Vegetable-based Film Could Protect Fresh Fruits and Vegetables from E. Coli Bacteria

In an effort to protect fresh produce from E. coli and other harmful bacteria, scientists are working to develop an edible, all-natural, antimicrobial vegetable-based film that creates an additional layer of protection when applied to fresh fruits and vegetables.

Epidemiological studies suggest E. coli O157:H7 sickens approximately 100,000 people each year with more than 100 fatalities, leaving the food processing industry in a continuous struggle to control the spread of pathogenic bacteria. In recent months, news stories linking E. coli to fresh produce have caused national concern.

Funded by USDA’s Cooperative State Research, Education and Extension Service, Dr. Tara H. McHugh, a food technologist, along with fellow researchers at the USDA’s Agricultural Research Service (ARS) in Albany, Calif., is researching the effectiveness of using plant essential oils in developing the vegetable-based film. Plants already produce and secrete essential oils to protect against attacks from insects and microbes; the layer of film adds an additional layer of protection.

Essential oils from three plants, oregano, lemongrass and cinnamon, were applied to an apple-based film. The antimicrobial efficacy of each film was tested by determining its ability to destroy E. coli O157:H7. Oil of oregano proved to be the most potent antimicrobial agent. At a concentration of only 0.1 percent, the oregano oil was capable of killing more than 50 percent of the E. coli sample in the first three minutes. In contrast, higher concentrations of lemongrass and cinnamon essential oils were necessary to achieve the same antibacterial activity. The vegetable-based films also acted as an oxygen barrier providing additional preservative benefits to fresh-cut produce.

Unlike fruit wraps that are sold in supermarkets, vegetable-based films are thin, dry and flexible. In addition, these products are all natural, containing at least 85 percent fruit or vegetable content. This study is the beginning of a 3-year project that will screen herbal oils and extracts from tea, grape and plums to further evaluate their antimicrobial potential. Scientists will also explore the antimicrobial activity of these vegetable-based films against additional pathogens, such as Salmonella, Listeria and Bacillus cereus. Research results obtained from the fresh produce studies will then be applied to protecting meat products.

The research findings were presented in the November 29, 2006, issue of American Chemical Society’s Journal of Agricultural and Food Chemistry.

The USDA’s Cooperative State Research, Education and Extension Service funded this research project through the National Research Initiative (NRI) Food Safety program. The NRI is the largest peer reviewed, competitive grants program in CSREES. It supports research, education and extension grants that address key problems of national, regional and multi-state importance in sustaining all components of agriculture.

CSREES advances knowledge for agriculture, the environment, human health and well-being, and communities by supporting research, education and extension programs in the Land-Grant University System and other partner organizations. For more information, visit http://www.csrees.usda.gov.