Effects of Litsea cubeba essential oil nanoemulsion on physical properties and antimicrobial activity of konjac glucomannan/sodium alginate composite films

A novel antimicrobial composite film was prepared from konjac glucomannan (KGM)/sodium alginate (SA) incorporating Litsea cubeba essential oil (LCEO) nanoemulsion. The effects of oil droplet size and content on the structural, mechanical, barrier and antimicrobial properties of the films as well as the retention and release of LCEO were investigated. Results showed that with increasing LCEO content, the oil droplets became larger but well-distributed and their interference with the ordered entangled network of KGM/SA molecules increased. The incorporation of LCEO enhanced the film’s elongation at break (≈ 36.5%), water contact angle (≈ 121%), water vapor barrier (≈ 31.6%), UV shielding, opacity (from 3.15 to 11.12), and antimicrobial properties. The films with high LCEO content had high LCEO retention, with LCEO being released slowly but continuously. After 35 days of storage at 25 °C, the films showed a maximum retention of 56.21% of LCEO and displayed a long-lasting inhibition against Escherichia coli and Staphylococcus aureus with zones of inhibition of 10.93 mm and 9.80 mm in diameter, respectively. At the same LCEO content, smaller oil droplets resulted in a denser film structure with better physical and antimicrobial properties. The developed KSM/GA composite films were promising as a potential antimicrobial material for food packaging with sustained release characteristics.