Natural antimicrobial agents find edible film applications.

The use of natural antimicrobial agents can be an effective alternative for controlling the growth of microorganisms. Natural antimicrobial agents--bioactive compounds derived from biological sources--may be generally regarded as safe (GRAS status). Or they may require FDA approval. Edible films that incorporate natural antimicrobials can protect food as well as inhibit the growth of pathogenic and spoilage bacteria. For this reason, incorporating natural antimicrobial agents into biodegradable films might be an ideal solution to environmental and food safety concerns.

The objective of researchers at Tuskegee University was to determine the efficacy against E. coli of lactoferrin and lysozyme that had been incorporated into casein or zein films. The result of their efforts implies that lactoferrin and lysozyme could be used in the edible films to enhance food safety.

Researchers prepared casein films using casein and glycerol as the major ingredients. Zein films were prepared using zein and glycerol as the primary ingredients. The films were cast on a Teflon-coated petri dish with a 15-mm diameter. Scientists tested the mechanical properties and moisture permeability of the films. Three concentrations of lactoferrin (7 mg, 14 mg and 28 mg) and lysozyme (6 mg, 12 mg and 24 mg)--with and without EDTA (4 mg)--were applied to the surface of the films. Then the scientists cut circular discs from the films. The discs were placed on the E. coli.

Investigators used the area of the clear zones on the discs to determine the inhibitory effects of the antimicrobials. The casein films exhibited good mechanical properties, with a tensile strength of 3.4 MPa and an elongation ratio of 215.6%. Films with lactoferrin or lysozyme significantly inhibited the growth of E. coli, exhibiting clear zones on the discs. The inhibitory effects depended on the amount of antimicrobials used.

Further information. Heshmat Aglan, Mechanical Engineering Department, Tuskegee University, Tuskegee, AL 36088; phone: [phone]; fax: [phone]; email: [e-mail].