Abstract
Aging or maturing of whisky, brandy and other distilled spirits after long storage is not fully understood to distillers or consumers. The stimulative taste of ethanol batches in the early periods of storage is lost after long storage. Although many chemists concerned with spirit distillery have investigated changes in chemical constituents during storage, a sufficient explanation does not follow from their research.
In the present study the liquid properties of aged spirits were investigated by nuclear magnetic resonance technique. The NMR spectrum of hydroxyl protons was measured on a Hitachi R-20 A (60 MHz) at -32 to 34°C. In aged spirits the NMR spectrum of hydroxyl protons was significantly broader compared with new spirits. There was a half band width increase in proportion to the length of storage. The effects of minor chemical components were slight on the NMR spectrum with aging. These experimental results indicated a decrease in the exchange rate of hydroxyl protons, formation of stable molecular clusters in which the migration of ethanol molecule was restricted and there was a decrease in monomeric ethanol, which produced a stimulative taste. Certain physicochemical properties of aged spirit found in this study agree closely with the desirable sense of smell and taste.
