Toxins in the food chain

LivelihoodsFood ProcessingFood Security
A farmer sells healthy groundnuts in Malawi. Photo: Clive Mear/Tearfund

Compiled by Claire Hancock

Food safety is often a forgotten aspect of food security. Globally much effort has been placed on increasing the quantity of food rather than the safety of food. But according to the Food and Agriculture Organization (FAO), 25 per cent of the world’s crops are affected by the problem of aflatoxin contamination. This is caused by a group of fungi (aspergillus genus) which, if eaten, can cause liver cancer, slow growth in children under five years old and a weakening of the immune system. The Centre for Disease Control estimates that every day more than 4.5 billion people are in danger of being affected by aflatoxins through eating foods which have the fungus growing on them. These include maize, sorghum, paprika and groundnuts.

Groundnuts in Malawi

Groundnuts (also known as peanuts) are a key crop among smallholder farmers in Malawi, who form about 85 per cent of the population. The nuts are a vital source of cash income and contain important vitamins and minerals that keep rural households healthy. However, groundnuts can suffer from aflatoxin contamination, either before or after harvest, especially when they are exposed to moisture and high temperatures. As well as being a risk to people’s health, aflatoxin contamination means farmers cannot sell their products abroad because they do not meet the standards needed for export. 

Twin, a UK-based organisation, and the National Smallholder Farmers’ Association of Malawi (NASFAM) are training smallholder farmers to improve their groundnut production. They raise awareness of the risks of eating groundnuts affected by aflatoxins and train farmers to prevent the aspergillus fungus from growing and to recognise and remove any affected groundnuts before they go to market. 

Preventing contamination

There are a number of ways to prevent aflatoxin contamination in groundnuts: 

When harvesting:

  • Harvest the groundnuts as soon as they are mature. Groundnuts are mature when the inside of the pod shells have dark markings. Immature groundnuts have a higher moisture content than mature nuts. If they are harvested when they are immature, the higher level of moisture makes them more likely to be affected by aflatoxin contamination. But if the groundnuts are left in the ground for too long the pods may split open, which also increases the risk of fungus contamination.
  • To stop the fungus spreading further, sort the crop so that groundnut pods which are broken, or are already contaminated, are separated from the healthy groundnuts.

When drying:

  • Groundnuts need to be dried steadily in their pods as soon as possible after harvest. They should not touch the soil when being dried. Instead use clean sheets, mats, cement floors or raised structures eg drying racks. If drying in the fields, the groundnuts should be dried in their pods in dry, ventilated stacks (where fresh air can reach them).

When shelling and storing:

  • It is best to store groundnuts in their shells. Never store them if the shells are still damp. The groundnuts should be kept in dry, well-aired conditions away from pests and animals. Groundnuts should not be placed directly on the floor, even if they are in bags.
  • Farmers often soak the nuts to help remove the hard outside shells and reach the groundnut inside. However this process encourages the growth of the fungus. Where possible use a machine to shell the nuts instead of soaking. 

When disposing of infected groundnuts:

You can dispose of affected groundnuts as you would other crop waste but it is very important that you follow this advice: 

  • Do not use affected groundnuts to make food for people to eat (eg flour, paste).
  • Do not feed the affected crop to animals as they will also be harmed by aflatoxins. 
  • Aflatoxins are very hard to destroy. You cannot remove them by boiling, burning or cooking. 


With thanks to Andrew Emmott, Senior Manager (Nuts), Twin and Twin Trading Limited for technical guidance.

For more information: Twin Trading www.twin.org.uk and NASFAM www.nasfam.org 

Farm Radio International  Package 97  on growing groundnuts (www.farmradio.org/radio-resource-packs/package-97-growing-groundnuts) and  Package 98  on post-harvest groundnuts (to be published in 2014)


Discussion questions

  • What can you do if you see signs of the aspergillus fungus on your crops?
  • Do people in your community know about this problem? If not, how could you raise awareness?
  • What other foods in your community spoil and cause disease or sickness?
  • How do you know when your food has spoiled or become dangerous to eat?
  • In your own community, how do people stop food from spoiling? Do these methods need to improve?