Whey protein isolate/flavor cinnamaldehyde conjugates prepared by different methods and the stabilization effects on β-carotene-loaded emulsions

Whey protein isolate (WPI) interacts with cinnamaldehyde (CA) to form conjugates with superior functional properties, which are affected by the conjugate structures formed by different food processing techniques, especially heating treatment. Initially, we compared three preparation methods of conjugates, including heating WPI before interacting with CA [(HWPI)/CA)], heating the resulting conjugates without heating WPI initially [H(WPI/CA)], and the normal conjugates without any heating process (WPI/CA). Subsequently, these conjugates were used to stabilize emulsions for the encapsulation and delivery of 13-carotene. Both the aforementioned heating methods increased the interaction and enhanced the conjugates' surface hydrophobicity. Synchronous fluorescence suggested that heating expanded the protein structure and exposed hydrophobic groups, while higher CA concentration had a shielding effect on this process. Moreover, H-(WPI/CA) conjugates reduced the interfacial tension to 4.38 mN/m, resulting in the best emulsification, which effectively stabilized emulsions and protected 13-carotene from the influence of temperature. H-(WPI/CA) conjugates helped to maintain the retention rate at more than 70% within 28 days and improved 13-carotene bioaccessibility during digestion. This knowledge provides insights into investigating the relationship between conjugates preparation methods and their properties, and is of great significance for developing a novel multifunctional food ingredient system based on protein modification.