FAYETTEVILLE, ARK. – Ready-to-eat meats are popular with consumers, but after initial processing they are also vulnerable to recontamination by pathogenic bacteria. A solution turns out to be applying an antimicrobial-incorporated edible film coating that will fend off the pathogens.
"We have used film coatings with raw and cooked ready-to-eat meat products," said Navam Hettiarachchy, a food science professor in the University of Arkansas System’s Division of Agriculture who led the research for the Food Safety Consortium, a group of universities that include Arkansas as well as Iowa State University and Kansas State University. "We have also included red meat in our studies as well. In all these products, we have observed a protective effect of antimicrobial incorporated edible films against the pathogens."
The researchers used a whey protein film coating as a vehicle for the antimicrobials. The actual barrier to pathogens was provided by various combinations of grape seed extract, nisin (a peptide, protein fragment), malic acid and EDTA, which is a ring-forming compound of metal ion known as a chelator.
The tests showed effective results in controlling the growth and recontamination of Listeria monocytogenes, Salmonella Typhimurium and E. coli O157:H7 on ready-to-eat meat products. Hettiarachchy’s team tried different combinations of the antimicrobials and found some variances in levels of effectiveness. For example, in experiments on turkey frankfurters, a combination of nisin, malic acid and EDTA was more effective against E. coli O157:H7 when grape seed extract was not part of the mix than when it was included.
"In most of the cases we focused on the type of meat products," Ms. Hettiarachchy said. "The types of proteins, lipids and other components will vary in each meat product. The protective effect is based on the type of antimicrobials and the product matrix, and the film acts as a vehicle to deliver antimicrobials."
She said the film containing antimicrobials was effective for reducing pathogens on raw chicken, ready-to-eat chicken and red meat, and the degree of effectiveness was dependent on the product.
The key to the workings of edible film on meat is the ability to sustain the release of antimicrobials against the pathogens. The antimicrobials are held in the film matrix by weak forces, not by chemical bonding.
"The antimicrobials can be released immediately or the release can be delayed from the film matrix based upon the affinity of antimicrobials to various amino acids and others that are present in the film," Ms. Hettiarachchy said. "A greater affinity of antimicrobials to the film matrix will facilitate sustained release of antimicrobials and will extend the shelf life of the product."
Some industrial interest is already being shown in the edible film. Ms. Hettiarachchy said there are prospects of its commercialization and some companies are looking into its use for coating fruits, vegetables and even flowers.