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Ochratoxin A (OTA) in cereals: development of a rapid test; species and conditions favouring development

HGCA PROJECT REPORT No 332

Ochratoxin A (OTA) in cereals: development of a rapid test; species and conditions favouring development

by
J BANKS1, S HOLMES2 and K SCUDAMORE3

1Central Science Laboratory, Sand Hutton, York YO42 2TH
2ADGEN Ltd. Cunningham Building , Auchincruive, Ayr KA6 5HW
3KAS Mycotoxins, 6 Fern Drive, Taplow, Maidenhead, Berkshire SL6 0JS

FEBRUARY 2004

Abstract

The occurrence of ochratoxin A (OTA), which is produced mainly from the fungi Penicillium verrucosum and Aspergillus ochraceus, in cereals is of particular concern to the EU. In response to this concern, recently maximum permissible levels of 5 ppb in raw cereals and 3 ppb in processed products have been set by the EU for OTA.

As a result of the legislation, there was the need for work to be done to identify the causative organism(s) for the production of OTA in cereals and also on the identification of critical control points so that the limits can be met. In addition, it was necessary to develop rapid monitoring methods for OTA in cereals.

This work was part of an EU project on 'The prevention of ochratoxin A in cereals' (OTAPREV) for which the HGCA provided balancing financial support. The areas of the HGCA supported work included:

1. To determine which are the OTA producing fungi and what are the sources of infection
2. To determine differences between cereal species, farming methods and climates on OTA production
3. Development of rapid immunoassay systems for OTA producing fungi and OTA

The only fungus that was found to produce OTA in Europe was P. verrucosum and it was surprising that A. ochraceus was not found in warmer parts. Even with global warming it is not expected that a change in organism is likely, at least in the short term that could affect the storage of grain in the UK . It is concluded that P. verrucosum appears not to be present in the field. The low levels sometimes found at harvest could be where the grain has been inoculated from other sources e.g. from spores and other fungal material left over in machinery from the previous harvest. This would emphasise the importance of machinery and store hygiene.

All evidence points to the prompt and effective drying of cereals at harvest being the major Critical Control Point for preventing the formation of ochratoxin A. Therefore, rapid and effective drying of grain after harvest remains the number one priority for farmers and store keepers.

Prototype laboratory and on-site systems have been developed to detect Aspergillus sp and Penicillum sp. in culture and grain and also determine if they are toxigenic strains. The methods show sensitivity at least down to 104 CFU/g and are thus able to detect the numbers of organisms that could pose a potential problem in grain. Prototype rapid assay kits for OTA (for laboratory or on-site use) have a range of detection from 0.5 to 25 ppb and can be carried out, including extraction, in about 20 minutes. These assays are important additions to the techniques currently available. They provide the tools and therefore the opportunity, for the rapid and inexpensive monitoring of grain for spoilage organisms and the detection of OTA in line with EU legislation at 5 ppb for raw and 3 ppb for processed cereals.

HGCA Project Number: 2320

Price: £8.50

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