and subtropical origin, such as maize, coffee beans, cocoa and soya beans
is usually due to contamination byAspergillusspecies.
It is now appreciated that ochratoxin A is quite widespread at low
levels in foods and it is necessary to add wine, beer, grape juice and dried
fruits (on which the black-sporedA. carbonariusis implicated) to the list.
The most recent toxicological assessment of ochratoxin indicates that it
is not only an acute nephrotoxin but may also cause cancer of the
kidneys and Member States of the European Union have been engaged
in discussions about setting regulatory limits for this mycotoxin. Draft
proposals were published by the European Commission in 1999 but it
was not until 2002 that the following levels were agreed and set out in
Commission Regulation (EC) No 472/2002. For raw cereal grains the
maximum level is set at 5mgKg^1 whereas for cereal products, and cereal
grains intended for direct human consumption, a more stringent level of
3 mgKg^1 was set. For dried vine fruit, such as currants, raisins and
sultanas, the level was set at 10mgKg^1.
8.4.2.3 Other Aspergillus Toxins. Sterigmatocystin (Figure 8.12), a
precursor in the biosynthesis of aflatoxins, is produced by a relatively
large number of moulds but especially byAspergillus versicolor. It is not
considered to be as acutely toxic, or as carcinogenic, as aflatoxin but it is
likely to be quite widespread in the environment and has been isolated
from a number of human foods such as cheeses of the Edam and Gouda
type which are stored in warehouses for a long period of time. In this
situation the moulds grow only on the surface and sterigmatocystin does
not penetrate beyond the first few millimeters below the surface.
Cyclopiazonic acid (Figure 8.13) gets its name because it was first
isolated from a mould which used to be calledPenicillium cyclopium
(now known asP. aurantiogriseum) but it has subsequently been isolated
from Aspergillus versicolor andA. flavus. In the latter, it is formed
primarily in the sclerotia and there has always been a suspicion that some
of the symptoms ascribed to the ingestion of food contaminated by
A. flavusmay be due to the presence of this compound as well as to the
presence of aflatoxins.
Figure 8.12 Sterigmatocystin
Chapter 8 289