Progressive increase in minimum proton exchange rate with maturation of liquor

Proton exchange rate measurement was carried out by 17O-NMR spectroscopy using mother liquors of malt (aged for 0 to 15 years) and grain (aged for 0 to 8 years) whiskies, and of shochu (aged for 1 to 21 years) and awamori(aged for 0 to 10 years) of Japanese traditional spirituous liquor, and commercially available whiskies (aged for 5 to 21 years) and brandies (aged for 5 to 45 years). Through the examination of proton exchange rate based on 17O-NMR half width - pH curve plots, it has been found that the minimum proton exchange rate increases as the period of maturation of liquor becomes longer.