Universality of in situ interfacial aldehyde-protein Schiff-based reaction in the construction of protein-stabilized emulsions: Formation, interfacial properties and digestion behavior

Application of dynamic imine chemical reaction between aldehydes and proteins at the interface has been reported to improve the properties of the interface layer and the stability of protein emulsions. Hence, in order to confirm the universality of in situ interfacial imine chemistry in the emulsion construction, 3 proteins and 7 aldehydes were systematically selected to investigate the effects of their molecular structures on the formation and stability of protein-stabilized emulsions. The digestion behavior of emulsions and protein hydrolysis were further evaluated. The results showed that all selected aldehydes improved the storage stability of emulsions to varying degrees, depending on the type of aldehyde and protein involved. Cinnamaldehyde and valeraldehyde emerged as the most effective among aroma aldehyde and linear fatty aldehyde, respectively, regarding to their hydrophobicity and conjugation effect. Taking whey protein and cinnamaldehyde as the example, cinnamaldehyde addition decreased the interfacial tension of whey protein and caused the solid-like interfacial layer due to their chemical interaction. Furthermore, acidic pH caused the increase of the interfacial tension between aldehyde and protein. After i n vitro simulated gastrointestinal digestion, C aco-2  cell experiments demonstrated that more peptides from the digesta of cinnamaldehyde-modified whey protein emulsion were transferred than those from the control emulsion. The research results confirm the application of in situ interfacial imine-chemistry as a novel strategy to improve the stability of protein-stabilized emulsions.