Formulation of heat- and acid-induced milk gels – Effect on texture, microstructure, and water distribution

Full-fat milk was fortified with 0.5, 1, 1.5, or 2 % whey protein isolate (WPI) or micellar casein isolate (MCI). The effect of protein addition on composition, microstructure, and physicochemical properties of heat- and acid-induced milk gels was assessed. Lower moisture and higher calcium content was observed in gels with higher amount of MCI compared with WPI. Low-field nuclear magnetic resonance showed that the population with shorter relaxation, assigned to casein micelles and a more dense protein network, may explain the hardest texture of MCI gels. Contrarily, WPI rich gels showed longer relaxation times which is in agreement with a more open and porous microstructure. Increasing the casein content by 0.5 % formed gel significantly harder, while adding 2 % WPI produced more inhomogeneous gels but the texture was not significantly affected compared with native milk. Protein formulation of the milk can modulate the textural and water holding properties of heat- and acid-induced milk gels.