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Should we be worried about Ochratoxin A in coffee?

If this article were appearing on the Mail Online, this article would probably be accompanied by the headline ‘Killer Brew – Will Your Morning Cuppa Give You Cancer?’ or some such hysterical nonsense. Thankfully, we here at DR Wakefield are much more level-headed than the Fleet Street contingent, trading on useful information rather than shock value.

However, there is no doubt that Ochratoxin A (OTA) should be a concern for everyone on the coffee food chain, from growers to roasters to consumers.

Let’s start with the basics, what exactly is it? The toxin OTA is produced by a mould that is found on green coffee beans. OTA is one of several naturally occurring toxins, known as mycotoxins, which are produced by moulds that grow on crops in the field or in storage. OTA also appears in cereals, bread, beer, wine and dried vine fruits.

This mould is the species of two genera of fungi – Aspergillus and Penicillium – that grow naturally on cereals, grapes, coffee and cocoa. In coffee, the most important OTA-producers are Aspergillus ochraceus, A. carbonarius and strains of A. niger.

The main cause of OTA growth is poor coffee harvest and post-harvest practices. In particular, poor drying, re-wetting and bad storage practices in the post-production handling of coffee commonly lead to mould growth which can result in the formation of ochratoxin A.

The Food and Agricultural Organisation of the United Nations (FAO) has set a maximum tolerable OTA limit for humans of 100 billionths of a gram per kilogram of body weight per week. The EU sets maximum permissible limits for OTA of five parts per billion (ppb) in roasted and ground coffee, and 10 ppb in instant coffee. However, as yet, there is no defined limit for green coffee.

If these limitations are not adhered to, there can be serious consequences for the people that drink the affected coffee. Too much OTA can be toxic and the possible side effects for humans include severe kidney damage and potentially a carcinogenic effect.

With the possibility of such serious repercussions, what implications does this have for coffee businesses?

70 billion a year industry

Each day a staggering 2.5 billion cups of coffee are consumed across the globe. With millions of people's livelihoods depending on the industry both directly and indirectly, the importance of safe and healthy coffee production and sale cannot be overstated.

Globally, coffee sales each year exceed $70 billion. If OTA levels are not controlled and coffee production is held up due to OTA contamination, the economic repercussions for many coffee-producing countries and businesses that rely on the bean to make a living would be devastating.

Five year investigation

The FAO, in close collaboration with the International Coffee Organization (ICO) and with funding from the Common Fund for Commodities (CFC), launched a five-year project in 2001 with the main aim of assisting countries to develop national capacities for minimising OTA contamination of green coffee.

This plan was implemented in national institutes in Brazil, Colombia, Côte d'Ivoire, Ecuador, France, India, Indonesia, Kenya and Uganda, and resulted in the production of the Guidelines for the Prevention of Mould Formation in Coffee.

The project concluded that, post-harvest, the most effective way of preventing mould formation and OTA contamination in coffee is to ensure a safe moisture content. This level has to be achieved as quickly as possible and the prevention of re-wetting the beans is key.

Tests confirmed that the ICO's existing recommendation for maximum moisture content in green coffee (12.5%) is consistent with the prevention of growth of OTA producers.

There is still a lot of work to be done in terms of understanding the contrivances involved in mould contamination and OTA build-up, however, as the project found that OTA contamination of coffee beans while still on the tree can be significant.

Should we be worried about OTA?

OTA levels drop during the roasting process: different coffees are generally blended together, meaning that the occurrence of OTA is generally not consistent in a batch. The other concern is the reliability and consistency of the testing process.

If roasters buy good quality, washed coffee, they are unlikely to be affected. Naturals and lower grades do have the potential to carry some OTA, but these coffees are highly likely to be blended anyway – so if, for example, a roaster purchased a robusta natural which had 20ppb, and used it in 10% of their blend, the roasted product would likely only have about 2pbb – well within the limits.

Maintaining high quality control procedures and sourcing from quality control-aware suppliers should be sufficient.

It is clear that controlling foodstuffs which feature inherent toxins is very important, but the levels that occur are generally so small and irregular that we should not get carried away with the worry. Correctly processed and handled coffee has an extremely low level of contamination.

Keeping it safe

Here at DR Wakefield, we work with professional suppliers who ensure that their coffee is prepared in the correct manner. We make sure it is packed in suitable bags/sacks and shipping containers, and that it is stored in a coffee-only warehouse.

All shipments are evaluated for defects and cupped: when smelt and inspected, we will generally pick up any mould issues. However, some coffee, usually that which is naturally processed and lower grade, will sometimes have a degree of mould present, which is why storage and keeping it dry is key to ensuring low levels of OTA.

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