Acid-induced gelation of milk protein concentrates with added pectin: Effect of casein micelle dissociation

Abstract

The dynamics of the formation of the acid gel network for mixtures of milk protein concentrate (MPC) and low methoxyl amidated (LMA) pectin were studied using rheological measurements. The results as a function of pectin content and casein micelle integrity, from neutral pH to approximately pH 4.2, together with the microstructural changes observed in some of these systems, are presented. The gelation profiles of a mixture of 4% w/v MPC and LMA pectin (0–0.075% w/v) after the addition of 1.2% w/v glucono- δ-lactone showed a gradual decrease in the shear modulus with the incorporation of pectin. The effects of casein micelle integrity on casein–pectin interactions were studied, by preparing MPC dispersions containing various levels of micellar casein. A gradual change in the shear modulus, from a disrupting effect of pectin added to MPC, in which the casein micelles are intact, to a clear synergistic effect of pectin added to dissociated casein systems, was found in the acid-induced milk gels.