Formation of 3‐Deoxy‐4‐Ethoxyhexosones in Model Systems and Beer

ABSTRACT Glycation‐ and caramelization‐derived 1,2‐dicarbonyl compounds are constituents of beer. The compound 3‐deoxygalactosone (3‐DGal) is generated in beer during 3‐deoxyhexosone interconversion by dehydration and rehydration from 3‐deoxyglucosone (3‐DG). The influence of other nucleophiles on 3‐deoxyhexosone interconversion has not yet been assessed. In the present study, the role of ethanol as an alternative nucleophile was regarded, which hypothetically should lead to ethyl ethers of 3‐DG and 3‐DGal. Model experiments showed that a new 1,2‐dicarbonyl compound is formed from 3‐DG and 3‐DGal when the compounds are heated in the presence of ethanol. The quinoxalines of the 3‐deoxy‐4‐ethoxyhexosones (3‐D‐4‐EH) were isolated as a mixture by semi‐preparative HPLC and utilized as a standard during quantitation by HPLC‐MS/MS in the multiple reaction monitoring mode. 3‐D‐4‐EH was quantified in 47 beer samples in concentrations up to 1.5 mg/L, with the highest concentrations in bock and dark beers. Alcohol‐free beers contained only 0.05–0.13 mg/L of the compound. Up to 4% of 3‐DG and 3‐DGal was converted to 3‐D‐4‐EH in beer. The concentrations of the compound increased by 20–70% during a 6‐months storage at room temperature, while the concentrations of 3‐DG and 3‐DGal tended to decrease. The observed reaction represents a new form of nonenzymatic O ‐glycation in food.