Acid gelation functionality of casein micelles in concentrated state: Influence of calcium supplementation or chelation combined with enzymatic stabilization

Abstract

The main structure-building component in gelled dairy products is the casein micelle (CM). It was previously shown that in concentrated state of CMs, the changes of their compositional and colloidal properties in response to the addition or chelation of calcium divers from the reactions at milk-like casein concentration. This study aimed to evaluate the relationship between these specifically induced properties of CMs and the acid gelation functionality of a micellar casein concentrate (MCC). A covalent stabilization of the structures of pre-modified and native CMs by treatment with transglutaminase (Tgase) prior to acidification with glucono-δ-lactone was additionally tested. During acidification, structure formation was monitored in a rheometer to gain insights on mechanistic changes in the course of structural changes during acidification compared to gelation of unmodified MCC. Gelation pH, gel firmness, and serum binding capacity were analyzed to characterize gel structures at a final pH of 4.6. The structure formation process was highly affected by prior changes in composition, integrity, and structural stabilization of CMs. Gelation pH and acid gel firmness were reduced by ionic strength. Thermal and Tgase treatment induced opposing effects, leading to compensation when combined with prior salt supplementation. A synergistic increasing effect on serum binding capacity was found for trisodium-citrate supplementation and subsequent Tgase treatment. New mechanistic insights on acid gel structure formation progression were gained. This study provides a better insight into the relationship between structural CM properties prior to acid gelation and the resulting acidification progress, as well as the final acid gel properties.