Distilling terminology

Information provided by Bavarian-Holstein Partners.

Alcohol: A member of a class of organic compounds containing carbon, hydrogen and oxygen. Considered as hydroxyl derivatives of hydrocarbons, produced by the replacement of one or more hydrogen atoms by one or more hydroxyl (-OH) groups. Under the modern IUPAC (International Union of Pure and Applied Chemistry) naming system, the name given to an alcohol is derived from the parent hydrocarbon, with the final “e” changed to “ol”: thus methane-methanol; ethane-ethanol; etc. The principal alcohol in fuel and beverage use is ethanol, (otherwise known as ethyl alcohol). Murtagh & Associates, Alcohol Glossary

Aqua Vitae: Strong distilled alcohol; Latin for “water of life”.

Barrel: A liquid measure equal to 42 U.S. gallons, or 5.6 cubic feet. Or, a wooden container used for the aging and maturation of alcoholic beverages. Barrels used for whiskey maturation are made of oak wood, and have a capacity of about 52 U.S. gallons. Barrels may be used only once for aging bourbon whiskey, so there is a worldwide trade in used bourbon barrels for aging other alcoholic products such as Scotch whisky and rum. (Barrel measurements vary across different countries.) Murtagh & Associates, Alcohol Glossary

Carbon Dioxide: A colorless non-flammable gas. Composition CO2. It does not support human respiration, and in high concentrations it causes asphyxiation. It is approximately 1.5 times the weight of air, and tends to accumulate in floor drains, pits and in the bottoms of unventilated tanks. It is produced by various means, notably the combustion of fuels in an excess of air, and is a byproduct of yeast fermentation. It may be recovered from fermentations and compressed to a liquid or solid (“dry-ice”). Murtagh & Associates, Alcohol Glossary

Condensation: The process by which a gas or vapor changes to a liquid.

Distillate: A liquid condensed from vapor in distillation; a purified form, essence.

Distillation: The evaporation and subsequent collection of a liquid by condensation as a means of purification.

Ethanol: Otherwise known as ethyl alcohol, “alcohol”, “grain-spirit”, or “neutral spirit”, etc. A clear, colorless, flammable oxygenated hydrocarbon. Chemical formula: C2H5OH. It has a boiling point of 78.5°C in the anhydrous state. However, it forms a binary azeotrope with water, with a boiling point of 78.15°C at a composition of 95.57 per cent by weight ethanol. Murtagh & Associates, Alcohol Glossary

Fermentation: The anaerobic conversion of sugar to carbon dioxide and alcohol by yeast.

Fermenter: The vessel in which the process of mash fermentation takes place. The vessel may be fabricated from steel, fiberglass, etc., and is normally fitted with an internal or external cooling system for controlling the temperature of the fermenting mash.

Fusel Oil: Term used to describe the higher alcohols, generally the various forms of propanol, butanol and amyl alcohol, which are congeners, or by-products of ethanol fermentation – predominantly, iso-amyl alcohol. Their presence in alcoholic beverages is known to be a cause of headaches and hangovers. The fusel oils have higher boiling points than ethanol and are generally removed in the distillation process, to avoid accumulations in the rectifier. They may be subsequently added back into the anhydrous product for motor-fuel-grade ethanol. Murtagh & Associates, Alcohol Glossary

Heads: Term used to describe the impurities produced in ethanol fermentations (“congeners”), which have lower boiling points than ethanol. They include methanol and aldehydes. Murtagh & Associates, Alcohol Glossary
(Always the beginning phase of the distillation process.)

Tails: Term used to describe the alcohol that falls below 80 proof during the distillation process – also known as the end phase.

Malt: Barley grains, which have been steeped in water and then allowed to germinate. Drying the grains when the sprouts are about the same length as the grains normally halts the germination. At this stage, the malt (or “malted barley”) contains considerable amounts of alpha and beta amylase enzymes, which can saccharify the barley starch and other additional starch in a mash, to yield fermentable sugars. (In Scotland, the drying may be done by exposing the malt to a flow of peat smoke. This imparts a smokey odor to the malt.) Malt is used in whisky production, mainly for its contribution to product flavor, while in fuel-ethanol production the necessary saccharifying enzymes are normally derived from microbial sources. Murtagh & Associates, Alcohol Glossary

Mash: A mixture of milled grain or other fermentable carbohydrate in water, which is used in the production of ethanol. The term may be used at any stage from the initial mixing of the feedstock in water, prior to any cooking and saccharification, through to the completion of fermentation, when it becomes referred to as “beer”. Murtagh & Associates, Alcohol Glossary

Potstill: A simple batch distillation unit used for the production of heavily flavored distillates for beverage use. It consists of a tank, (which is heated either by an internal steam coil, or by an external fire), and an overhead-vapor pipe leading to a condenser. It may be used in the production of heavily flavored rums and whiskies. Murtagh & Associates, Alcohol Glossary

Alembic: The traditional pot still that requires several cycles of distillation in order to refine the alcohol to the desired level.

Reflux: This still differs from the alembic in that multiple distillations occur in one single cycle. The addition of a column with bubble plates (?) between the condenser and pot allows vapor to condense and trickle back down to be distilled once again. Thus, the vapor is repeatedly cleansed and the resulting purity from one cycle is much higher than that from an alembic.

Proof: A measure of the absolute-ethanol content of a distillate containing ethanol and water. In the U.S. system, each degree of proof is equal to 0.5 per cent of ethanol by volume, so that absolute ethanol is 200° proof. In the Imperial system “proof”, (or 100° proof), is equal to 57.06 per cent ethanol by volume, or 48.24 per cent by weight, while absolute ethanol is 75.25 over proof, or 175.25° proof. Murtagh & Associates, Alcohol Glossary

Reflux Ratio: The ratio of the amount of condensate being refluxed to the amount being withdrawn as product. Generally, the higher the reflux ratio, the greater is the degree of separation of the components in a distillation system. Murtagh & Associates, Alcohol Glossary

Saccharification: The process of converting a complex carbohydrate, such as starch or cellulose, into fermentable sugars such as glucose or maltose. It is essentially a hydrolysis. The process may be accomplished by the use of enzymes or acids. Murtagh & Associates, Alcohol Glossary

Stripping Column: The portion of a distillation column below the feed tray, in which the descending liquid is progressively depleted of its volatile components, by the introduction of heat at the base. Murtagh & Associates, Alcohol Glossary

Wort: The solution of grain sugars strained from the mash tun. http://www.abdi.org/Beer%20Terminology.pdf

Yeast: Any of certain unicellular fungi, generally members of the class Ascomycetaceae, (although a few are members of the class Basidiomycetaceae). Many types of yeast are capable of producing ethanol and carbon dioxide by the anaerobic fermentation of sugars. Yeasts are composed of approximately 50 per cent protein and are a rich nutritional source of B vitamins. Murtagh & Associates, Alcohol Glossary