Comparison of the structural, physical and functional properties of κ-carrageenan films incorporated with pomegranate flesh and peel extracts

In this study, active and intelligent packaging films were developed by incorporating polypheol-rich pomegranate flesh extract (PFE) or pomegranate peel extract (PPE) into κ-carrageenan matrix. The structural, physical, pH-sensitive, antioxidant and antimicrobial properties of κ-carrageenan-PFE and κ-carrageenan-PPE films were compared for the first time. Results showed PFE was composed of cyanidin-3-O-glucoside (49.76%), peonidin-3-O-(6-malon)-glucoside (9.61%), malvidin-3-O-(6-acetyl)-glucoside (14.89%), pelargonidin-3-O- (6″-ethylmalonyl)-glucoside (7.05%), pelargonidin-3-O-(6-acetyl)-glucoside (9.51%) and isorhamnetin (9.18%). PPE was mainly composed of gallic acid (15.73%), malvidin-3-O-(6-acetyl)-glucoside (4.07%), epicatechin gallate (3.66%), luteolin (5.69%), vanillic acid (7.82%), caffeic acid (4.37%), punicalagin (39.96%) and ellagic acid (18.70%). The tensile strength, water vapor and UV light barrier ability of κ-carrageenan film were significantly promoted by the incorporation of PFE or PPE. Due to different polyphenolic compositions, κ-carrageenan-PPE films possessed higher UV light barrier, antioxidant and antimicrobial properties than κ-carrageenan-PFE films at the same extract incorporation levels. Nonetheless, κ-carrageenan-PFE films exhibited pH-sensitive property because of abundant anthocyanins in PFE. Notably, the physical and functional properties of κ-carrageenan-PFE and κ-carrageenan-PPE films were closely related to the content of extract. Our results suggested κ-carrageenan-PFE films could be further used as active and intelligent packaging, whereas κ-carrageenan-PPE films could be explored as active packaging in food industry.