Preparation and characterization of active oxidized starch films containing licorice residue extracts and its potential against methicillin-resistant S. aureus.

The antibacterial and antioxidant packaging films were fabricated by incorporating licorice residue extracts (LREs) into oxidized starch (OS) films. The bioactive fraction (BF) was firstly obtained from LREs by using bioassay-guided isolation method. The BF showed potent anti-Gram(+) bacteria effects, especially against methicillin-resistant S. aureus (MRSA) with MIC of 32.5 μg/mL. The present results also indicated that the addition of BF could significantly decrease the moisture content, water vapor permeability, light transmittance of OS films. Notably, the antibacterial and antioxidant activities of OS films significantly enhanced with the concentration of BF increasing. Moreover, the films with the highest concentration of BF showed the lowest tensile strength (4.23 MPa) and the highest elongation at break (63.89%). Meanwhile, the bioactive films could release bioactive compounds such as licochalcone A and licochalcone B into the alcoholic and fatty food simulants. Taken together, the active OS films containing LREs have the potential for application in food packaging films, due to its potential against MRSA and antioxidant activity as well as good physicochemical properties.