Gelation of casein-whey mixtures: effects of heating whey proteins alone or in the presence of casein micelles

Abstract

The aim of the present work was to investigate the role of whey protein denaturation on the acid induced gelation of casein. This was studied by determining the effect of whey protein denaturation both in the presence and absence of casein micelles. The study showed that milk gelation kinetics and gel properties are greatly influenced by the heat treatment sequence. When the whey proteins are denatured separately and subsequently added to casein micelles, acid-induced gelation occurs more rapidly and leads to gels with a more particulated microstructure than gels made from co-heated systems. The gels resulting from heat-treatment of a mixture of pre-denatured whey protein with casein micelles are heterogeneous in nature due to particulates formed from casein micelles which are complexed with denatured whey proteins and also from separate whey protein aggregates. Whey proteins thus offer an opportunity not only to control casein gelation but also to control the level of syneresis, which can occur.

Role of Whey Protein-Casein Complexes on Yoghurt Texture

“…However, Schorsch et al (2001) and Donato et al (2007a) increasing the final firmness and also inducing the formation of acid gels. Regarding the role of micelle bound whey protein, Schorsch et al (2001) applied heat treatment on the unheated casein micelles in the presence of soluble denatured whey protein/ -casein complexes to increase the micelle bound complexes and consequently noticed a firmer gel as well as uniformity of the acid gel.…”

“…Conflicting results were observed on the relative role of micelle bound whey protein and the soluble denatured whey protein/ -casein complexes on the properties of acid gels (Lucey et al, 1998b, Guyomarc h et al, 2003aAnema, 2004). Some reports point out that there is an important role of micelle bound whey proteins on the yoghurt texture (Lucey et al, 1998b;Schorsch et al, 2001), whereas other reports have highlighted on the significant role of the soluble denatured whey protein/ -casein complexes (Anema, 2004;Rodriguez and Dalgleish, 2006). Generally, the micelle bound whey protein and/or the soluble denatured whey protein/ -casein complexes modify the firmness, water holding capacity, whey separation, rheological and microstructural properties of the yoghurt gels.…”

“…Regarding the role of micelle bound whey protein, Schorsch et al (2001) applied heat treatment on the unheated casein micelles in the presence of soluble denatured whey protein/ -casein complexes to increase the micelle bound complexes and consequently noticed a firmer gel as well as uniformity of the acid gel. In fact, whey protein-casein micelles induce the lowering syneresis by hindering fusion of aggregated casein micelles or increase water holding capacity due to the high water binding capacity of the unfolded whey proteins (Puvanenthira et al, 2002).…”

“…On the contrary, some researchers (Schorsch et al, 2001;Ozcan et al, 2015) observed the effect of the micelle bound complexes and the soluble denatured whey protein/ -casein complexes on the mechanical and structural properties of the yoghurt curd by altering the initial conditions of the milk prior to heat treatment. Some studies focused on the micelle bound complexes by lowering the milk pH below the natural pH (~ 6.7) of milk (Anema and Li, 2003;Lakemond and van Vliet, 2008), which played a significant role on the final elastic properties of acid milk (Lucey et al, 1998b;Schorsch et al, 2001).…”

“…Some studies focused on the micelle bound complexes by lowering the milk pH below the natural pH (~ 6.7) of milk (Anema and Li, 2003;Lakemond and van Vliet, 2008), which played a significant role on the final elastic properties of acid milk (Lucey et al, 1998b;Schorsch et al, 2001). Despite the role of the micelle bound complexes, other studies emphasized the important role of the soluble denatured whey protein/ -casein complexes on the structural properties of acid gels.…”