Dry chain: Innovation for food safety

A low-cost, low-tech innovation measuring food dryness is preventing the development of mould in stored crops in Tanzania, and improving the quality and nutritional value of smallholder produce. In Cameroon, moisture-testing machines are enabling cocoa farmers to demand higher prices for their beans at the market.

The DryCard can be used to test the moisture content in produce such as rice, maize and dried vegetables. © Horticulture Innovation Lab/UC Davis

A new, easy-to-use device that determines whether dried food is at a low enough moisture content to prevent mould growth during storage, has been developed by researchers at UC Davis University. The so-called ‘DryCard’ is being used by farmers across Africa to prevent aflatoxin contamination and reduce post-harvest losses. When mould grows, it reduces the market value of dried foods, resulting in reduced incomes for farmers. However, this inexpensive indicator is able to inform farmers of the relative humidity of the air around the product and, thus, whether the food is sufficiently dry to prevent mould development.

The DryCard is made from a cobalt chloride humidity indicator strip, printed paper, and a lamination. When placed in a moisture tight container with dried foods, it changes colour within 20-30 minutes, relative to the humidity. Matching the colour of the indicator strip with the scale on the card informs farmers whether the food is dry enough; if the strip turns pink, the food is too wet for storage, but if it turns blue or grey, the food is dry enough. Where food is indicated as ‘too wet’, they should be dried further or eaten before mould can develop. Providing the DryCard is stored without any contact with water, this cheap and effective device can be used multiple times to test the moisture content in produce such as rice, maize and dried vegetables.

In March 2017, the DryCard beat more than 200 entries at an ‘All Africa Postharvest Technologies and Innovation Challenge’ to take first prize. “My hope is that we will find entrepreneurs and donors to help us spread this technology, so that every farmer who dries produce has access to it,” says Elizabeth Mitcham, director of the UC Davis University Horticulture Innovation Lab.

The Horticulture Innovation Lab has distributed 950 cards in 2017 to rice and maize growers in the six regions of Tanzania, at a price of €0.80 per card. Orders have also been placed by the Ministry of Agriculture in Kenya and by a USAID project in Sierra Leone for 100,000 cards.

Meanwhile, in Cameroon, over 8,000 cocoa farmers belonging to the Konye Cooperative (KONACOOP) are getting better prices for their produce after being supplied with moisture-content testing machines by the Cameroon office of the International Institute of Tropical Agriculture (IITA), in August 2014. Prior to this, members were often exploited by buying agents, who took advantage of the lack of testing machines to offer farmers low prices for their produce. However, the machines enable farmers to measure the exact moisture content of their cocoa beans and argue for a better market price depending on the moisture level, which KONACOOP farmers say has greatly improved their incomes. Officials at IITA say that, in future, such assistance will be extended to other cocoa farmers facing similar difficulties. KONACOOP farmers now sell their partially dried cocoa at between €1.2-1.5/kg when the same amount was previously sold at less than €0.90.

James Karuga & Elias Ntungwe

The Technical Centre for Agricultural and Rural Cooperation (CTA) is a joint international institution of the African, Caribbean and Pacific (ACP) Group of States and the European Union (EU). CTA operates under the framework of the Cotonou Agreement and is funded by the EU.