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The colloidal complexes composed of grape seed proanthocyanidin (GSP) and gelatin (GLT), as natural antioxidants to improve stability and inhibit lipid oxidation in menhaden fish oil emulsions, were evaluated. The interactions between GSP and GLT, and the chemical structures of GSP/GLT self-assembled colloidal complexes, were characterized by isothermal titration calorimetry (ITC), circular dichroism (CD), and Fourier transform infrared spectroscopic (FTIR) studies. Fish oil was emulsified with GLT to obtain an oil-in-water (o/w) emulsion. After formation of the emulsion, GLT was fixed by GSP to obtain the GSP/GLT colloidal complexes stabilized fish oil emulsion. Menhaden oil emulsified by GSP/GLT(0.4 wt %) colloidal complexes yielded an emulsion with smaller particles and higher emulsion stability as compared to its GLT emulsified counterpart. The GSP/GLT colloidal complexes inhibited the lipid oxidation in fish oil emulsions more effectively than free GLT because the emulsified fish oil was surrounded by the antioxidant GSP/GLT colloidal complexes. The digestion rate of the fish oil emulsified with the GSP/GLT colloidal complexes was reduced as compared to that emulsified with free GLT. The extent of free fatty acids released from the GSP/GLT complexes stabilized fish oil emulsions was 63.3% under simulated digestion condition, indicating that the fish oil emulsion was considerably hydrolyzed with lipase.