Hu_2026_Food.Res.Int_225_118063

To address the poor physicochemical stability of whey protein isolate (WPI)-stabilized emulsions, a novel chitooligosaccharide-caffeic acid covalent complexes (COS-CA) was first synthesized using lipase-catalyzed acylation to co-stabilized an O/W emulsion with WPI. Structural analyses confirmed that caffeic acid (CA) was successfully grafted onto the primary hydroxyl group of chitooligosaccharide (COS) through an ester bond, with a maximum grafting degree of 9.84 mg/g. Moreover, the WPI + COS-CA (physical mixture) exhibited stronger antioxidant activity than WPI alone or the WPI + COS (physical mixture), with DPPH radical scavenging, Fe(3+) reducing, and Fe(2+) chelating capacities of 94.42 %, 3.13 mM, and 58.26 %, respectively. In addition, the emulsifying activity index and emulsifying stability index of WPI + COS-CA were the highest (36.02 m(2)/g and 232.95 min). Subsequently, the emulsions stabilized by WPI, WPI + COS, and WPI + COS-CA were prepared. It was found that the WPI + COS-CA emulsion not only had an initial apparent viscosity 3 and 3.3 times higher than that of the WPI and WPI + COS emulsions, respectively, but also exhibited higher G' and G'' moduli and interfacial adsorbed protein content. Additionally, the WPI + COS-CA emulsion showed the lowest creaming index during storage and under environmental stresses. Moreover, this system significantly inhibited oxidation, reducing malondialdehyde by over 45 % and protein carbonyls by over 27 % after storage. Mechanism analysis indicated that COS-CA improved the stability of the WPI-stabilized emulsion by reinforcing interfacial strength and enhancing the antioxidant activity of WPI. This work proposes an innovative strategy for enhancing the physicochemical stability of WPI emulsion, which expands its potential applications in the food industry.