Grain testing for mycotoxin contamination: are test kits and analytical services fit for purpose?

Authors
Maurizio Paleologo MSc
Laura Petrucco MSc

Category
Microbiology
A survey to investigate topics including the technologies used, the number of analyses conducted, and the test kits’ certifications.

Rapid testing for grainAflatoxin and deoxynivalenol (DON) contamination of grain depends on several factors, primary among them weather conditions in the pre-harvest period. In Europe, aflatoxin in corn is mostly a problem in southern Europe while DON is more widespread in wheat and other grains across the entire continent. The feed industries were the first to use rapid methods to detect mycotoxins in grains because reduced animal farming productivity due to contaminated feed and the consequent economic losses created a high demand for testing. From 1985 to 2000, test kit manufacturers primarily sold ELISA kits to large grain processing plants and feed industries. With the introduction of regulatory limits for mycotoxins in foodstuffs (Commission Regulation (EC) No 1881/2006), the identification and segregation of all contaminated lots of grains became necessary at the earliest stage, just after harvesting. While feed operators generally have laboratories and the ability to use ELISA kits, this was not the case for grain storage companies and small mills. As a result, there was a sharp increase in demand for easy-to-use rapid methods. In response to this large new market, the in-vitro diagnostic industry introduced so-called “strip-tests” (lateral flow devices, or LFDs). In a few years the strips became the standard testing system because they were quantitative, rapid, simple, and not too expensive. Thanks to the availability of rapid on-site testing, each harvest lot can be analyzed, appropriate cleaning and detoxification procedures can take place, and different stocks with different contamination levels can be stored and shipped to different customers. Less-contaminated grains can be used by food industries and some lots with higher concentrations can be sold to feed industries. However, the limit of 20 ppb for aflatoxin B1 in feed and 1250 ppb of DON for unprocessed cereals (1750 in case of corn oats and durum wheat) means that portions of the harvest never makes it to market some seasons. Thanks to high throughput machines that can sort out suspect kernels from the others, large plants can reduce the number of noncompliant lots. In the event that corn contamination remains higher than 20 ppb of aflatoxin, however, the only option is to sell the contaminated lot to biogas plants. Testing, testing, and more testing onsite is necessary.The last obstacle to widespread use of LFDs in grain storage and processing plants was the methanol in the aflatoxin extraction procedure. However, over the last 5 years almost all LFD manufacturer have shifted from methanol-water to organic solvent-free extraction solutions. It is not likely that all extraction chemicals provided by kit manufacturers allow the same recoveries as the classical method but it is now possible for every user to conduct these tests without health risks or the problem of disposing of toxic solvents.
Testing reliabilityGovernmental approval is not required for producing and selling mycotoxin test kits in Europe, nor are Food Business Operators (FBOs) inspected to check whether testing is sufficiently accurate. ISO 17025 accreditation is mandatory for service laboratories but not for FBOs. So how is testing reliability controlled? The end user rarely has the time or knowledge for in-house validation or for maintaining a

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