Oregano essential oil loaded soybean polysaccharide films: Effect of Pickering type immobilization on physical and antimicrobial properties

Abstract Essential oil-loaded edible films usually suffer from short-term antimicrobial effects due to the uncontrolled evaporation of essential oils during film preparation and storage. A novel approach was developed to fabricate soluble soybean polysaccharide (SSPS)-based films that incorporated oregano essential oil (OEO) as antimicrobial agent. OEO was first encapsulated in a Pickering emulsion stabilized by complex coacervates of acid soluble soy protein (ASSP) and SSPS. Films were then prepared by incorporating the Pickering emulsions into SSPS solutions, where octenyl succinic anhydride (OSA) was used as the esterifying agent for interfacial and bulk SSPS. Incorporation of Pickering emulsion led to the decrease in transparency and tensile strength of films as the loading percentage increased. The surface and cross-sectional morphological observation revealed that OEO droplets distributed well in film matrix with evident internal cavities in films. The ASSP/SSPS complexes interface avoided flocculation and coalescence among OEO droplets, and the esterification reaction between SSPS and OSA reinforced the interfacial layer and the continuous phase. The immobilization effect held more essential oils within the film matrix during film preparation and showed prolonged antimicrobial property against three selected pathogenic bacteria.