Development of multifunctional food packaging by incorporating betalains from vegetable amaranth (Amaranthus tricolor L.) into quaternary ammonium chitosan/fish gelatin blend films

Multifunctional food packaging was prepared by incorporating betalains-rich vegetable amaranth (Amaranthus tricolor L.) extract into quaternary ammonium chitosan (QC)/fish gelatin (FG) blend films. The structures, physical and functional properties of the films with and without amaranth extract (AE) were determined. Results showed betalains-rich AE was pH-sensitive and could change its colors under alkaline conditions. Structural characterization revealed the interactions between AE and film matrix were based on hydrogen bonds, which influenced the compactness of the films. Notably, AE significantly enhanced the thickness (from 0.076 to 0.089 mm), UV–vis light barrier ability, elongation at break (from 66.7% to 88.8%), 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity (from 6.8% to 95.8% at 5 mg/mL), antimicrobial activity against four foodborne pathogens (Escherichia coli, Staphylococcus aureus, Salmonella typhimurium and Listeria monocytogenes) and ammonia sensitivity of the films. However, AE remarkably reduced the water vapor permeability (from 34.9 × 10−11 to 26.4 × 10−11 g m−1 s−1 Pa−1) of the films. Notably, the films containing 5 wt% and 10 wt% of AE were suitable to monitor the freshness of shrimp. Our results suggested QC/FG films with betalains-rich AE could be used as antioxidant, antimicrobial and intelligent packaging in food industry. •Amaranth extract was added into quaternary ammonium chitosan/fish gelatin films.•Amaranth extract was rich in betalains and was sensitive to alkaline environments.•Amaranth extract enhanced the water vapor and light barrier properties of the films.•Amaranth extract improved antioxidant and antimicrobial activities of the films.•Films containing amaranth extract could be used to monitor shrimp freshness.