An O/W antibacterial emulsion stabilized by protein-polyphenol complexes to control food spoilage: A study on whey protein and caffeic acid.

This study used a non-covalent complex of whey protein (WP) and caffeic acid (CA) as an interface-stabilizing agent. The interaction between WP and CA was analyzed through spectroscopy and molecular dynamics simulations. A Pickering emulsion (WC-PE) with oregano essential oil (OEO) was created using the WP-CA complex and characterized. This complex was then combined with sodium alginate (SA) to produce calcium alginate gel beads (WC-PE-CAB), which were tested for their ability to preserve shrimp freshness. FT-IR spectroscopy and molecular dynamics showed that CA mainly binds to β-lactoglobulin (β-LG) through hydrogen bonding, increasing α-helix content from 33.51% to 43.46% and decreasing random coil content from 13.42% to 8.69%, resulting in a looser but more ordered structure. The structural modifications moderately improved the thermal stability of the WP-CA complex at a moderate CA content, whereas excess CA reduced it. Its emulsifying activity increased from 7.30 m2/g to 12.86 m2/g, and antioxidant activity improved. Molecular simulations and fluorescence staining confirmed that WP-CA particles can adsorb at the oil-water interface, forming stable oil-in-water Pickering emulsions, with CA enhancing stability. Preservation experiments with fresh shrimp showed this system effectively delayed the increase of pH, total volatile basic nitrogen (TVB-N), and total viable count (TVC), extending shelf life by 12 to 36 h. This study provides a theoretical and practical basis for designing protein-polyphenol complex-stabilized Pickering emulsions for preservation.