Antimicrobial activity and characteristics of edible films incorporated with Phayom wood (Shorea tolura) extract

The antimicrobial effect against Escherichia coli O175:H7, Staphylococcus aureus and Listeria monocytogenes of edible film containing phayom wood (Shorea tolura) extract was investigated. In this study, the minimum bactericidal concentration (MBC) of phayom wood (Shorea tolura) extract was established as 300 mg/L at which bacterial growth was completely inhibited. Antimicrobial properties of hydroxylpropyl methyl cellulose (HPMC) films containing 1-5 folds of MBC of phayom wood extract were tested. The edible films containing phayom wood extract exhibited more effective impact on the growth of L. monocytogenes than S. aureus and E. coli (p 0.05). The use of phayom wood extract at 1 fold of MBC incorporated into edible HPMC films did not exhibit any antimicrobial activity. However, the inhibitory effect of edible HPMC films containing phayom wood extract was observed only at 3, 4 and 5 folds of MBC. The greatest zone of inhibition was observed at 5 folds of MBC incorporated in edible HPMC films. Tensile strength and elongation at break significantly decreased with incorporation of phayom wood extract concomitantly with increased in water vapor permeability and films solubility. The color of edible films was affected by the addition of phayom wood extract; the results showed that increasing phayom wood extract yielded darker and more red-yellowish of resulted films. A lower transparency of the edible films was observed when a greater amount of phayom wood extract was incorporated (p 0.05). Phayom wood extract incorporated in edible films provided the films with a rougher surface than pure edible films.