Neither of the OTA-producing species of Penicillium, P. verrucosum and P. nordicum, have been isolated from coffee. P. brevicompactum is common in coffee, and is in the same group as the two producing species, but is not a producer. In coffee, three species or groups of species, all in the genus Aspergillus, are of possible significance:
- A. niger complex
(there is no consensus on speciation in the A. niger-like fungi) is by far the most common of these, particularly in Coffea caneophora (robusta), but OTA production is a rare property amongst isolates and producing isolates are usually feeble producers. One study in coffee revealed one producer amongst the seventy isolates tested (Appendix 12, Report of Pilot Coffee Study [.pdf]). Another recent study of OTA-producing mould in coffee found 2 producers out of 39 isolates of the A. niger complex (Suarez-Quinoz, 2004 - [xref]). Accumulating data from mycological work in coffee will provide a clearer picture of the contribution of these moulds to OTA contamination.
- A. carbonarius is generally
rare but there is some evidence that it can be relatively common in certain locations. Most isolates seem to be capable of OTA production in significant amounts though over a restricted range of environmental conditions.
- A. ochraceus
and related fungi are well distributed in coffee production systems and because OTA production is a common property (about 80% of isolates readily produce OTA), it comprises the most important OTA-producing species in coffee.
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OTA contamination of coffee has been shown to be primarily a post-harvest problem. During post-harvest handling of coffee, adequate control of the water available in the coffee to support mould growth and myctoxin contamination is the best way to avoid this problem.
