Biofunctional Interfaces for Sustainable Emulsions: Insights from Microalgae-Copepod Nutrition and SCFA-Starch Pickering Systems

Sustainable emulsions rely on interfacial materials that are efficient, suitable for food applications, and environmentally friendly. This review connects two distinct but complementary areas: (1) the trophic interaction between microalgae and copepods in aquaculture live-feed systems, and (2) the use of short-chain fatty acid (SCFA)-modified starch particles as Pickering stabilisers. This study investigates the influence of molecular and colloidal factors, including adsorption, viscoelastic film formation, wettability, and digestion-triggered disassembly, on emulsion stability and functionality. In microalgae-copepod systems, cell-wall polysaccharides, membrane glycolipids, phospholipids, proteins, and extracellular polymers provide amphiphilic motifs and steric-electrostatic barriers that function as bioemulsifiers. In SCFA-starch systems, esterification and inclusion complexation modify particle hydrophobicity and contact angle, resulting in recyclable interfacial armour that provides additional nutritional benefits via SCFA release. This study examines the relationships between structure and function, methods for interfacial characterisation, stability during processing and digestion, and sustainability metrics, including circular bioeconomy approaches that enhance the value of algal residues and fermentation-derived short-chain fatty acids (SCFAs). We propose design rules for clean-label, digestion-responsive emulsions suitable for food applications, nutraceutical delivery, and aquaculture feed oils. The integration of these two platforms reveals opportunities for the development of scalable, low-impact biofunctional emulsions.