Aging of Whiskey Increases 1,1-Diphenyl-2-picrylhydrazyl Radical Scavenging Activity

1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity of Japanese whiskey after various
aging periods in oak barrels was measured to evaluate the antioxidative effects of whiskey. The
activity of the whiskey increased with the aging period with high correlation. The activity of various
types of whiskey was measured and shown to be correlated to the potentiation of the GABAA receptor
response measured in a previous paper. However, the fragrant compounds in the whiskey which
potentiated the GABAA receptor response had low DPPH radical scavenging activity, while phenol
derivatives had high radical scavenging activity. The whiskey was extracted by pentane. The aqueous
part showed the scavenging activity, whereas the pentane part did not. Thus, both the DPPH radical
scavenging activity and the potentiation of the GABAA receptor response increased during whiskey
aging in oak barrels, but were due to different components. The whiskey protected the H2O2-induced
death of E. coli more than ethanol at the same concentration as that of the whiskey. The changes
that occurred in the whiskey during aging may be the reason aged whiskies are so highly valued.
Keywords: Aging of whiskey; antioxidant; DPPH radical; polyphenol; radical scavenging