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There are mainly two options for the dealcoholization of beer: evaporation of ethanol by heat treatment, whereby desired aroma-active compounds are also removed, and stopped fermentation that leads to beers still containing high amounts of unfermented sugar in parallel with lower amounts of aroma-active fermentation products. Thus, dry-hopping could be an opportunity to compensate for these aroma deficiencies. Therefore, following the sensomics approach, odorants were characterized in dry-hopped (Hallertauer Mandarina Bavaria, Hallertauer Cascade, or Hallertauer Mittelfrüh) top- and bottom-fermented alcohol-free beers either after thermal dealcoholization or stopped fermentation. Twenty-three odorants were quantitated via stable isotope dilution analysis, and odor activity values (OAVs; ratio of concentration to odor threshold) were calculated. Thermally dealcoholized samples showed high losses (up to 100%) of key odorants like 3-methyl-1-butanol or 3-methylbutyl acetate. During stopped fermentation, aroma compounds like ethyl butanoate or 2-phenylethanol were formed in relevant concentrations, leading to OAVs ≥ 1, but the amounts were significantly lower compared to beers with normal alcohol contents. For hop-derived odorants (linalool, geraniol, myrcene, and esters), transfer rates between 20 and 90% were found, leading to OAVs ≥ 1 in beer. Furthermore, hop addition apparently induced the formation of ethyl esters of hop-derived monocarboxylic acids.

The use of hops in beer brewing is mainly based on its content of bitter acids and aroma compounds. Due to the loss of volatile odorants during wort boiling, the so-called dry hopping is a possibility to intensify the hoppy aroma in the final beer. To clarify the potential of different hop varieties for aroma modulation of beer via dry hopping, key aroma compounds of three different hop varieties were characterized using the sensomics approach. Aroma extract dilution analysis revealed 41 aroma-active compounds, of which 39 were identified via gas chromatography-olfactometry and gas chromatography-mass spectrometry. The highest flavor dilution factor was determined for myrcene with a geranium-like odor. Fourteen substances were quantitated by stable isotope dilution analysis and further two odorants via the internal standard method; all of them revealed odor activity values (OAVs; ratio of concentration to odor threshold) ≥1. Linalool, 3-methylbutanoic acid, myrcene, and dimethyl trisulfide showed the highest OAVs (>1000) in all analyzed hop varieties. For validation of the analytical data, reconstitution models were prepared by adding all quantitated aroma compounds with OAVs ≥ 1 in their naturally occurring concentrations to cellulose as matrix. All three recombinates showed a very high similarity to the aroma profile of the respective hop sample, confirming the correct identification and quantitation of all key aroma compounds.