Friday, May 01, 2009

Fermenting and Distilling

Most alcoholic drinks contain ethanol, which also called ethyl alcohol. One of the common processes in the production of alcohols is fermentation.

Fermentation is the use of yeast to convert glucose (or sugar solution) into alcohol (specifically ethanol) and carbon dioxide.

Glucose + Yeast -> Ethanol + Carbon dioxide

** Sugar canes are among the crops used for ethanol production.

The zymase enzyme in yeast is the catalyst for the reaction as it carries out anaerobic respiration on glucose, thus changing it into ethanol and carbon dioxide. Fermentation stops when the ethanol gets too concentrated and denatures the enzymes.

The resultant carbon dioxide gas escapes into the air, leaving a mixture of ethanol and water. Ethanol can then be separated from the mixture by fractional distillation.

Fractional distillation is based on the concept that two liquids have different boiling points.

The mixture of ethanol and water is heated until it boils. The liquid with the lowest boiling point boils first and vapourises.

The gas vapours are cooled in the condenser until the temperature falls below the boiling point. When they are condensed back into liquid, they are collected in a container.

The collected liquid is called the distillate, which means it has been distilled.

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