Rapid Determination of Ethanol in Food by Combination of Quinone-dependent Alcohol Dehydrogenase Reaction and Self-driven Coulometry

Abstract

A new method for determination of ethanol was developed by combining a quinone-dependent alcohol dehydrogenase reaction and self-driven coulometry and applied for determination of ethanol in food. Enzyme reaction was carried out in a mixture consisting of MacIlvaine buffer (pH 5.0), ubiquinone-0 (Q0), quinone-dependent alcohol dehydrogenase and a sample. An aliquot of the reaction mixture was then added to the self-driven coulometric cell to determine the amount of reduced Q0 by coulometry. In a range of 0.1 to 30% (v/v) of ethanol, the measured total charge was almost the same of the theoretical and correlated with the ethanol concentration with a correlation coefficient of 0.9997, suggesting that ethanol was measured without calibration. Ethanol concentration in twenty daily foods determined by this method were correlated with those determined by gas chromatography with correlation coefficient of 0.9991 and coefficient of variation of ten trials was below 2%. The measuring time in the self-driven coulometry was 1 to 5 min. After 100 trials of addition of a sample on the carbon-felt electrode in the self-driven coulometric cell, no effect on the total charge was observed. These results indicated that ethanol in food was rapidly determined by this new method. © 1995, Japanese Society for Food Science and Technology. All rights reserved.