Tuning the structure and coagulation behaviour of artificial casein micelles by varying the casein composition

The casein composition of milk varies significantly within and between mammalian species, but its effect on the structure and (functional) properties of casein micelles is poorly understood. The preparation of artificial casein micelles (ACM) allows systematic variation of the casein composition, potentially enabling the design of functional ACM from a selection of casein fractions with customised properties. We prepared ACM from α_s- and κ-casein and β- and κ-casein in different ratios, as well as ACM from α_s-, β-, and κ-casein, and analysed their composition, size, hydration, and rennet coagulation behaviour. Our results demonstrate that ACM properties and coagulation vary significantly with casein composition. α_s-Caseins form dense and compact micelles yielding firm gels upon renneting, while β-casein forms loose, highly hydrated micelles resulting in softer gels. Varying the relative proportions of caseins affects micelle size and hydration and influences the gel strength. Higher proportions of κ-casein produce smaller ACM and firmer curds, while higher proportions of β-casein increase micelle hydration and decrease curd firmness. These findings enable the design of ACM with tailored properties from blends of casein fractions, providing valuable insights for food manufacturers and the precision fermentation industry to streamline the production of animal-free dairy alternatives.