Effect of cinnamon essential oil nanoemulsion emulsified by OSA modified starch on the structure and properties of pullulan based films

Cinnamon essential oil (CEO) was emulsified by octenyl succinate anhydride (OSA) modified starch to make nanoemulsion, which was incorporated into pullulan solution to generate biodegradable films. The effects of emulsion on the physicochemical and antimicrobial properties of pullulan-based films were evaluated. Results showed that CEO nanoemulsion decreased the tensile strength, water content and water vapor permeability, while increased the elongation at break and antimicrobial properties of pullulan-based films. It was found that the composite film with 200 mL/L emulsion content (3 g/kg CEO), 30 g/kg OSA modified starch, and 10 min ultrasound treatment had the best overall properties. The treatment increased the thickness and elongation at break by 29% and 37%, respectively, while reduced the tensile strength and water content by 31% and 24% compared with control films. Meanwhile, this composite films inhibited growth of Staphylococcus aureus and Escherichia coli by 60% and 45%, respectively. The FTIR spectra indicated that the emulsion had good compatibility with pullulan films, which may be due to hydrogen bond formation between OSA modified starch and pullulan. Furthermore, CEO was evenly encapsulated in pullulan films, and OSA modified starch was able to enhance loading capacity of CEO in pullulan films to improve the antimicrobial activity.