The Problem

Ochratoxin A (OTA)

Emergence of OTA contamination in coffee

The presence of OTA in green coffee was first reported in 1974 by Levi et al., whereas its presence in the coffee beverage was reported by Tsubouchi in 1988 and Studer-Rohr in 1995. Roasting reportedly destroys between thirty to over ninety percent of OTA present in green coffee - and the residual OTA in roasted coffee is readily extractable in aqueous solution. This means that poor hygiene controls in the production of green coffee leading to OTA contamination can have a negative public health impact on the ultimate consumer.

Since 1980, several studies have reported OTA data for raw coffee. By 1997, data on 625 coffee samples were available, including results of OTA analyses carried out at the Finnish Customs Laboratory for 1996. The distribution of samples origin among the major coffee producing countries shows that in relation to mean export volumes of raw coffee, some producing countries were under-represented, whereas others were over-represented. However, grouped into five geographical regions of producing countries, distributions of export volumes and numbers of samples match quite reasonably.

The overall mean OTA content for the 625 samples of raw coffee was 1.6 ppb. Over 85% of the samples were in the lowest category (undetectable up to 2 ppb). The 1-2% most contaminated samples had a large effect on the overall mean value.

Surveillance of green coffee imported into the UK, Finland and Hungary shows that OTA can occur in coffee from most origins and of all major types, be they washed or unwashed arabicas and robustas. However, there does appear to be a greater occurrence of OTA in unwashed or dry-processed coffees.

The increasing interest of European regulators in the problem of OTA contamination in coffee prompted reactions from the various stakeholders in the coffee business, and resulted in the development of a pilot study, and a subsequent global project, to address this issue.