Methods for determining ethanol in beer

Ethanol, together with water and carbohydrates, is one of the main components of beer. Its concentration ranges from 0.05% (v/v) in alcohol free beers to about 12.5% in the strongest ones. An accurate and rapid determination of ethanol in beer is important for regulatory applications and process control in brewing industries, and on-line continuous monitoring is often desired. Classical methods such as refractometry, densitometry, or redox titration of the distilled sample, as well as gas chromatography, are routinely used in industry and in government control laboratories, but they are time- and labor-consuming procedures. To replace these techniques efforts have been made to develop methods with low-cost instrumentation and/or without complex sample pre-treatment. Biosensors based on alcohol oxidase and alcohol dehydrogenase enzymes have been fabricated and successfully applied to ethanol determination in alcoholic beverages. Furthermore, infrared spectroscopy in the mid- and near-infrared region as well as techniques such as fl ow injection have provided interesting possibilities to also automate ethanol determination.