Smallholder farmers in Sub-Saharan Africa lose up to a third of their grain after harvest, because they often use poor grain storage technologies and ineffective drying practices. Staples like maize stored on-farm are exposed to infestation by insects and fungi. These can lead to contamination with mycotoxins — in particular, aflatoxins, poisonous food toxins produced by Aspergillus fungi. At high doses, aflatoxins can kill, while at chronic exposure, they impact consumers’ health, suppressing immune systems, hindering child growth and even causing liver cancer. Kenya is a particular hotspot for aflatoxins, as regular studies show widespread contamination along the food chain, from maize grain to milk and meat.

Hermetic bags and proper drying keep food toxins at bay

Initial data from USAID-funded Feed the Future Innovation Lab for Food Processing and Post-Harvest Handling (FPL) suggest that affordable hermetic bags and hygrometers could prevent post-harvest crop losses and harmful food toxin contamination. This project is a collaboration between the International Maize and Wheat Improvement Center (CIMMYT), Kenya Agricultural & Livestock Research Organization (KALRO) and Purdue University.

Jacqueline Namusalisi, part of the FPL research team, explains the design of the study conducted May 2017-May 2018 in Kiboko, Kenya. ‘’We first inoculated maize grain samples taken from villages in Nakuru country with fungi responsible for aflatoxin and fumonisin contamination, two major food toxins found in spoiled maize grains. We then compared the performance of various hermetic containers and bags sold on the market, with farmers’ usual storage practices over one year.’’ The ten storage technologies were metal or plastic silos and more affordable hermetic triple layer bags of different brands costing around $2 to $2.5.  

Namusalisi and her team measured maize grain quality parameters such as grain damage, weight loss in storage, fungal growth and mycotoxins, food quality and seed germination. “If these bags are sealed properly, oxygen cannot get in or out. This creates an anaerobic environment that suffocates grain-damaging insects and prevents fungi from growing,” explains CIMMYT economist Hugo De Groote.

‘’Using these bags, farmers may not need (to use) harmful pesticides as they often do,’’ he adds. Purdue Improved Crop Storage (PICS) bags had three time less aflatoxin than farmers’ woven bags impregnated with insecticide after eight months. Moreover, Namusalisi’s study revealed that pesticides such as actellic powder cannot prevent some insect infestation such as the maize weevil after several months of storage.

The Africa Technical Research Center (ATRC) is involved in the development of some of the hermetic bags that were tested during the study. ATRC director, Johnson Odera, noted, “Most of the insect infestations start in the field. When the farmer harvests and transports the maize home, the grain is already infested. The damage can be extensive depending on the level of infestation. One of the ways to minimize the losses, while keeping the food safe for consumption is to use hermetic bags.”

"Moisture is another important factor," adds Namusalisi. Farmers usually store their maize grain in wet conditions and in simple 90kg polypropylene or woven bags that cost less than one dollar ($0.70), and some use pesticide to avoid borer and other insect spoilage. Researchers looked how grain quality evolved if the grain was initially dry (12-13 percent moisture level) or wet (14-15 percent). Results showed that wetter grains degrade quickly (discoloration) and are more prone to mycotoxin contamination.

“Farmers could put maize grain samples in a plastic bag and insert a low-cost hygrometer to read moisture content after temperature is stabilized in 15 minutes. They then know if their grain is safe enough for storage or not. However, standard hygrometers cost around $100, which is out of reach for many small farmers,” says Purdue University professor Jacob Ricker-Gilbert.

Still some questions for large scale adoption

Prices of these post-harvest technologies and lack of awareness are barriers for adoption. Unlike normal storage bags that cost about $0.70 each, a hermetic bag retails for $2-$2.50.

A consultation between maize producers and traders in Kakamega suggests that dropping prices by 20 percent had the potential to increase sales by 88 percent. Another market survey in 2017 revealed that farmers were willing to pay an average price of $1.21 for a hygrometer, while traders said they would buy at $1.16 each. As the project was able to get cheap and reliable hygrometers at less than one dollar, commercialization of these devices is feasible. Indeed, one company, Bell Industries, has started to market the devices on a pilot scale.

Training farmers is crucial. Proper grain drying is important, as the results showed, and FPL hygrometers are affordable. But farmers need to take time to check moisture levels before sealing bags, and they should not leave their bags on bare ground. Additionally, triple layer bags may not be properly sealed if not used as instructed. Jacqueline Namusalisi suggests the technology could be improved by using zip locking.

To ensure large-scale adoption of such technologies, an awareness campaign is necessary to sensitize farmers and consumers about mycotoxin health risks and the benefits of using these affordable and effective ways to prevent contamination. All stakeholders must be involved, including farmers, researchers, input and packaging suppliers, millers and other maize value chain operators like dairies and the consumers. Further research is needed to identify what incentives work, like subsidizing these post-harvest technologies or contract farming for quality maize with a premium price.