Fusarium toxins in beer production

Trichothecenes

Trichothecenes are the biggest group of chemically related compounds among the mycotoxins. These sesquiterpenes are produced in cultures of several different species belonging to the Fusarium sections Discolor, Gibbosum, Sporotrichiella and Arthrospori- ella. Moreover, production of trichothecene derivatives (macrocyclic trichothecenes) was found in species from genera Trichoderma, Myrothe- cium, Cephalosporium, Stachybotrys, Cladosporium, Trichothecium, Verticimonosporium and Spicellum as well as in the leaves of the Brazilian shrub Baccharis megapotamica (Jarvis et al., 1991). Trichothecenes occur in all kinds of cereals and food product made therefrom, including malt and beer as well as in vegetables and fruits but also in materials such as building materials, textiles or in the air (spores of Stachybotrys chartarum). According to their chemical structure, all trichothecenes can be categorized into four basic types, i.e. 8-keto-trichothecenes

(type A), 8-hydroxy-trichothecenes (type B), di-epoxythrichothecenes (C) and macrocyclic tri- chothecenes (type D) (see McCormick et al., 2011). Compounds belonging to type A and type B are the most common in cereals and cereal products (Rod- riguez-Carrasco et al., 2013). The trichothecenes most commonly detected in wheat and barley grown in different geographic regions are the type B trichothecenes deoxynivalenol (DON) and its acetylated derivatives 3-acetyl DON and 15-acetyl DON, nivalenol (NIV), and fusarenone-X (FX) as well as the type A trichothecenes T2-toxin, HT2- toxin, and diacetoxyscirpenol (DAS) (Barthel et al., 2012; Ibanez-Vea et al., 2012; Rasmussen et al., 2012; Tittlemier et al., 2013).

Several of the trichothecenes have been found to conjugate with sugars to form glycosides, masking their detection during routine analytical procedures (Berthiller et al., 2013). However, the toxins can readily be released from their glycosidic partner by microbial activity in the human or animal gut to display their full toxicity (Dall'Erta et al., 2013). Assessment of the toxicological potential of regulated trichothecenes such as DON in a sample may therefore be underestimated if only concentrations of the parent toxins are measured during routine analysis. Transfer of deoxynivalenol-3-glucoside (DON-3-Glc) from barley through malting and the brewing process was observed with a steady increase of DON-3-Glc resulting in an excess of the glucoside over the free form of the toxin in the final beer (Lancova et al., 2008; Kostelanska et al., 2009). Recently, Zachariasova et al. (2012) observed the presence of DON-3-oligoglucosides of varying chain length in addition to the monoglu- coside and the unmodified DON in malt and beer, showing that trichothecene analysis may become a more complex task in the future.

The fate of DON as the most widely distributed Fusarium mycotoxin has been studied using immunochemical (Niessen and Donhauser, 1993) or HPLC-based analysis (Kostelanska et al., 2011). Studies revealed that a considerable proportion of DON is washed away from a field contaminated sample during steeping (Beattie et al., 1998). However, levels of the toxin increased during the malting process due to de novo synthesis, adding up to the concentrations already present inside barley grains from field contamination. Most of the toxin was transferred to the wort and no reduction was found during wort boiling, fermentation and ripening so that the finished beer had similarly high concentrations as compared to the corresponding malt (Lancova et al., 2008). It was most interesting to see that final concentrations of ‘masked' DON glycosides were higher than the unmasked derivative.

Rocha et al. (2005) reviewed the toxicological effects and underlying cellular mechanisms of the most common trichothecene mycotoxins in mammals and in plants. Acute symptoms of tri- chothecene uptake are diarrhoea (Matsuoka and Kubota, 1987), vomiting (Ishii et al., 1975), impairment of the immune system, reduced performance of the heart muscle, disorder of the nervous system and skin irritations (see Beasly, 1989). Acute toxic aleukia (ATA, Joffe, 1971), the Kashin-Beck disease (Joffe, 1986; Kolsteren, 1992) and the red mould disease (Yoshizawa, 1983) have been described as human conditions that are associated with tri- chothecenes.

Legal limits have been set for the trichothecenes deoxynivalenol and T2-toxin in several countries worldwide, including the EU, Canada, Russia, and the USA (FAO, 2004). Moreover, a few countries have additional regulations for HT-2 toxin and diacetoxyscirpenol in certain food and feed commodities. Although more toxic than DON, NIV concentrations have undergone no legal regulation yet. However, the toxin might need to be given more attention from a legal perspective in the future (European Commission, 2002).

 
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