Metabolic fate of trichothecenes during beer fermentation by lager yeast

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Title: Metabolic fate of trichothecenes during beer fermentation by lager yeast
Author: Han, Li
Contributor: University of Helsinki, Faculty of Agriculture and Forestry, Department of Food and Environmental Sciences
Publisher: Helsingin yliopisto
Date: 2015
Language: eng
Thesis level: master's thesis
Discipline: Food Science
Food Science
Food Science
Abstract: Trichothecenes, as a dominant group of Fusarium mycotoxins, have received lots of scientific attention due to their wide contamination of human food and animal feed. Besides native trichothecenes, their conjugated forms the so-called masked mycotoxins, have also been somewhat studied in recent years due to their potential harmful impact. Beer, as one cereal-derived beverage, encounters the threat of trichothecene contamination. During beer fermentation, trichothecenes may be biotransformed into metabolites, which could potentially exert toxicological implications on beer consumers. The aim of this study was to investigate the metabolic fate of several major trichothecenes, including T-2 toxin (T-2), HT-2 toxin (HT-2), deoxynivalenol (DON) and its masked form deoxynivalenol-3-glucoside (D3G) during beer fermentation by lager yeast. A four-day fermentation experiment was conducted with four analytes inoculated in 11.5°Plato wort at the initial stage of fermentation individually or as a mixture with various concentrations. A reliable and efficient method was developed for the kinetic study of trichothecenes by liquid chromatography-triple quadrupole-mass spectrometry (LC-TQ-MS). After four-day fermentation, an approximate 10-40% decrease of all analytes was observed. The missing trichothecenes were very likely bound with yeast cell wall or biotransformed to their masked forms metabolic reactions. Further identification of the masked metabolites was fulfilled by analysing concentrated samples with liquid chromatography-quadrupole-time of flight-mass spectrometry (LC-Q-Tof-MS). Several putative masked metabolites were annotated, including D3G and acetyl-DON in DON-dosed samples, acetyl-T-2 and HT-2 in T-2-dosed samples and T-2/3-acetyl-HT-2 in HT-2 samples. The stability of D3G during fermentation was for the first time investigated and was found stable under brewing fermentation conditions.
Subject: Trichothecenes
masked mycotoxins
metabolic fate
beer brewing

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