Abstract
After fermentation followed by distillation, whiskey is stored in oak barrels for several years to some tens of years, a process known as aging. During the aging process in oak barrels, colorless distillates turn to amber distillates and the sharp or raw odor typical of fresh whiskey distillates is modified to a rounded, soft, and mellow aroma. Various compounds such as fragrances and polyphenols in the oak are extracted by the whiskey, while water or unpleasant odors pass out of the barrels through the boards. Aging of whiskey increases the potentiation of the response of GABAA receptor, a main inhibitory neurotransmitter receptor and the target of mood-defining drugs such as tranquilizers, sleeping drugs and anesthetics. Aging of whiskey also increased 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity, i.e., antioxidative activity. The increase of acidic and phenolic components in whiskey, which is gained in oak wood barrels during aging, shifted OH-proton chemical shift values toward the lower field proportionally, suggesting that these compounds strengthened the hydrogen-bonding structure of water-ethanol in whiskey and may make the whiskey taste good. These changes of minor components in whiskey during aging might improve the flavor and taste and make aged whiskey highly valued.
Keywords: Aging, anti-oxidative activity, GABAA receptor, hydrogen-bonding, whiskey
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