Changes in the macroscopic cluster size of liquor with storage

Abstract

We defined the macroscopic cluster size of liquor in order to discuss quantitative changes in solution structure with storage. We determined the size of three kinds of clusters in malt whiskies. First, NMR spectra were measured for aqueous ethanol solutions, and the population fractions defied by eq.(3)were calculated from the changes in the proton chemical shifts with increases in ethanol concentrations. Next, IR spectra were taken for the gases evaporated from the whiskies and aqueous ethanol solutions. Comparisons between the band areas from the whisky and those from the aqueous ethanol solution made it possible to obtain the ratios of the water and of the ethanol molecules evaporated from the two solutions. Finally, the population fractions for aqueous ethanol solutions were converted into those for the whiskies by these ratios according to eq.(12), and the sizes of the three clusters were calculated for each whisky. The results differ from previous ones: specifically, as the period of storage becomes longer, the size of the water clusters increases while that of the ethanol clusters decreases and that of the water-ethanol clusters is almost constant.