Beer Anatomy

Beer Anatomy

Before we begin to assemble a beer, it might be advantageous to quickly dissect one. Beer is a solution of water and alcohol and with carbon dioxide, flavoured and coloured with small traces of carbohydrates, proteins, minerals, melanoidins, and thousands of different aromatic compounds acquire from the malt, hops, and yeast. It is this wide range of compounds, in specific quantities, which provides each style of beer with a unique taste.


The factors below are the most widely used factors for quantifying beer, most of which can be precisely calculated and are therefore used to examine beer for quality control by particular agencies. As brewers, we will need to understand these numbers and their relevance to describe beers and create recipes based on amounts of ingredients and various other variables. Government rules and regulations, such as the European Brewery Convention define the procedures and standards for analysing beers, measurement units, and other specifics.


This refers to the density of wort, a way of calculating the amount of dissolved substances, largely sugars that will be converted into alcohol, as well as various unfermentable carbohydrates. It acts as an early gauge of the strength of the final brew. There are two different systems used to convey this density: degrees Plato (°P) and original gravity (OG).

Plato describes gravity as a percentage by weight. A 10°P wort will have 10 percent by weight of dissolved matter. Degrees Balling is method used prior to Plato’s. As Balling was Czech, his name is still used today in Czech brewing.

Original gravity is the second measurement and is almost identical to specific gravity, however the density is expressed as a ratio relative to pure water; 1.040 wort is 1.040 times as dense as pure water.

Occasionally the decimal point is absent for convenience sake. Make sure you know that when doing calculations with OG, the “1” and decimal point at the start are not included in the maths; if included the calculation will not work. A loose rule of thumb is that the significant digit of an OG is an estimation of the alcohol content (1.050 = 5.0% alcohol/volume), though this is not always true and affect but a number of different variables.

Gravity is normally calculated using a hydrometer, which is simply a weighted glass tube with a scale located on the inside which stops at a level relative density of the liquid being measured. The denser, the further up the scale the hydrometer floats. Some brewers use a fractometer instead, a less messy alternative which provides immediate results. A fractometer measures original gravity through the refractive properties of sugar and is mainly used to measure wort as alcohol warps the readings, making it ineffective at measure the OG of beer.

Terminal Gravity

Terminal gravity is conveyed using the same units as original gravity, however it is a measurement of how much gravity is left after fermentation has finished, using terminal gravity the alcohol content of the finished beer can therefore be determined.


Simply put, this is the percentage of ethanol within in the finished beer. The current international criterion is percent by weight, and that’s what we’ll be using here.

Alcohol content is calculated only through extracting it out of the beer and then weighing it. Therefore the majority of small-scale brewers are only able to make an approximate, through the original versus terminal gravities. To do this, a “potential alcohol” scale is needed. A value is taken both prior to and after fermentation. The latter is subtracted from the prior, and the result is a surprisingly accurate estimation.

Potential alcohol and original gravity scale:


This is a solitary value of lightness/darkness acquired by putting a sample of beer into a spectrophotometer and calculating the percentage of absorption at a particular wavelength. During the nineteenth century, Joseph Lovibond developed the first beer colour measure using a sequence of coloured glass disks. Later, the spectrophotometric technique was developed and soon replaced Lovibond’s method, however it was found that the findings from both methods matched up very closely, so occasionally you will see beer and malt colour in degrees Lovibond. U.S. and European standards vary slightly in thickness of the cuvette used to hold the sample beer—half an inch in the U.S. Standard Reference Method (SRM), and 1 centimetre is used by the European Brewery Convention (EBC). Due to these differences, the same beer measured by the EBC method will have a value nearly double that of the SRM.

Expanding from just light and dark, beer may differ in its tint from reddish to yellowish. Techniques utilising multiple colours, known as tristimulus, are used to assess the colour of a beer in a way which is similar to that of your eyes, however these are rarely used.

The graphic above shows the range of colours in beer and their corresponding Standard Reference Method number.


This is determined though a chemical test which utilises some moderately dangerous chemicals as well as an ultraviolet spectrophotometer. The universal criterion of Bitterness Units (BU) relates to parts-per-million (mg/L) of isomerized alpha acid in the completed beer and this relates directly to the recognized bitterness you get when you drink beer.

Also, there is a European version (EBU) of the measurement which provides marginally different numbers, however, the difference is very small and so these systems can be thought of as the same. For the majority of homebrewers a calculated BU number is used, this can vary significantly from calculated numbers, depending on a number of variables, particularly at the higher end. For mega-hoppy beers such as double IPAs, there are doubts surrounding the reliability of the standard assays.


This is a gauge of how complete the fermentation process is. It can be estimated by deducting the final gravity from the original gravity, and then dividing the number produced by the original gravity, presents a percentage. For example, if a 1.650 wort finishes at 1.020, then the 20 is subtracted from the 65, which gives 45, divided by 65, which equals 69 percent. This is known as apparent attenuation, and it is incorrect to some level due to the lower density of alcohol which alters the reading, and therefore the beer appears to be more attenuated than it really is. With very dry beers, apparent attenuations higher than 100 percent are attainable. In order to calculate the real attenuation, the alcohol needs to be extracted from the beer and measured, then put into the calculation. The reasons are clear why most small brewers use apparent attenuation.

The degree of attenuation can be altered by a number of different variables. Ingredients such as sugar or honey are completely fermentable, and so they raise attenuation. Mashing methods also affect the fermentability of the wort; this is an additional tool the brewer can utilise in order to control the sweetness or dryness of the beer. Elite methods such as fungus-derived enzymes are needed to brew light, dry, and low-carb beers. Lastly, yeast strain and fermentation environments have an effect on attenuation that can be hard to forecast.

High apparent attenuation percentages signify a dry beer, whilst low apparent attenuation percentages signify a sweet beer.


We’re finished with numbers for now, but there are many additional qualities to beer which are either difficult or impossible to measure. Body and texture are significant in beer, as is head retention; all of these can be influenced through the beers protein structure. Balance is a word used to depict the way different flavours and aromas cooperate, particularly hops and malt, but it’s not necessarily just those two; other flavours which come into the forefront include roastiness, acidity, and fruitiness. The word contrast, better sums up the vibrant collaboration of elements that add interest as you drink.

Drinkability, an overused, veteran phrase used by corporate brewers as poor justification for how little they have to offer drinkers is, however a significant feature for beer as few can create a business out of beers which are merely sippable. Complexity is a clear term which includes many factors, and is always sought-after by brewers, even in the lightest, most refreshing beers.

Outside of all that is something which I refer to as delightfulness, an amalgamation of everything delicious, magical, and intense in a beer. It’s an extremely subjective and private measure but one of the most important.