determination of ethanol in beer using a bioelectrochemical cell

A dye‐linked alcohol dehydrogenase from Rhodopseudomonas acidophila, with a very high affinity for ethanol, has been incorporated into a bioelectrochemical cell and used for determining the concentration of ethanol in beer. The cell measures as little as 5–25 μg of ethanol, with a coefficient of variation of 3·1%. A wide range of beers and beer distillates have been used and the non‐volatile components have been shown not to interfere with the assay. Other primary and secondary alcohols and aldehydes which are substrates for the enzyme do not contribute to the output of the cell at the concentrations in which they are normally encountered in beer. Values obtained using the cell correlate closely with those determined using a commercial test kit which incorporates a NAD‐linked alcohol dehydrogenase, but results are obtained more rapidly and economically.