Hydrogen-bonding in water-ethanol solution and alcoholic beverages

The effects of solutes on the hydrogen-bonding structure of water-ethanol were investigated in water-ethanol solution on the basis of H-1 NMR chemical shifts of the OH of water and ethanol. It was found that the hydrogen-bonding structure of water-ethanol is strengthened by acids or (poly)phenols. Not only acids (H+ and HA: undissociated acids) but also bases (OH- A(-): conjugate-base anions from weak acids) had the effect of strengthening the hydrogen-bonding structure of water-ethanol. Alcoholic beverage is a kind of water-ethanol solution containing flavor and taste. The properties of the hydrogen-bonding of water-ethanol in alcoholic beverages have not been revealed sufficiently. We investigated what could affect the hydrogen-bonding structure of water-ethanol in alcoholic beverages on the basis of H-1 NMR chemical shifts and the Raman OH stretching spectra. It was also demonstrated that the hydrogen-bonding is strengthened by chemical components in real alcoholic beverages (whiskey, Japanese sake, shochu). It can be suggested that hydrogen-bonding donors as well as acceptors in alcohol beverages, which exist as the initial components or are gained later on, should cause a tight association between water and ethanol molecules.