Brewing Series: Making Sense Of Acronyms In Brewing Like ABV, OG and IBU

Brewing does have its own language and you may wonder what many of the acronyms mean on a beer label. We’ve come up with some simple answers to help make sense of what often seems impenetrable language. It even reminded us of what the meanings are because even though there are strict definitions the significance varies between producers.

The acronyms that define the beer that is in your bottle are ABV, OG, IBU etc. All these acronyms refer to a standard that defines the beer or lager. In some cases it may be part of the bigger picture when it comes to taxing alcohol as with the ABV and for that matter the meaning of ‘proof’. 

ABV (Alcohol by Volume)

The subject of alcohol by volume is usually related to ales whilst proof is used in spirits. We did a large article on alcohol as ethanol when discussing regulations in the USA and explaining what the different forms between the two were.

The ABV is mandatory on a beer label in the USA and Europe. It means alcohol by volume and it is a standard measure of how much alcohol is contained in a given volume of an alcoholic beverage. For regulatory and analytical purposes it is:

• the number of milliliters (mL) of pure ethanol present in 100 mL of solution at 20°C (68°F).

Note that it uses S.I. units and is measured at a precise temperature which is taken to be a typical room or ambient temperature.

It is also quoted as a percentage so that mL value of pure ethanol is multiplied by a hundred. A 4 per cent ABV translates into 4 mL of pure ethanol in 100 mL of beer say.

It also refers to ethanol rather than alcohol because ethanol is the chemical compound that is measured precisely and the one that makes you drunk for want of a better explanation. It is also the compound that is measured for tax reasons. Ethanol is an alcohol but alcohols in chemistry terms tend to embrace a host of compounds that might include isopropanol, methanol amongst many others. These all have at least one hydroxyl group (-OH) as a functional group on the molecule. Alcohols then are many and varied but in most consumer parlance we usually take alcohol to mean ethanol when thinking about a beer or lager.

For the drinker the ABV is often the marker of choice. The higher the ABV the more likely the impact of ethanol will have on flavour and on our state of perception after a few pints. A  beer or lager will have an ABV of somewhere between 4 and 5 per cent ABV. Most are in this range. Stronger beers like Belgian beers and stouts will range from 6 per cent right up to 12 per cent ABV. 

The unit number is globally recognised.

Specific Gravity (SG)

Specific gravity is a ratio of the density of a sample to that of water. It usually has to be defined for a specific temperature and pressure because the density of any liquid is affected by these two parameters. Those values are always 1 standard atmosphere at a temperature of 20ºC or 68ºF.  

OG (Original Gravity)

Some beer labels have the OG or Original Gravity printed. It has more significance for the brewer than the drinker but it is a useful value to know. The original gravity gives us a measure of how the starting material or feedstock for a beer fermentation will translate into an ABV. That starting material is wort.

The OG is defined as the mass in grams of sugar in 100 grams of wort. It has the symbol (°P). The value is also established using the Plato scale. If you work in the soft drinks industry then you are often likely to use Brix rather than Plato.

The original gravity has the same meaning as original extract (OE).

The analyst at the brewery will establish the OG so as to estimate the potential amount of ethanol that can be generated from the fermentation. 

A variety of methods exist to measure OG usually by measuring specific gravity. It can involve a refractometer, density meter or even a viscometer. The measures are defined in standards.

IBU (International Bitterness Units)

The IBU value is rarely seen on a beer label but it is a measure of the bitterness of the beer. Some US beer labels now define it because it gives the drinker an idea of the sensory quality of the beer.

The higher the IBU the more bitter it is but it has no bearing on whether the beer is high quality or not.

It is a scale which ranges from zero (0) up to 120 in most cases but can be higher. Some beers are so bitter that have been recorded at 2,500 IBUs which is extreme in the least. If the beer was zero IBU it would be perceived by the drinker to have no bitterness whatsoever. A value of 120 would mean it was very bitter but drinkable. Most beers have a bitterness rating of between 15 and 80.

It is based on a chemical measurement of the amount of compounds that contribute bitterness which are isomerized and oxidized alpha acids, polyphenols, and some other bittering chemicals. Most of the bittering compounds come from added hops and a small contribution will come with the grain and malts used in mashing but its almost insignificant. To make it an analytical measure it is defined as the number of parts per million of isohumulone which is found in beer. That compound comes from hops.