Date: September 2016
Mycotoxins are low-molecular metabolic products from the secondary metabolic processes of mould. Over 400 toxic metabolites are known, of which about 20 appear in critical concentrations in foodstuffs and animal feeds. Important examples of these are: Aflatoxins, fumonisins, deoxynivalenol, ochratoxin A, patulin, zearalenone, alternariatoxins, citrinin and T2/HT2 toxins. Contamination by toxins can either be primary (field toxins) or secondary (storage toxins). A primary contamination occurs if the plant-based raw material was already infested with toxin-forming mould in the field. The resulting toxins include, for example, deoxynivalenol, zearalenone, fumonisins or T2/HT2 toxins. A secondary contamination occurs if foodstuffs and animal feed become mouldy during storage, transport or processing (aflatoxins on hazelnuts). A rarely occurring contamination of foodstuffs occurs with aflatoxin M1, and is designated a carryover effect. In this case, livestock takes in mouldy feed containing aflatoxins, which metabolises to aflatoxin M1 in the liver and which can then then be excreted in milk etc.
Due to their low molecular weight, mycotoxins do not lead to the formation of antibodies, and depending on type and dosage have acutely or chronically toxic effects. The toxicological risk resulting from the contaminated foodstuff exists above all in chronic intake, in which not just effect cumulative but also substance cumulative effects are observed. Long-term effects include carcinogenic, mutagenic and teratogenic effects. Many mycotoxins have not yet been subjected to sufficient scientific study and accordingly classified, whereas others are classed as dangerous to humans and animals on the basis of their high toxitity levels and frequent occurrence (for example aflatoxin B1).
Fundamentally, mycotoxin content should be kept as low as achievable considing the manufacturing and processing procedures (ALARA principle). The ordinance governing mycotoxins is the EU-wide Directive (EC) 1881/2006, which sets out maximum content of aflatoxins (aflatoxin B1 and a total value for aflatoxins B1, B2, G1 and G2), aflaxoxin M1, patulin, ochratoxin A, deoxynivalenol, zearalenone, fumonisins (total value of fumonisin B1 and B2) and citrinin. There are currently no maximum content regulations for T2/HT2 toxins or alternariatoxins. The Scientific Committee on Food (SCF) prescribes a TDI of T2/HT2 toxins of 0.06µg/kg body weight per day.
Due to the inhomogeneous distribution of mycotoxins in foodstuffs and animal feed, sampling plays a crucial role in being able to determine a product’s precise mycotoxin content. Directives (EC) 401/2006 and (EU) 519/2014 contain criteria for sampling various foodstuffs and batch sizes. There are various methods available for quantifying mycotoxins (fig 1 and 2). At the Institut Kirchhoff GmbH, aflatoxins B and G, as well as aflatoxin M1 and ochratoxin A, are purified using immunoaffinity chromatography. They are then measured using high-performance liquid chromatography (HPLC) and post-column bromination (Kobra cell) with fluorescence detection. For other mycotoxins, such as patulin, deoxynivalenol, zearalenone, fumonisins, alternariatoxins or citrinin, we purify using SPE columns, dispersive PSA, ‘dilute and shoot’ or the internationally established QuEChERS method. Multiple toxins can be determined at the same time using a combination of HPLC and tandem mass spectrometry (HPLC-MS/MS). Quantification is by methods used in our internal standards (isotope labelled).