Tailoring the structure of casein micelles through a multifactorial approach to manipulate rennet coagulation properties. (April 2020) - Lazzaro, Fanny
Abstract: The properties of casein micelles are known to be affected by modifications to the environment, such as variations in pH or the addition of salts, yet the scientific literature typically considers the effects of one factor at a time, while in industrial processes, several modifications are performed simultaneously. The aim of this study was to assess the impact of multifactorial environmental modifications on the colloidal, structural and rennet coagulation properties of casein micelles in a simplified model system. A key finding was that dense regions (~20 nm in size) could be released from the casein micelle. The addition of NaCl and CaCl2 had opposing effects, i.e. enhancing or limiting this micellar disruption, respectively. A decrease in pH had the strongest impact on the mineral balance, causing the colloidal CaP to solubilize and the micelle to swell. The rennet clotting time was impacted by variations in pH and NaCl content. Interestingly, a consideration of all three levels of casein micelle structure and their interactions was needed to explain variations in the firmness of rennet gels. This study illustrates the complex interplay of factors affecting micellar structure and improves our understanding of how micelles can be manipulated to control their properties. Graphical abstract: Image 1 Highlights: Rennet gel firmness is influenced by 3 levels of internal casein micelle structure. Rennet clotting time is principally influenced by variations in pH and NaCl. Addition of NaCl causes the release of the dense regions from the casein micelle. Addition of CaCl2 limits the release of the dense regions from the casein micelle. Decreasing pH solubilizes calcium phosphate and causes the casein micelle to swell.