Student measures how composting breaks down aflatoxin

By Allison Floyd
University of Georgia, Peanut & Mycotoxin Innovation Lab

For millennia, farmers have composted organic matter to return nutrients to depleted soil.

University of Georgia master’s student and Ghana native Esther Yeboah Akoto wants to be able to show farmers whether that natural process also deals with a problem we’ve only known about the past few decades: aflatoxin contamination.

“We know that composting has been around for a very long time. It’s a technique that growers have used for thousands of years,” she said. “More recently, we know about aflatoxin and its effect on health. Could composting provide a way to remove aflatoxin-contaminated produce from the food supply?”

Researchers around the world are working to minimize naturally occurring molds that can grow on peanuts, maize and other crops. Those molds can generate mycotoxins – such as aflatoxin, a dangerous compound that can stunt children, cause cancer and, in high doses, even kill. Obviously, the most effective intervention is to minimize mold growth in the field and in storage, but farmers may never completely get rid of something as ubiquitous as mold.

For farmers and producers, particularly those in food insecure places, finding a use for crop waste and contaminated food is vital; no one wants to waste part of the crop. In the case of peanuts, Akoto found that many farmers in her home country of Ghana would simply put crop waste back into the ground as a soil amendment.

“There is waste from each season of peanut, but what are we going to do with it? … Since, there is a possibility that aflatoxin can be taken up by plants directly from the soil, we want to be sure that the aflatoxin is broken down.

“Compositing is a very simple technology and farmers need fertilizer. Now, let’s see how composting can be used to break down aflatoxin before farmers put compost back into their fields.”

Microbes including bacteria, fungi, and protozoa have been shown to break down aflatoxin, but Akoto wanted to see how quickly and under what circumstances.

“We have found that some microorganisms can breakdown aflatoxin, which is a promising thing,” she said.

After adding three commercially-sold composting starters to contaminated peanut meal, Akoto evaluated the resulting over six weeks to see how quickly aflatoxin broke down.

The aflatoxin level dropped throughout the test, but most quickly in the first two weeks. While it’s beneficial that aflatoxin levels dropped quickly, some aflatoxin persisted even after six weeks of composting.

Akoto performed the tests at UGA’s Griffin campus and replicated the work at home in Ghana. “We wanted to see how it would work in Ghana to make sure that the conditions were realistic and the data didn’t just come from the lab.”

In Ghana, some of the starting samples contained 3,000 ppb of aflatoxin (astoundingly higher than the 20 ppb that is acceptable for consumption in the U.S.), but that level dropped by 1,000 in just a week.

The results held other good news for farmers without much money for inputs: The samples that weren’t treated with composting starter or accelerant broke down alflaxotin as fast as the samples that were treated.

“It’s a plus for farmers that you don’t need to go buy a product. All you need is peanut meal; it has its own micro-flora,” she said. “If you are giving farmers a new reason to use known technology and, at the same time, telling them it won’t cost anything … that’s a bonus.”

Akoto’s father was cocoa farmer and as a child she spent time in the fields near Kumasi.

“I enjoyed harvesting oranges and learning about what happens on the farm,” she said. That developed into a wider interest in food safety from the field to the market or processor to the final consumer.

“At the market in Ghana, I see food safety issues and think, ‘We still have a long way to go,’” Akoto said.

Akoto is scheduled to complete her master’s degree in Food Science from the University of Georgia this fall and hopes to continue toward a PhD.

Published October 20, 2016