Testing drying methods, student looks for key to quality peanuts

By Alex C. Merritt
University of Georgia, Peanut & Mycotoxin Innovation Lab

For PMIL master’s student Monica Chimbaza, the key step in producing a safe peanut crop comes after the nuts are out of the ground.

Peanut crops in Chimbaza’s home country of Malawi are vulnerable to contamination from aflatoxin, a byproduct of naturally occurring molds that infect peanuts, corn, and other crops. Aflatoxin exposure has been linked to cancer, wasting, stunting, and immune deficiencies.

Farmers are not always aware of the dangers of aflatoxin, Chimbaza said, or that the way they dry and store their crop could have a huge impact on whether the nuts become contaminated with aflatoxin.

Monica Chimbaza, a master's student at LUANAR (Lilongwe University of Agriculture and Natural Resources), tested different drying methods, looking for the most efficient way to prepare peanuts for storage.


“Drying and storage are important stages for aflatoxin control,” Chimbaza said. “As such, adoption of good drying and storage technologies would help to improve health and trade in developing countries like Malawi, where aflatoxin contamination drastically reduced groundnut exports to 9.3 percent of total production.”

Aflatoxin contamination in maize, peanuts and other crops costs southern African nations millions of dollars a year in lost trade, a fact that frustrates farmers who are locked out of markets abroad.

Still, peanuts are very popular in Malawi.

“Peanuts are greatly consumed in Malawi in the form of raw, roasted, blanched, or boiled peanuts, or peanut flour mixed with traditional dishes, peanut butter and oil,” Chimbaza said. “Personally, I love fresh, in-shell boiled groundnuts.”

Whether peanuts are consumed at home or shipped abroad, farmers want to produce the safest crop they can. Keeping aflatoxin out of their product means taking action even after the crop is harvested.

“There is a need to achieve food safety in peanut production and one of the ways that food safety could be achieved is aflatoxin control,” Chimbaza said.

With support from the Peanut & Mycotoxin Innovation Lab, Chimbaza is receiving a master’s in Food Science and Technology from the Lilongwe University of Agriculture and Natural Resources. She wrote her thesis on the effectiveness of different drying and storage technologies on aflatoxin management in Malawi.

She began by evaluating 12 common drying methods to see which methods worked the fastest, resulted in highest quality peanuts, and prevented aflatoxin contamination the most. Her results show that the mandela cork and A-frame drying methods were the most effective at reducing aflatoxin contamination and maintaining high quality for the peanut crop. Drying peanuts on the bare ground or on window sills resulted in the highest level of aflatoxin contamination and the lowest quality peanuts.

Chimbaza then stored peanuts in hermetically sealed bags, granary bags, and polyethylene bags to examine the effectiveness of different storage technologies in controlling aflatoxin. After six months, she tested the peanuts for aflatoxin and found that hermetically sealed bags were more effective than polyethylene bags in preventing aflatoxin, resulting in about half the aflatoxin concentration after six months’ storage. The aflatoxin concentration in the hermetically sealed bags increased by just 4 percent over that period.

In Malawi, where the average person lives on less than $2.50 a day, investing in proper drying and storage technologies like the mandela cork and hermetically sealed bags can stretch an already tight budget. Chimbaza’s next step in her research would be to analyze the cost-benefit of technology and educate farmers about why those investments are important in the long run.

“There is need to assess feasibility of the technologies in terms of cost,” she said. “There is also a need to sensitize farmers on the effects of aflatoxin contamination to human health and train them on how best they can manage their groundnuts during drying and storage.”

Chimbaza said that the Malawian government’s support of its farmers makes it easier to disseminate the information that farmers need.

“In Malawi, we have agriculture extension workers in all regions.  If such a group is equipped with all necessary information regarding aflatoxin management methods, then it will be easy to convey the message to the farmers,” she said.

After her master’s program, Chimbaza wants to be a part of that educational process, both by acting as a teacher and contributing towards the body of knowledge that helps farmers reduce aflatoxin contamination.

“I plan to add value to groundnut farmers in Malawi, through trainings of extension workers and farmers. I also plan for more research in community-based innovations for aflatoxin control,” she said.

– Published June 29, 2017