The films, made from essential oils including oregano, clove and rosemary, were applied to the surface of the meat “as a second skin” that were undetectable by consumers, said researcher Idoya Fernández Pan, of the Public University of Navarre.
The agricultural engineer said her PhD research focussed on chicken meat and studied how the application of a range of essential oils incorporated into a coating helped to enhance shelf life.
“These are highly perishable foodstuffs, given their richness in nutrients and high surface moisture, which give rise to rapid colonisation and growth of a wide range of micro-organisms which are potentially highly altering, even pathogenic,” she said.
The coatings are made up of a series of antimicrobial agents that were incorporated into the structural matrix of the product, and then gradually secreted on to the surface of the meat.
Fernandez said: “Through a bacteriostatic effect, which impedes the proliferation of bacteria, the speed of growth of the pathogen and/or altering agent is reduced, thus enhancing the food safety of the product and extending its shelf life”.
Oregano
The antimicrobial properties of essential oils are well established. The Spanish researcher chose eight different essential oils: oregano, clove, rosemary, white thyme, tea tree, coriander, sage and laurel.
Edible films and coatings containing different concentrations of these oils were developed and these were shown to be effective against various microbial strains such as Staphylococcus aureus, Salmonella enteritidis, Listeria innocua and Pseudomona fragi.
Films and coating containing oregano essential oil were found to have the greatest in vitro antimicrobial efficacy against food pathogens such as S.enteritidis and S. aureus, against altering bacteria such as P. fragi and against real mixed populations from different stages of storage of the chicken breast.
Significantly, the project found that application of the oregano-based coating boosted shelf life by almost half to around 13 days in the case of chicken breast which was stored in a refrigerator.
Fernandez said that “generally speaking, the shelf life of fresh meat products is about 4-9 days depending on the product and the conservation system employed”.
She added the results of her research potentially had a direct application for the food industry, “given its delaying effect on the microflora growth and so extending storage and distribution time for the products”.