Characterization and Antimicrobial Activity of Sweetpotato Starch-Based Edible Film Containing Origanum (Thymus capitatus) Oil

The objectives of this research were to characterize the mechanical and barrier properties of sweetpotato starch (SPS)-based film (SPSF) and to investigate the antimicrobial activity of SPSF containing origanum oil (OG) against foodborne pathogenic bacteria. The SPSF was fabricated with the SPS extracted from commercial sweetpotato roots. Tensile strength (TS), percent elongation at break (E), and water vapor permeability (WVP) were determined to characterize the SPSF fabricated with selected SPS concentrations, plasticizers, and the concentrations of plasticizers. The agar diffusion assay was used to determine the antimicrobial activity of SPSF containing selective concentrations of OG against Salmonella Enteritidis, Escherichia coli O157:H7, and Listeria monocytogenes. The SPSF fabricated with 2.5% SPS exhibited the greatest TS (4.58 MPa). The TS, E, and WVP of SPSF plasticized with 40% sorbitol exhibited 7.96 MPa, 77.92%, 0.212 ng m/m² S Pa, respectively. Therefore, the SPSF fabricated with 2.5% SPS and 40% sorbitol was determined as the optimum film. The antimicrobial activity of the SPSF containing OG increased as the concentration of OG increased. And the SPSF containing OG exhibited greater inhibitory effects against the gram-negative bacteria such as S. Enteritidis and E. coli O157:H7 than the gram-positive L. monocytogenes. The greatest antimicrobial activity was observed against S. Enteritidis when the SPSF containing 2% OG was applied, and the maximum square of zone width was 18.43 mm².