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Antibacterial activity of pullulan films containing thymol


Małgorzata Gniewosz, Department of Biotechnology, Microbiology and Food Evaluation, Warsaw University of Life Science, 02-776 Warsaw, Poland. E-mail:


Thymol displays strong activity against microorganisms that are of interest in clinical field and in food industry. Pullulan can form homogeneous films, which is an important property for its use as a coating material in the food industry. The present study determining the effect of thymol incorporated into a pullulan film against selected bacteria. The final content of thymol in the dried films ranged from 2.5 mg/cm2 to 52.9 mg/cm2. The structure of the surface and cross-section of the films were observed under a scanning electron microscope. The fruits were coated with a pullulan film, with thymol incorporated in the concentrations of 1.2, 1.5 and 3.0% and were evaluated for appearance and aroma. The pullulan films with thymol content ranging from 26.5 mg/cm2 to 52.9 mg/cm2 expressed strong inhibitory activity against the tested bacteria, compared with the pullulan films containing lesser concentration of thymol. The surface of the coated fruits was found to be shiny as compared with the non-coated fruits. Though the characteristic aroma of thymol was detectable it did evoke any undesirable sensory changes. Pullulan films containing thymol, which were effective against the tested bacteria, can be applied to extend the shelf life of packaged food products. Copyright © 2011 John Wiley & Sons, Ltd.