Multilayered antimicrobial polyethylene films applied to the packaging of ground beef

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Abstract
A natural antimicrobial agent, grapefruit seed extract (GFSE), was incorporated in a 0.5% or 1.0% concentration on the food‐contact surface of multilayered polyethylene (PE) film by a co‐extrusion or solution‐coating process. The fabricated films were tested in their antimicrobial activity against several food spoilage microorganisms, and then applied to the packaging of ground beef. During the storage of the packaged beef at 3°C, changes in microbial counts, pH, TBA value and meat colour were monitored in order to see the effect of the packaging film on meat quality changes. Coating the PE film with GFSE with the aid of a polyamide binder resulted in a more effective level of antimicrobial activity on the agar plate medium than did its incorporation by a co‐extrusion process. The film co‐extruded with a 1.0% GFSE layer showed antimicrobial activity only against Micrococcus flavus ATCC 10240, while the film coated with 1.0% GFSE showed activity against several microorganisms, such as Escherichia coli IFO 3301, Staphylococcus aureus IFO 3060 and Bacillus subtilis IFO 12113. Both types of GFSE‐incorporated multilayer PE films contributed to a reduction of the growth rates of aerobic and coliform bacteria on the ground beef, when compared to plain PE film. The film coated with a higher concentration (1.0%) of GFSE had a more pronounced effect than did the other films in inhibiting spoilage bacterial growth. They could also slow down chemical changes of the packaged beef. The GFSE‐coated film was more effective in preserving beef quality, but the level of GFSE addition did not affect the quality changes of the beef. Copyright © 2001 John Wiley & Sons, Ltd.