In May 2004, Kenya’s Ministry of Health asked the Centre for Disease Control and the World Health Organisation for help with an outbreak of jaundice in the current Makueni and Kitui Counties that had claimed 125 lives.

When food samples from the two areas were analysed, they tested positive for aflatoxin poisoning. The levels of contamination — 8,000 parts per billion — were way above the allowed limit of 10 parts per billion.

It was after the 2004 outbreak that the government begun an aggressive campaign to control aflatoxin, burning everything that was found to be contaminated.

“In 2014 we had to destroy 155,000 ninety-kilo bags of maize. For a country that relies heavily on maize for food security, that is a lot to lose,” said Sicily Kariuki, former principal secretary in the Ministry of Agriculture and now Cabinet Secretary for Youth and Gender.

READ: War against aflatoxins gets $10.7m govt boost

ALSO READ: EAC forms body to control spread of aflatoxins

But destroying affected crops may not be the only way to deal with contamination, thanks to an ancient Latin American method known as nixtamalisation.

“Nixtamalisation is a Mexican way of food preservation that requires three main ingredients; water, food grade lime and maize,” said Dr Natalia Palacios, a nutrition and quality of maize researcher at CIMMYT based in Mexico.

“You boil the maize in hot water and add lime. Let it cool down for 3 to 16 hours. The following day, you can wash the kernels, remove the outer layer — the pericarp — then mill those kernels.” 

The technology was formally introduced in Kenya this month.

“The nixtamalisation programme is part of the bilateral agreements between Kenya and Mexico, where we have agreed to share ideas and expertise on aflatoxin management,” said Erasmo Martinez, the ambassador of Mexico to Kenya.

“If, for instance, you have 2kg of maize, you need between 10 and 15 grammes of lime and five litres of water. There are several ways to remove the pericarp. Communities do it by simply pounding it but once you boil it in the lime it becomes so soft that it is easy to pull it off by hand,” explained Charles Bett, a senior research officer with the Kenya Agricultural and Livestock Research Organisation.

What qualifies as food grade lime, though, is still under research, but the Mexican researchers say calcium hydroxide is a good place to start. Kenyan scientists said local African communities have several recipes they have used for years to create alkaline mediums they use in cooking, which qualify as food grade lime.

In western Kenya, for example, the Luhya community uses ash made from dried banana peels or bean pods to make the alkaline medium by filtering water through it and then using the solution to cook various meats and traditional vegetables. This solution is called musherekha and it is known to tenderise food. Baking soda and wood ash have also been known to work.

Locally made lime equivalent

“In east and central Kenya, the same solution is called munyu,” Pheanius Nyaga, head of plant protection in the State Department of Agriculture explained. “Our communities have this knowledge already but they don’t know it. If you cook maize in munyu or musherekha, you are nixtamalising it.”

There are a few kinds of lime that are used in Kenya, mainly in agriculture to neutralise the acidity in the soil. Kenya has sent these limes to Mexico for analysis to determine the possibility of their use in nixtamalisation. Preliminary results indicate that they can, as long as they are manufactured as food grade.

How long the maize cooks in the lime, though, will depend on how dry the grains are: The drier they are, the longer it will take to nixtamalise them.

There are two ways to mill the nixtamalised grain. It can be dried in the sun first before it is milled into flour, or it can be wet-milled. This means that the grains are not allowed to dry first. This, however, requires a special kind of mill that uses stones to grind the wet grains into thick dough.

That dough is referred to as nixtamal dough and is kneaded into various other foods including tortillas — or chapatis — and biscuits. Maize in its natural state doesn’t have holding properties like wheat, a characteristic that limits its uses. But through nixtamalisation, maize is able to hold together like wheat.

Latin Americans have used this recipe for centuries, not specifically for the control of aflatoxin, but to make it possible to convert the maize into over 600 other dishes.

But the main reason for its introduction in Kenya is to help decontaminate maize.

“When you remove the pericarp, you remove a percentage of the aflatoxins that are present in the outer layer of the kernel, because that is where contamination always starts,” said Dr Palacios.

She explained, though, that decontamination reduces toxic levels by at 60 per cent, but it will only work if the contamination is just on the pericarp.

“It is impossible to get all the aflatoxin out if it has spread to the inner parts of the grain — the endosperm and germ. If that happens, then there is nothing much that nixtamalisation can do.”

This process reduces the toxins in the pericarp by more than 50 per cent, but by 40 per cent and 15 per cent respectively for the endosperm and germ, which may not give confidence to someone with contaminated grain.

“Yes, that is low, but then you see, you’ll be better off than the one who has not nixtamalised,” Mr Ngari said.

Kenya is the first country in Africa to adopt nixtamalisation. The Kenya Agricultural and Livestock Research Organisation is still doing research into nixtamalisation, mostly to establish what varieties of maize are best suited for it.

At the moment, aflatoxin control is done by the application of aflasafe in the field, which has a proven its efficacy of at least 90 per cent.

Kenya is currently importing its aflasafe from Nigeria, but it is working on a manufacturing plant, which will be the first of kind in the region and the second in Africa after the one in Nigeria.

Last year in April, scientists meeting in Dar es Salaam came up with a protocol on aflatoxin sampling procedures to ease effective regional trade for unprocessed maize and groundnuts.

Sampling protocol

The proposed sampling protocol covers the optimum sample size, the conditions and frequency of sampling grain destined for regional markets.

The protocol will minimise the risks of misclassifying commodities, while enhancing the effective removal of contaminated grain from the supply chains in East and Southern Africa, as well as exports to markets like the European Union that enforce stringent health standards on food imports.

The Tanzania Food and Drugs Administration has documented levels of aflatoxins in maize – the country’s number one staple food — that are way above the recommended maximum limits. On its part, Rwanda has not registered any cases, said Philip Nzaire, Rwanda Standards Board director of quality assurance. He credited this to rigorous inspections and testing of foods, and continuous training of grain producers, dealers and millers.

The aflatoxin challenge constitutes a significant threat to food and economic security, and undermines poverty eradication efforts in Africa. It is a major cause of post-harvest losses that further constrain the ease of food reaching markets and households across the African continent.

Studies have shown that the frequency of contamination in maize and groundnuts produced in Africa is as high as 60 per cent, while actual contamination leads to a 64 per cent reduction in food supplies and quality.

High levels of aflatoxins have been found in countries such as Gambia, Ghana, Guinea, Nigeria, Senegal, South Africa and Uganda. The severe outbreaks in Somalia between 1997 and 1998 and in Kenya between 1981 and 2004 are indications of the magnitude of the problem.

Additional reporting by Julius Barigaba, Christopher Kidanka and Esiara Kabona