Processing Effects on Protein–Polysaccharide Biointerfaces in Omega-3 Microencapsulation: Linking Structure with Oxidative Stability and Gastrointestinal Functionality

Omega-3 polyunsaturated fatty acids (PUFAs) are widely recognized for their nutritional and health benefits, yet their high susceptibility to oxidative degradation remains a major challenge in the development of stable food-grade delivery systems. Protein–polysaccharide-based microencapsulation provides an effective strategy for protecting omega-3-rich oils while modulating their release and accessibility during gastrointestinal digestion. However, the relationships among processing conditions, wall-material composition, resulting structural organization, and functional performance remain insufficiently integrated, limiting the establishment of general design principles for omega-3 delivery systems. This review critically examines these relationships from a processing–structure–function perspective, with particular attention to molecular interactions, interfacial organization, matrix architecture, drying and coacervation processes, oxygen transport, lipid oxidation, and gastrointestinal transformations. The reviewed evidence indicates that encapsulation efficiency alone is insufficient to predict functional performance. Instead, oxidative stability arises from the combined effects of interfacial organization, surface-oil distribution, matrix continuity, and oxygen transport, while gastrointestinal functionality depends on structural transformations that regulate lipid release, bile-salt-mediated interfacial remodeling, lipase accessibility, and bioaccessibility. Importantly, increasing interfacial or matrix resistance can improve oxidative or gastric protection but may also restrict intestinal lipid digestion, revealing a structure-dependent trade-off between protection and digestive accessibility. Effective omega-3 delivery systems therefore require structures that provide sufficient protection during processing and storage while allowing controlled reorganization during gastrointestinal digestion. This processing–structure–function framework can support the rational selection of wall-material combinations and processing conditions for omega-3-fortified foods and functional ingredients.