Development of antioxidant, antimicrobial and ammonia-sensitive films based on quaternary ammonium chitosan, polyvinyl alcohol and betalains-rich cactus pears (Opuntia ficus-indica) extract

Cactus pears (Opuntia ficus-indica) are rich in betalains, which are water-soluble nitrogenous pigments. This study aimed to develop antioxidant, antimicrobial and ammonia-sensitive packaging films by adding cactus pears extract (CPE) into quaternary ammonium chitosan (QAC)/polyvinyl alcohol (PVA) blend. The impact of CPE addition on the structure, physical and functional characteristics of the film was determined. Scanning electron microscopy revealed 1 wt% of CPE was compatible with film matrix, resulting in the most uniform and smoothest cross-sectional morphology. Fourier transform infrared and X-ray diffraction analysis demonstrated CPE interacted with film matrix via hydrogen bonding interactions. The addition of 1 wt%, 2 wt% and 3 wt% of CPE greatly enhanced the UV–vis light barrier, elongation-at-break, and antioxidant, antimicrobial and ammonia-sensitive properties of QAC/PVA films. However, only 1 wt% and 2 wt% of CPE addition increased water vapor barrier property and tensile strength of QAC/PVA films. The color of QAC/PVA films containing 2 and 3 wt% of CPE changed from purple to orange when shrimp was not fresh. Our results suggested QAC/PVA films containing CPE could be used as food packing materials in the future.