Structure and functional properties of active packaging films prepared by incorporating different flavonols into chitosan based matrix.

Kaempferol, quercetin and myricetin are typical flavonols that feature different number of hydroxyl substituents at B-ring. In this study, kaempferol, quercetin and myricetin were individually mixed with chitosan (CS) based film matrix to develop active packaging films. Results showed the incorporation of flavonols produced dense inner microstructure by establishing intermolecular hydrogen bonding interactions with film matrix. The addition of flavonols reduced the water vapor permeability, oxygen permeability and UV-vis light transmittance of the films, whereas elevated the tensile strength, elongation at break, 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity and antimicrobial activity of the films. Among all the films, the film containing myricetin showed the highest water vapor and oxygen barrier abilities and mechanical properties. Notably, different films presented distinct flavonol release behaviors in fatty and aqueous food stimulants. Kaempferol was easily released into fatty food stimulant, while myricetin was easily released into aqueous food stimulant. The release behavior of flavonols in different food stimulants greatly affected the antioxidant activity of the films. Our results suggest the structure and functional properties of the films are closely related to the number of hydroxyl substituents at B-ring of flavonols.