Comparison of Aroma Profiles of Whiskeys Fermented from Different Grain Ingredients

Different grain sources of whiskey have great potential for aroma expression. In this paper, four whiskeys fermented from different raw materials (barley, wheat, highland barley, and sorghum) were compared. Gas chromatography-mass spectrometry (GC-MS) and sensory evaluation were used to determine the composition of the aromatic compounds. A correlation analysis was further conducted between the aromatic compounds and sensory evaluations. Barley whiskey and wheat whiskey had more pronounced fruity, floral, and grain aromas, attributed to esters and terpenes. Barley whiskey had the most compounds (55), followed by highland barley whiskey (54). Highland barley whiskey had the greatest number of unique aroma compounds (seven). It exhibited a unique cocoa aroma related to concentrations of trans-2-nonenal, γ-nonanolactone, 1-nonanol, isoamyl lactate, 2-butanol, and 6-methyl-5-hepten-2-one. Sorghum whiskey had a specific leather and mushroom aroma attributed to 6-methyl-5-hepten-2-one, ethyl lactate, ethyl caprate, phenethyl octanoate, farnesol, α-terpineol, 3-methyl-1-pentanol, and methyleugenol. Alcohols were the main aroma components of grain whiskeys. Isoamyl alcohol (231.59~281.39 mg/L), phenylethyl alcohol (5.755~9.158 mg/L), citronellol (0.224~4.103 mg/L), β-damascenone (0.021~2.431 mg/L), geraniol (0.286~1.416 mg/L), isoamyl acetate (0.157~0.918 mg/L), phenylacetaldehyde (0.162~0.470 mg/L), linalool (0.024~0.148 mg/L), 1-octen-3-ol (0.016~0.145 mg/L), trans-2-nonenal (0.027~0.105 mg/L), and trans-2-octen-1-ol (0.011~0.054 mg/L) were all important aroma compounds in the whiskeys.