Identification of the Compounds Responsible for the Sweat-Like Odor in Hop (Humulus lupulus L.) Volatile Oil

Abstract

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 ( Humulus lupulus 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 ( E)-4-methyl-3-hexenoic acid (sweaty/urine-like/malodor in laundry), as well as others, such as an unknown compound (sweaty), methyl ( E)-4-methyl-3-hexenoate (sweaty/malodor in laundry/fruity), and S -methyl ( E)-4-methyl-3-hexenethioate (sweaty/rubber). The reference substances were synthesized stereo selectively using for the identification procedures. In this study, ( E)-4-methyl-3-hexenoic acid, methyl ( E)-4-methyl-3-hexenoate, and S -methyl ( E)-4-methyl-3-hexenethioate were identified for the first time in hop volatile oil.