The impact of caramel and roasted wheat malts on aroma compounds in top-fermented wheat beer

Top-fermented wheat beers are known for their unique aroma. However, the impact of speciality wheat malts on the aroma of these beers and the transfer of odour active compounds from malt to the beer has not been investigated in detail. Three beers were brewed with different malt composition. The grist for each beer contained 50% kilned barley malt and 50% different wheat malts - beer (1) kilned wheat malt, beer (2) kilned wheat malt and caramel wheat malt, and beer (3) kilned wheat malt and roasted wheat malt. The odour active compounds in the beers were identified by aroma extract dilution analysis and their individual impact on aroma was evaluated by quantitation and calculation of odour activity values (OAVs). The results were verified sensorially by comparing aroma reconstitution models with the original beers. Characteristic odour active compounds in the beer brewed with caramel wheat malt were earthy compounds 2-ethyl-3,5-dimethylpyrazine, 2-ethyl-3,6-dimethylpyrazine, 2,3-diethyl-5-methylpyrazine, caramel-like compounds 4-hydroxy-2,5-dimethylfuran-3(2H)-one and maltol, and sotolon with a soup seasoning-like aroma. The aroma of the roasted wheat malt beer was characterised by smoky and phenolic compounds 2-methoxyphenol and 4-methylphenol. Important beer odorants were quantified in the malts to assess their transfer from malt to beer. The results suggest that direct transfer of the odour active compounds in beers was not significant and that they were formed and/or released during the brewing process, confirming earlier results with different barley malts and bottom-fermented beers.