation time, and light microscopy. Differential scanning calorimetry (DSC) of WPC-gluten dispersions was also performed. Gluten increases the firmness and elasticity of gels, mainly at pH 4.2. The WHC also increases with gluten content, being higher at pH 3.75 than at pH 4.2. Solubility assays indicate that electrostatic forces, hydrophobic and W bindings would be involved in maintaining the gel structure of WPC gels at pH 3.75 and 4.2, whereas in mixed gels of WPC-gluten, the principal forces responsible for the maintenance of the gel structure at these pHs would be hydrophobic and H bindings, and in gels prepared at pH 4.2 also disulfide bonds, but in a minor extent. The presence of gluten shifts the apparent transition temperature for whey protein denaturation towards lower temperatures. Gels with gluten present a smooth network with gaps and a more elastic appearance, as observed by light microscopy. (C) 2000 Elsevier Science Ltd. All rights reserved.