Brewing, as it turns out, is a four dimensional world. While many an Upland drinker swears that a limited Seasonal or a Year-round favorite propels them right into hyperspace, that’s not really what we’re talking about on the Sorter page.
The Sorter lines-up 20 of our fine quaffs by the four key metrics beer aficionados pay the most attention to. Most of this is from the Wikipedia – click the abbreviations to go to the full article.
ABV: Alcohol By Volume
In the brewing process, yeast is added to a sugary solution (usually fruit juice or malted barley) where over fermentation the yeast organisms consume the sugars and produce alcohol. The density of sugar in water is lower than the density of alcohol, therefore by using a hydrometer to measure the change in specific gravity (SG) of the solution (before and after fermentation) the volume of alcohol in the solution may be calculated.
IBU – International Bittering Units
The International Bittering Units scale, or simply IBU scale, provides a measure of the bitterness of beer, which is provided by the hops used during brewing. Bittering units are measured through the use of a spectrophotometer and solvent extraction.
The bittering effect is less noticeable in beers with a high quantity of malt, so a higher IBU is needed in heavier beers to balance the flavor. For example, an Imperial Stout may have an IBU of 50, but will taste less bitter than an English Bitter with an IBU of 30, because the latter beer uses much less malt than the former. The technical limit for IBU’s is around 100; some have tried to surpass this number, but there is no real gauge after 100 IBUs when it comes to taste threshold.
SG – Specific Gravity
As fermentation progresses the yeast convert sugars to carbon dioxide, ethanol, more yeast and flavor producing compounds. The decline in the sugar content and the presence of ethanol (which is appreciably less dense than water) both contribute to a lowering in the specific gravity of the wort so that the formulae relating sugar content and specific gravity no longer apply. Nevertheless, by monitoring the decline in SG over time the brewer obtains information about the health and progress of the fermentation and determines that it is complete when gravity stops declining. A gravity measurement taken at this time compared to the original gravity reading can be used to estimate the amount of sugar consumed and thus the amount of ethanol produced. Specific gravity is measured by a hydrometer, pycnometer or oscillating U-tube electronic meter.
Gravity (specific gravity) measurements are used to determine the “size” of the beer, its alcoholic strength and how much of the available sugar the yeast were able to consume (a given strain can be expected, under proper conditions, to ferment a wort of a particular composition to within a range of attenuation, that is, they should be able to consume a known percentage of the extract).
SRM – Standard Reference Method
The Standard Reference Method is a system modern brewers use to measure color intensity, roughly darkness (but see Tristimululs Color below), of a beer or wort. The method involves the use of a spectrophotometer or photometer to measure the attenuation of light of a particular wavelength, 430 nanometers, as it passes through a sample contained in a cuvette located in the light path of the instrument.
SRM/Lovibond Example Beer color EBC 2 Pale lager 4 3 German Pilsener 6 4 Pilsner Urquell 8 6 12 8 Weissbier 16 10 Bass pale ale 20 13 26 17 Dark lager 33 20 39 24 47 29 Porter 57 35 Stout 69 40 79 70 Imperial stout 138
