Upcycling tea residue into plant-based emulsifiers via enzymatic polysaccharide degradation and protein structural modulation

Tea residue, a tea processing by-product, yields alkaline-extracted proteins with limited emulsifying capacity due to strong interactions with polysaccharides such as pectin and cellulose. A polysaccharide-targeted enzymatic strategy was developed by systematically comparing carbohydrases, proteases, and transglutaminase (TG). Selected carbohydrases (Viscozyme® L, pectinase, cellulase) effectively disrupted protein–polysaccharide complexes, enhancing the emulsifying activity index (EAI) by 2.4-fold compared to untreated controls ( P < 0.05), and significantly outperforming proteases and TG. Mechanistic analysis showed that polysaccharide degradation reduced ionic and hydrogen bonding (>90%), exposed hydrophobic groups (220% increase in free sulfhydryl), and promoted β-sheet formation (up to 56%), facilitating dense interfacial film formation. Dialysis experiments revealed that removing small peptides and pectin fragments (<3 kDa) increased α-helix content (to 27%) but impaired emulsification, while retention of oligosaccharides improved stability via viscosity and steric hindrance. This enzymatic approach offers a sustainable and structure-guided pathway to convert food processing waste into clean-label, plant-based emulsifiers, contributing to the functional valorization of agro-industrial by-products.