Protein-driven interfacial engineering shapes fat networks and mechanical resilience in frozen colloids

Proteins play a pivotal role in directing the interfacial assembly and hierarchical structuring of frozen colloidal systems, yet the mechanistic link between protein molecular architecture and macroscopic stability remains poorly understood. Here, we investigate how distinct dairy proteins—whey protein isolate (WPI), micellar casein concentrate (MCC), milk protein concentrate (MPC), and skim milk powder (SMP)—govern the formation of multiscale networks in lactose-free frozen aerated emulsions under low-shear freezing. The structure and flexibility of proteins regulated the relationship between interfacial packing and the mechanical strength of the surrounding network. Samples with limited interfacial coverage (WPI, SMP) stabilized the emulsions through the formation of pervasive, fat-coalesced networks, whereas casein-rich samples (MCC, MPC) relied on cohesive, protein-dense matrices, with macroscopic melting resistance dictated by the large-deformation resilience of the fat network rather than bulk viscosity. Microstructural analysis confirmed that the protein-governed fat architecture templates air-bubble organization and constrains ice crystallization, establishing a multiscale hierarchy that underpins structural integrity. These findings reveal protein-driven interfacial engineering as a dominant mechanism controlling network formation and stability, providing a mechanistic framework for designing next-generation, clean-label, high-protein frozen desserts.