Investigating Most Effective Anti-Contamination Efforts for In-Shell Pecans

The Problem

Pecans are usually harvested in the fall after they have fallen from trees, giving way to potential pathogen contamination from soil contact. Since pecans are grown and harvested in open environments, there is also potential for cross-contamination of foodborne pathogens from the fecal matter of wildlife and livestock. E. coli are a group of bacteria that normally live in human and animal intestines, and although most strains are harmless, some can produce toxins like the Shiga toxin, which puts those infected at risk for severe gastrointestinal illness and consequent complications such as kidney failure.

The Work

Researchers, led by Jennifer Acuff, assistant professor of food microbiology and safety in the food science department for the Arkansas Agricultural Experiment Station explored whether pre-cleaning pecans prior to application of sanitizers such as lactic acid or chlorine would increase sanitization effectiveness.

The team inoculated pecans with various STEC strains directly or via soil. For direct inoculation, in-shell pecans were sprayed with a STEC cocktail. For soil inoculation, soil was heat-treated to reduce existing microbial populations, and soil was then sprayed with a STEC cocktail before being used to coat in-shell pecans.

Inoculated pecans were put through the following washing treatments for two, five and 10 minutes: 2 percent lactic acid; 1,000 parts-per-million free chlorine; hot water averaging about 185 degrees Fahrenheit; or ambient water averaging about 64 degrees.

After treatments, the liquid from the wash was filtered and examined.

The Results

The study showed that hot water significantly reduced STEC for pecans, with and without soil, and prevented cross-contamination. Treatments such as chlorine and lactic acid were not as effective at STEC reduction but were effective at reducing cross-contamination from re-use of washing water.

Even when STEC was applied directly to pecans without soil present, the sanitizers still didn’t perform as well as expected. However, it was noted that while the in-shell pecans were visibly clean, there was still organic matter present that may have limited the sanitizer efficacy.

Results of the study were published in the Journal of Food Protection.

The Value

Pecans play a notable role in Arkansas’ economy with the state ranking eighth in the United States for pecan production, according to the 2024 Arkansas Agriculture Profile. In 2022, about 9,700 acres of pecan trees were present in the state. Since pecan products do not fall within the rules of the U.S. Food and Drug Administration’s Food Safety Modernization Act, which regulates preventive measures for human food and produce safety, small growers benefit. However, even one contamination incident could lead to stricter regulations for all growers, which the team’s research aims to prevent alongside ensuring consumer safety.

About the Researchers