Benzoyl chloride is commonly used as a food preservative to control microbial contamination by reducing the growth rate and maximum growth population and extending the lag period of the target microorganisms. Benzoyl chloride Was Successfully incorporated into a matrix of an ethylene acrylic acid polymer. The reaction of benzoyl chloride with ethylene acrylic acid was confirmed by Fourier transform infrared spectroscopy. The antimicrobial activity of modified ionomer films was studied through the monitoring of the growth of Penicillium sp. and Aspergillus sp. on the modified films. An untreated film did not show any inhibition of microbial growth. The inhibition activity was least in an ionomer film treated with acid and benzoyl chloride, and this was followed by a film treated with alkali and benzoyl chloride. The maximum inhibition was observed in a film treated just with benzoyl chloride. (c) 2006 Wiley Periodicals, Inc.