Sustained-release antimicrobial gelatin film: Effect of chia mucilage on physicochemical and antimicrobial properties

Essential oil-loaded edible films usually suffer from short-term antimicrobial effects due to the fast evaporation rate of essential oils during film preparation and storage process. The oregano essential oils (OEOs) loaded chia mucilage/gelatin (CM/G) blended films were prepared with the aim of alleviating the evaporation rate of essential oils and achieving active films with prolonged antimicrobial properties. When chia mucilage (CM), as a new potential source of polysaccharide gum, was incorporated into gelatin film forming solution, the decrease in tensile strength (TS), water vapor permeability (WVP) accompanied with the increase in elongation at break and water contact angle were observed. Antimicrobial effect evaluation revealed that gelatin films added with CM achieved long-term antimicrobial effects against both gram-positive and gram-negative bacteria. Surface and cross-section morphologies observed via SEM indicated that the addition of CM reduced the floating of essential oils in film. Rheological and FTIR measurements revealed that the observed higher retention rate of OEOs in film matrix was achieved by increasing the floating resistance during film forming process, inducing hydrogen bond interaction among film components. The release of OEOs evaluated by gas chromatography confirmed that the sustained antimicrobial activity exerted by CM/G films was due to the higher contents of OEOs retained during the preparation and storage processes. The present work offers an easy to perform formula in engineering essential oil loaded edible films with prolonged antimicrobial property, which is useful in the field of active films.