Use of antimicrobials in edible films requires knowledge of properties, environment.

Edible films and coatings are used for many important functions, such as to prevent physical damage to a product, to protect a product from oxidation or changes in its moisture content, and to enhance its appearance. By incorporating antimicrobials, the functionality of edible films and coatings can be extended to protect food from microbial spoilage and to extend its shelf life.

With many different edible films and types of antimicrobials commercially available, edible antimicrobial films can be engineered for almost any product. Because foods are so complex, several factors influence the type of film and coating material that would function best on a product. These factors include a product's intrinsic properties--pH, water activity and composition--as well as extrinsic issues such as temperature and relative humidity encountered during processing and storage.

Films and coating materials used currently in a variety of applications include: lipids (oil, waxes and emulsions); resins (shellac and rosin); carbohydrates (celluloses, pectins, chitin, starches and gums); and proteins (milk, soy, collagen, gelatin, wheat, corn and peanut). Additionally, plasticizers, emulsifiers or surfactants may be added to enhance the film or coating.

In choosing an antimicrobial, your primary consideration must be how effective it would be against the target microorganism. Antimicrobial interactions with the film material, food and environment must also be considered. Current antimicrobials include: organic acids (acetic, benzoic, lactic, proprionic and sorbic acids); fatty acids; parabens; bacteriocins (nisin); sulfites; sucrose esters; and other natural antimicrobials, such as natamycin and lysozyme.

For an antimicrobial film or coating to do an effective job, you must determine its antimicrobial effectiveness in the specific application; how extensively the antimicrobial migrates into the product; how well the film adheres to the product; and how it interacts with the product. You must also use a reasonable application procedure. Evaluating these requirements is key to successfully developing an effective antimicrobial film.

There are so many options available in terms of the types of coatings and antimicrobials that can be used. With a greater understanding of film and coating properties, edible antimicrobial films and coatings could be effectively engineered for any food product.

Further information. John Krochta, Department of Food Science and Technology, University of California, Davis, 1 Shields Ave., Davis, CA 95616; phone: [phone]; fax: [phone]; email: [e-mail].