Abstract
<p>The aroma of hop volatile oil contains a sweat-like odor. We studied the odorous volatile compounds responsible for the sweat-like odor in the volatile oil extracted from Hallertau Perle hop (<em>Humulus</em><em> </em><em>lupulus</em><em> </em>L.) pellets. The combined use of gas chromatography-mass spectrometry/olfactometry (GC-MS/O), aroma extract dilution analysis (AEDA) by GC-MS/O (an odor dilution technique), and heart-cut multidimensional GC-MS (heart-cut MDGC-MS) equipped with the polar (1D) and apolar (2D) capillary columns revealed seven sweat-like odor producing compounds: methyl-branched saturated and unsaturated aliphatic acids, such as 3-methylbutanoic acid (sweaty/rancid/cheese-like), 2-methylbutanoic acid (sweaty/rancid/cheese-like), 4-methyl-3-pentenoic acid (sweaty/urine-like/malodor in laundry), and (<em>E</em>)-4-methyl-3-hexenoic acid (sweaty/urine-like/malodor in laundry), as well as others, such as an unknown compound (sweaty), methyl (<em>E</em>)-4-methyl-3-hexenoate (sweaty/malodor in laundry/fruity), and <em>S</em>-methyl (<em>E</em>)-4-methyl-3-hexenethioate (sweaty/rubber). The reference substances were synthesized stereo selectively using for the identification procedures. In this study, (<em>E</em>)-4-methyl-3-hexenoic acid, methyl (<em>E</em>)-4-methyl-3-hexenoate, and <em>S</em>-methyl (<em>E</em>)-4-methyl-3-hexenethioate were identified for the first time in hop volatile oil.</p>
Highlights
Hop (Humulu slupulus L.) is essential material for beer production along with water, malted barley, and yeast, which act the characteristic hop aroma and bitter taste
The odor-active compounds contributing to the overall aroma of hops have been found by means of aroma extract dilution analysis (AEDA) (Ullrich & Grosch, 1987), an odor dilution technique for screening using gas chromatography-olfactometry (GC-O) (Steinhaus & Schieberle, 2000; Lermusieau, Bulens, & Collin, 2001; Steinhaus, Wilhelm, & Schieberle, 2007)
The concentrated volatile fractions were analyzed by gas chromatography-mass spectrometry/olfactometry (GC-MS/O), AEDA, and heart-cut multidimensional gas chromatography-mass spectrometry to identify target active compounds with a sweat-like odor by comparison with synthesized reference substances
Summary
Hop (Humulu slupulus L.) is essential material for beer production along with water, malted barley, and yeast, which act the characteristic hop aroma and bitter taste. Lermusieau et al (2001) reported 56 odor-active components in fresh hop pellets (Challenger and Saaz). Steinhaus et al (2007) characterized 38 odor-active compounds in five different hop varieties (Hallertau Perle, Hallertau Hersbrucker Spät, Slowenian Golding, Hallertau Smaragd, and US Cascade). Other than brief descriptions (Steinhaus & Schieberle, 2000; Lermusieau et al, 2001; Steinhaus et al, 2007), there are no detailed reports regarding the aroma components responsible for the sweat-like odor in hops, most of which may contribute to the overall aroma. The focus of this study is on the novel sweat-like-odor active compounds in Hallertau Perlehop volatile oil. The concentrated volatile fractions were analyzed by gas chromatography-mass spectrometry/olfactometry (GC-MS/O), AEDA, and heart-cut multidimensional gas chromatography-mass spectrometry (heart-cut MDGC-MS) to identify target active compounds with a sweat-like odor by comparison with synthesized reference substances
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