Edible coatings kill food-borne microbes

NEW YORK, Nov 30 (Reuters) Edible coatings containing oils from oregano and other sources can destroy food-borne microbes, enhancing the safety and shelf life of fresh food, according to a team of chemists at the University of Lleida in Spain and at the US Department of Agriculture in Albany, California.

Essential oils of some plants act as food preservatives and are safe to eat, USDA's Dr Tara H McHugh told Reuters. ''We have made films without antimicrobial activity from many different fruits and vegetables, and found that natural essential oils can easily be incorporated, which improves the overall quality of the film.'' For their current study, reported in the Journal of Agricultural and Food Chemistry, the investigators prepared apple-based films.

They then tested the antimicrobial activity of essential oils of oregano, lemongrass, and cinnamon, by measuring their ability to destroy Escherichia coli O157:H7, a microbe that causes food poisoning.

The oil of oregano was the most potent. At a concentration of 0.1 percent, oregano oil was effective after just 3 minutes when added to the film-forming solution. In contrast, 5-fold higher concentrations of lemongrass and cinnamon were required to achieve the same antibacterial activity.

McHugh compared their films to fruit wraps that are sold in supermarkets. ''Our films are much thinner so that they are more flexible, and dryer, so they're not sticky (like fruit wraps).

Our products also have at least 85 percent fruit or vegetable content.'' ''This is a beginning of a three-year research project funded by the USDA,'' she continued. ''We will be screening herbal oils and extracts from products containing polyphenolics, like teas, grapes, and plums, which are known to have antimicrobial activity on their own.'' They will also measure the bactericidal activity of the plant-derived compounds against other bacteria, including Salmonella, Listeria, and Bacillus cereus, and evaluate films in real-world conditions, when they are applied to fresh cut fruit, vegetables and meat.

Reuters HS DB0944