The Casein Micelle: Stability And Heat Induced Interactions

The increasing availability of micellar casein obtained by membrane separation creates a need to better understand the effect of processing conditions, on the stability and properties of this ingredient. This work focused on studying the heat-induced interactions in micellar casein concentrates, and in micellar casein (MCN)-soy protein (SP) blends. These changes were investigated using a range of physical measurements (zeta potential and particle size measurements, rheological analyses) and chemical analyses (compositional, differential solubility and Native-PAGE analyses). First, heat induced effects on the properties of micellar casein (MCN)-soy protein (SP) blends (1:1 ratio) were evaluated. Individual and mixed protein systems of 2.5% - 15% concentration were subjected to temperatures between 40[MASCULINE ORDINAL INDICATOR]C - 95[MASCULINE ORDINAL INDICATOR]C. Heat treatments at T[GREATER-THAN OR EQUAL TO]80[MASCULINE ORDINAL INDICATOR]C induced soy protein (glycinin) denaturation, which resulted in protein aggregation and network formation by disulfide bonding, when soy protein content >6.3%. There was no evidence of cross-linking between soy proteins and casein micelles, as disulfide bonding seemed to occur exclusively between soy protein molecules. In MCN-SP mixtures with soy protein content