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DIFFERENTIAL SCANNING CALORIMETRY (DSC) STUDIES ON THE FREEZING PROCESSES OF WATER‐ETHANOL MIXTURES AND DISTILLED SPIRITS
Author(s) -
KOGA KUNIMASA,
YOSHIZUMI HAJIME
Publication year - 1979
Publication title -
journal of food science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 150
eISSN - 1750-3841
pISSN - 0022-1147
DOI - 10.1111/j.1365-2621.1979.tb06444.x
Subject(s) - distilled water , differential scanning calorimetry , chemistry , ethanol , freezing point , chromatography , analytical chemistry (journal) , thermodynamics , organic chemistry , physics
ABSTRACT DSC measurements of the freezing of water‐ethanol mixtures in various ethanol concentrations were made in a temperature range from +20° C to ‐160°C. One exotherm was observed in the freezing process of each mixture. The freezing point, heat associated with the freezing process and kinetic constant of freezing (k f ) were determined over the entire range of the ethanol concentration from the DSC thermogram. Log k f was plotted as a function of the reciprocal of the absolute temperature (T ‐1 ) of the mixtures. The freezing process of the mixtures in an ethanol concentration of 0˜75 (V/V)% obeyed first order kinetics but at a concentration above 75%, the freezing process did not do so. The slope of log k f versus 1/T plots (d log k f /dT ‐1 ) of the mixture at the concentration below 75% was determined. The concentration below 75% was divided into four ranges (0˜18.5%, 18.5˜40%, 40˜60%, 60˜75%) from a variation in the slope of the linear plots. The results of the, DSC measurements of freshly distilled spirits (raw whiskey from barley malt and grain spirits) coincided with those of simple water‐ethanol mixtures. It is considered that the freezing reaction of distilled spirits proceeded by the same mechanism as that of the simple mixture of the corresponding ethanol concentration. Structures of distilled spirits as a function of ethanol concentration were discussed in terms of the interaction of water and ethanol molecules.