Edible food wrap kills deadly E. coli bacteria

Researchers have improved upon an edible coating for fresh fruits and vegetables by enabling it to kill deadly E. coli bacteria while also providing a flavor-boost to food. Composed of apple puree and oregano oil, which acts as a natural antibacterial agent, the coating shows promise in laboratory studies of becoming a long-lasting, potent alternative to conventional produce washes, according to a team of scientists from the U.S. Department of Agriculture (USDA) and the University of Lleida in Spain.

The study comes on the heels of the recent deadly E. coli outbreak in spinach and amid growing concern by experts that some produce-cleaning techniques may not be effective in destroying E. coli. The study is scheduled for the Nov. 29 issue of the American Chemical Society's Journal of Agricultural and Food Chemistry.

"All produce-cleaning methods help to some degree, but our new coatings and films may provide a more concentrated, longer-lasting method for killing bacteria," says Research Leader Tara H. McHugh, Ph.D., a food chemist with the USDA's Agricultural Research Service in Albany, Calif. As the films are made of fruit or vegetable puree, they also provide added health benefits such as vitamins, minerals and antioxidants, she says.

Researchers have known about the antimicrobial activity of plant-derived essential oils for some time, but McHugh says that her group is the first to incorporate them into a fruit- or vegetable-based edible food wrap for the purpose of improving food safety. Three years ago, she and her associates developed a similar edible food wrap, but without the antimicrobial properties.

The new antimicrobial coatings have not been tested on fresh produce yet, McHugh notes. The current study only tested the coatings against E. coli O157:H7, a potentially deadly strain of the common bacterium Escherichia coli, but tests on other foodborne pathogens, including Salmonella, are ongoing or planned in the future, she says. If they continue to show promise, the coatings could hit the consumer market in a year or two, estimates McHugh, whose study is funded by the USDA.

In developing the coatings, McHugh and her associates tested oregano, cinnamon and lemongrass oils in solutions of apple puree and dried films for their effectiveness against E. coli. Each compound was tested in a controlled series of dilutions, the scientists say.

While all of the oils tested inhibited the growth of E. coli, oregano oil was the most effective, killing over 50 percent of sample bacteria in 3 minutes at concentrations as small as 0.034 percent, says McHugh, who's now working on improving the kill rate.

The second most effective oil was lemongrass, followed by cinnamon oil. By contrast, the apple-puree film alone did not kill the E. coli bacteria, the scientist says.

However, an advantage of the apple antibacterial film is that it is composed of sticky sugars and lipids, which allow the coating to adhere to fruits and vegetables for longer periods than conventional, water-based produce washes. That same stickiness also gives the suspended antimicrobial agents a more concentrated exposure to bacterial surfaces, increasing the film's germ-killing potential, the researchers say.

The antibacterial coating could be used by produce manufacturers as a spray or dip for fresh fruits and vegetables, they say. The resulting product will taste a bit like oregano, McHugh says, adding that this can be a desirable trait in salads.

Besides apple puree, the antimicrobial films can also be made from broccoli, tomato, carrot, mango, peach, pear and a variety of other produce items. Non-antimicrobial versions of these food wraps are now being made commercially by California-based Origami Foods® in cooperation with the USDA for use in a small but growing number of food applications, including sushi wraps.

Source: American Chemical Society

Related stories:

E. coli outbreak in Oklahoma kills 1, sickens 200
(AP) -- An E. coli outbreak linked to a restaurant in northeastern Oklahoma has sickened more than 200 people and killed at least one person, state health officials said Tuesday.
FDA: Irradiating spinach, lettuce OK to kill germs
(AP) -- Consumers worried about salad safety may soon be able to buy fresh spinach and iceberg lettuce zapped with just enough radiation to kill E. coli and a few other germs.
Rapid test for pathogens developed by K-State researchers
Dangerous disease often spreads faster than it takes to diagnose it in the lab. To remedy that, researchers at Kansas State University have developed a test to bring that time from days down to hours.
'Edible optics' could make food safer
Imagine an edible optical sensor that could be placed in produce bags to detect harmful levels of bacteria and consumed right along with the veggies. Or an implantable device that would monitor glucose in your blood for a year, then dissolve.
Sesame seed extract and konjac gum may help ward off Salmonella and E. coli
A new study in SCI's Journal of the Science of Food and Agriculture shows that konjac gum and sesame seed extract may offer protection against different strains of E. coli and Salmonella bacteria.
Scientists discover how some bacteria may steal iron from their human hosts
Like their human hosts, bacteria need iron to survive and they must obtain that iron from the environment. While humans obtain iron primarily through the food they eat, bacteria have evolved complex and diverse mechanisms to allow them access to iron. A Syracuse University research team led by Robert Doyle, assistant professor of chemistry in The College of Arts and Sciences, discovered that some bacteria are equipped with a gene that enables them to harvest iron from their environment or human host in a unique and energy efficient manner. Doyle's discovery could provide researchers with new ways to target such diseases as tuberculosis. The research will be published in the August issue (volume 190, issue 16) of the prestigious Journal of Bacteriology, published by the American Society for Microbiology.
Make your own microfluidic device with new kit from U-M
A type of device called a "lab-on-a-chip" could bring a new generation of instant home tests for illnesses, food contaminants and toxic gases. But today these portable, efficient tools are often stuck in the lab themselves. Specifically, in the labs of researchers who know how to make them from scratch.
Microbes beneath sea floor genetically distinct
Tiny microbes beneath the sea floor, distinct from life on the Earth's surface, may account for one-tenth of the Earth's living biomass, according to an interdisciplinary team of researchers, but many of these minute creatures are living on a geologic timescale.

News discussion:

General Science news