Aflatoxin a growing concern

by Nick Reynolds and Stephen Jacobs
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As the food industry in Europe tries to cope with the crisis of beef products contaminated with horse meat, reports of a far more alarming nature have appeared in newspapers throughout the world. They report the disturbing emergence in foods and foodstuffs of the naturally occurring, carcinogenic mycotoxin called aflatoxin B1. In vulnerable humans and animals, aflatoxin is known to cause kidney and liver damage, suppress the immune system and disrupt absorption of nutrients, among other problems.

Aflatoxin is produced by the yellow-green mold Aspergillus flavus. It can be triggered in crops stressed by severe heat and drought, and, critically, can appear both pre- and post-harvest, depending on conditions. Pre-harvest, the presence of aflatoxin is favored by high temperatures, prolonged drought conditions and high insect activity. Post-harvest, warm temperatures and high humidity provide the optimum conditions for aflatoxin during storage. This heat-stable toxin can develop in all cereals such as corn (maize), rice and wheat, and in other dried foods such as pulses and nuts. Further, it can find its way into products based on these raw materials as well as into the milk of animals fed on contaminated feed.

Drought impacts corn

As a result of the prolonged period of drought in many U.S. corn-producing states and the high rainfall and hot temperatures found in Europe during 2012, aflatoxin contamination represents a worrying threat for all grain producers and the manufacturers of corn-based products. Although the U.S. has experienced similar drought conditions in previous years, such prolonged and widespread high temperatures as prevailed in 2012 have already prompted the U.S. Food and Drug Administration (FDA) to grant approval for states in its prominent corn-growing regions such as Iowa, Illinois, Indiana and Nebraska to increase the amount of aflatoxin-afflicted corn that can be blended with “clean” corn for use in animal feed.

However, despite the mitigating steps being taken and all of the most optimistic projections regarding the quality of corn from the 2012 harvest, recalls and product alerts have already begun to spring up in newspaper headlines throughout the world.

At the end of last year, one multinational producer of sweeteners and starches adjusted its sourcing policies after discovering its U.S. corn supplies were contaminated, and in Serbia authorities instigated inspections of the country’s entire 2012 corn crop, following reports that as much as two-thirds of it had been contaminated with aflatoxin. At the beginning of 2013, alerts such as these escalated into specific product recalls, such as the Ohio-based pet food manufacturer forced to recall five different product lines following a random in-store inspection by the Iowa Department of Agriculture.

Milk made the headlines in Europe, where tankers of milk contaminated with aflatoxin were identified and traced back to a number of dairy farms by The Netherlands Food & Consumer Product Safety Authority. And in Germany, authorities were forced to conduct emergency safety tests on milk after it was discovered that thousands of farms in Lower Saxony had received feed contaminated with aflatoxin. Delivery of milk from several hundred farms was suspended, because cows were suspected to have been fed up to 30 times the accepted levels of the toxin.

Given that the World Health Organization (WHO) has recognized aflatoxin in cow’s milk as one of the leading causes of liver cancer in humans, such concern is only natural but has the potential to cause significant public alarm. Already across all European Balkan states, countries have pledged to increase the quality control of their cattle feed and milk in a bid to reduce the levels of aflatoxin appearing in food products derived from “fungus-infected” corn. Purchasers of corn-based feed are urgently seeking alternative ‘clean’ supplies, as concerted action is taken across the board to reduce the risks.

It is not likely that those companies and farmers sourcing the contaminated stock had been aware of the state of their incoming material. According to the Iowan pet food manufacturer, the corn in its pet food had been tested before it was blended and after production of the finished products. This highlights the scale of the challenges involved with tackling aflatoxin. The presence of contaminated corn in the supply chain not only jeopardizes product safety but also threatens commercial relationships and trust, contracts, and the future of businesses up and down the chain.

So far, only a few reports of such incidents have reached the consumer level, but the fact is that much of the 2012 harvest will not reach this far along the supply chain. Instead many tonnes of corn are probably still languishing in grain storage bins with the prospect of being sold at best at minimum price or at worst thrown away, leaving many farmers counting the costs of a worthless crop.

According to reports in the U.S., several grain buyers have already begun posting aflatoxin discount schedules, and prices of “good” corn are inevitably set to rise during the year — the better the quality and the rarer the supply, the higher the price. Exacerbating the problem is the fact that the blending of contaminated samples with “clean” product requires ready access to supplies of clean corn, and the latest aflatoxin threat comes at a time when corn inventories from the 2011 harvest are already depleted.

Finding a solution

Extensive field trials have taken place in northern Italy to establish the best flowsheet for a cleaning line combining both mechanical and optical sorting technologies in order to provide a solution for aflatoxin reduction in maize. Tests over several months with input contamination to the line in the region of 100-200 ppb (parts per billion) have shown consistent reduction to levels below the safe limit for animal feed of 20 ppb and typically producing product with a level of around 11-12 ppb. This vital solution from Bühler could provide corn producers with that potential “miracle” they’ve been waiting for. It allows those sitting on stocks, currently worth next to nothing, to rediscover value in this “lost” product. It helps corn producers recoup rejected material and achieve a viable market price for it, while maintaining their important supply chain relationships and reputation.

With climate change threatening to produce the same attractive conditions that favor aflatoxin development in the coming years, the introduction of such solutions could not be timelier for mitigating contamination risks and optimizing corn supplies in the future.

Bühler has developed a cleaning line for reduction of aflatoxin in maize, which includes classifiers, aspiration, gravity separation and optical sorters. The specific combination of equipment in the line can be tailored to the individual requirements taking into account the condition of the material being processed and the acceptable levels in the final product. Bühler has recently developed a new sorter based on its SORTEX A series of sorters just in time to cope with the problems in Italy where a number of these units have been supplied. They are particularly suitable for this application due to their high capacity and stable operation.