Preparation, characterization and application of smart packaging films based on locust bean gum/polyvinyl alcohol blend and betacyanins from cockscomb (Celosia cristata L.) flower.

Cockscomb (Celosia cristata L.) is an edible and ornamental plant rich in natural pigments of betacyanins. In this study, smart packaging films were developed based on locust bean gum (LBG), polyvinyl alcohol (PVA) and betacyanins from cockscomb flower. Effect of cockscomb flower extract content (4 wt%, 8 wt% and 12 wt%) on the structural, physical and functional properties of LBG/PVA blend films was investigated. The addition of cockscomb flower extract elevated the immiscibility between LBG and PVA. Cockscomb flower extract interacted with LBG and PVA through hydrogen bonds, resulting in reduced film crystallinity. The film containing 8 wt% of cockscomb flower extract showed the lowest water vapor permeability (10.34 × 10-11 g m-1 s-1 Pa-1) and the highest tensile strength (23.63 MPa). The film containing 12 wt% cockscomb flower extract exhibited the lowest light transmittance and the highest elongation at break (41.12%) and antioxidant activity. Cockscomb flower extract made the films become reddish-purple and endowed the films with pH-sensitivity and ammonia-sensitivity. The films containing cockscomb flower extract showed obvious color changes from reddish-purple to brown/yellow when shrimp spoiled. Our results suggested LBG/PVA blend films with cockscomb flower extract were suitable smart packaging films for indicating shrimp freshness.