Preparation of emulsions with resveratrol to form functional coatings: Effect on yellowing of frozen limes during storage

Radical mediated reaction method was chosen to prepare ferulic acid grafted pectin (FA-P) to enhance the properties of the native pectin. HPLC and FTIR results presented that ferulic acid was successfully grafted onto the pectin molecule. Among them, FA-P conjugation with a mass ratio of 0.75:1 was the most effective with the highest grafting efficiency, emulsifying activity index and emulsifying stability index. Subsequently, FA-P (0.75:1) was used to emulsify resveratrol to prepare FA-P-R emulsion. Compared to the resveratrol emulsion emulsified with native pectin (P-R), FA-P-R had a lower ζ-potential and a 57.4% reduction in mean particle diameter. Scanning electron microscopy demonstrated that the particles of FA-P-R emulsion were more rounded, with flatter and smoother surfaces, suggesting the formation of a better emulsified morphology. In addition, the encapsulation efficiency, load capacity and light stability of FA-P-R increased by 31.6%, 31.5% and 28.0%, respectively, compared to P-R. The FA-P-R samples showed the best antioxidant properties among the four emulsions of FA-P-R, P-R, FA-P and pectin for the functional coatings prepared, with the highest DPPH and ABTS⁺ radical scavenging activity. Finally, the FA-P-R functional coating for wrapping frozen limes was able to significantly inhibit the yellowing of frozen limes during freezing storage. The results highlight that the prepared FA-P-R functional coating can be used to inhibit the quality deterioration of frozen fruits and extend the freezing period.