Collagen peptides induce hollow vesicle formation during intestinal digestion to enhance curcumin bioaccessibility in whey protein concentrate-stabilized emulsions
Collagen peptide (CP) and whey protein are common ingredients in protein-rich functional beverages. However, their synergistic effects on digestion dynamics and nutraceutical bioaccessibility remain insufficiently elucidated. We here investigated how CP modulated the digestive fate, and curcumin bioaccessibility of whey protein concentrate (WPC)-stabilized emulsions. CP incorporation exhibited minimal influence on the initial physicochemical stability, droplet characteristics, or curcumin encapsulation efficiency (>88%). However, in vitro gastrointestinal digestion revealed that CP significantly increased curcumin bioaccessibility by 1.07- to 1.19-fold and accelerated the proteolysis of WPC-emulsified droplets. Microstructural analysis of the intestinal digesta demonstrated that CP induced the formation of distinct hollow vesicle-like structures, which were absent in the control emulsions. The soluble fraction of the digesta from CP-supplemented systems showed enhanced oleic acid solubilization in a dose-dependent manner, strongly associating with the formation of these hollow vesicular assemblies. Together, these findings indicate that CP modulates intestinal colloidal structures, thereby improving curcumin bioaccessibility.