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Essential oils show promise in fight against foodborne illness

In the quest to eradicate foodborne illness in fresh produce, a scientist at Washington State University is experimenting with alternatives to the traditional chlorine-based postharvest wash, and her results have promising implications for both food and worker safety.

WSU associate professor and Produce Safety Extension Specialist Faith Critzer and a team of scientists from the University of Tennessee and the University of Georgia recently published a study investigating the efficacy of essential oil emulsions in mitigating Salmonella cross-contamination in fresh produce. Essential oils, long known for their antimicrobial capabilities, have been studied extensively for use in food processing. But because oil and water don’t naturally mix, their potential for application in postharvest produce washing systems has never been thoroughly examined.

Until now.

bottles of oil emulsions
Emulsions of thyme and clove bud oil tested by Critzer and her team.

Critzer’s work, published in the Journal of Food Protection, found that both clove bud oil and thyme oil perform as well or better than chlorine in clean washing systems and are more effective than chlorine in wash tanks where organic matter is present.

Every year, outbreaks of foodborne illness are traced back to contaminated produce. In 2008, a Salmonella outbreak in the U.S. sickened 1,500 people and was linked to contaminated jalapeño and serrano peppers. Pathogen contamination can occur in a variety of ways—from contaminated irrigation water, insects, wild animals, even farm employees.

Postharvest washing helps ensure that fresh produce is pathogen free.

While precautions are taken to ensure produce safety at every step in the growing and packing process, postharvest washing is one of the most crucial steps in ensuring that pathogens from the farm don’t make it to the market. To help eliminate pathogens, water used in the postharvest wash typically incudes a sanitizer, such as chlorine, and, while effective in reducing the risk of microbial contamination, chlorine creates potentially carcinogenic byproducts in certain situations.

“Alternatives to chlorine treatment are of interest to both conventional operations as well as USDA certified organic farmers,” said Dr. Critzer. “Every grower cares about the safety of their product and the safety of their workers. We’re looking for alternative sanitizers that ensure produce safety but also mitigate the risk posed by exposure to carcinogenic disinfection by-products. Our study of clove bud and thyme oil emulsions demonstrates that essential oils have real potential for postharvest application.”

While their study’s results are an important step toward finding alternatives to chlorine treatment, Critzer and her team recommend that further research be conducted to determine economic feasibility, postharvest quality and sensory effects of emulsified essential oil wash treatments.

Media Contacts

Faith Critzer, Associate Professor & Produce Safety Extension Specialist,