pH-sensitive intelligent packaging films from Kodo millet (Paspalum scrobiculatum) starch and gum tragacanth incorporated with beetroot peel extract for monitoring shrimp freshness

Abstract

This study aims to develop intelligent pH-sensitive food packaging films based on kodo millet starch (KMS), gum tragacanth (GT), and zinc oxide nanoparticles (ZNP) incorporated with betalain-rich beetroot (Beta vulgaris L.) peel extract (BPE). The physical, mechanical, optical, microstructural, thermal, barrier, and functional properties of films with different BPE concentrations (50, 100, and 200 % of dry matter weight) were studied. The results proved betalain to be the major component in the BPE, which showed significant color change under alkaline conditions. Field emission scanning electron microscopy demonstrated good compatibility among the film constituents. Fourier transform infrared spectroscopy suggested hydrogen bonding interactions between the betalain-BPE and KMS/GT/ZNP-based film matrix. Incorporating the extract at different concentrations enhanced the ultraviolet-visible light barrier, antioxidant properties, and antimicrobial properties. The betalain-rich films showed color variation from pink in an acidic medium to yellow in an alkaline medium. The film with a 200 % concentration of BPE represented the highest color change when exposed to ammonia compared to other films. During the freshness indicator study of shrimp, the total volatile basic nitrogen concentration increased. The film with a 200 % concentration of betalain extract showed visible color changes from pink to pale yellow. Overall, our results suggest that the film containing a 200 % extract concentration can be used as an active pH-responsive packaging in the food industry.