Detecting mycotoxins in situ

Modern analytical techniques can help food producers to quickly and economically detect mycotoxins - harmful metabolic products of mould - at the processing location.

Even small quantities of mycotoxins can be toxic to people and animals. Over 350 mycotoxins, including aflatoxins, ochratoxins, ergot alkaloids, fusarium toxins, patulin and alternaria toxins, originating from over 250 species of mould have now been discovered. Symptoms of poisoning can include liver and kidney damage, weakening of the immune system, damage to the skin and mucus membranes and hormonal disturbances such as fertility disorders. In addition, some mycotoxins are carcinogens and some can lead to genetic defects.

Boiling, baking or frying foods does not help to kill off these heat-resistant substances.

In Australia the most important fungi causing toxic effects in humans and animals are the species that produce aflatoxins. These fungi (Aspergillus spp.) have a particular affinity for nuts and oilseeds, particularly peanuts, corn and cottonseed. In general, control of aflatoxins relies on screening techniques, such as examination under UV light for corn, cottonseed and figs or by electronic colour sorting of peanuts.

Aflatoxins were the first mycotoxins covered by legislation and Australian regulations permit 15 µg/kg total aflatoxins in peanuts and treenuts but no statutory limits have been specified for other foods.

Good manufacturing practice and HACCP guidelines demand tracking down mycotoxin contamination and processors should be able to prove through tests that their products do not contain any of the poisonous substances.

Taking control with the test strip

Analytic methods sensitive enough to detect mycotoxins have been around since the 1970s. The challenge today lies in developing appropriate procedures for on-site controls, in order to quickly and simultaneously detect mycotoxins in food products. Although laboratory testing is very exact, it is also costly and time-consuming, and rapid-response methods provide results in a shorter time. Immunological procedures such as ELISA (enzyme-linked immunosorbant assay) and lateral flow tests, as well as chemical tests such as fluorimetric testing, offer more cost-effective methods of identifying aflatoxins and are helpful in routine daily work. With these tests even untrained staff can identify contaminated specimens without the need for laboratory conditions.

The lateral flow test, for example, can detect individual mycotoxins in just five minutes. In principle, the test system works like a rapid response test strip: if aflatoxin is in the sample, a test band will become visible; if not, it will remain unchanged. This provides a reliable test against the toxins, not only in corn and grain, but also in nuts, figs and, to a certain extent, spices. Another advantage is that the test can be used without any technical equipment, even directly on delivery of raw produce.

The ELISA method is just as fast and cost effective: this can detect fusarium toxins in barley, oats, rye and corn. The microtiter plate test finds the substances on the basis of antigen antibody reactions in less than 20 minutes and allows for a high sample flow rate.

The analytic techniques of tomorrow can stop mycotoxins in their tracks

Rapid tests serve only to provide an estimation of the toxic content in food products. More precise results require detection through high-performance liquid chromatography or mass spectrometry. New techniques should provide solutions: scientists want to trace the substances using infrared laser spectroscopy.

The European Commission’s mycospec project is based on new laser diodes with an emission wavelength in the middle infrared range. “They can be tuned across a wide spectral range, meaning the mycotoxins’ complex signatures can be captured in infrared,” explains Prof. Dr Boris Mizaikoff, head of the Institute for Analytical and Bioanalytical Chemistry at the University of Ulm.

Using this measuring technique the samples can be prepared quickly on-site, which simplifies monitoring limit values. The project group hopes to have the prototypes ready by 2015. Just as practical is the project facilitated by the food industry’s research group to develop a biosensor array, which should be able to detect all relevant mycotoxins in grain and grain products. It is anticipated that the biochip detects up to five mycotoxins in under 11 minutes.

Those interested in  mycotoxin detection will be able to find out more at Anuga FoodTec - the international supplier trade fair for the food and drinks industry. This exhibition will present an up-to-date and comprehensive overview of new technologies, facilities and supplier components for all areas of food and beverage production from 24 to 27 March 2015 in Cologne.