Starting out in the world of home brewing can be quite overwhelming to being with, what with all the acronyms that you're sure mean something but don't have a clue what. Here is a brief guide into what they all mean and how they are used in homebrew recipies.
ABV - Alcohol by volume, this is a standard measure of how much alcohol in present in a given volume of an alcoholic beverage. Basically the higher the number the stronger the beer and the more likely you are going to suffer from the classic loss of leg function.
OG and FG - Original Gravity and Final Gravity, the measure of the relative density of the liquid. This number is dependant on the quantity of sugar within you liquid. This is typically measured using a hydrometer. The OG is measured before the fermentation and the FG is measured after fermentation following the equation below to give you a value of how much sugar has been converted to alcohol by the yeast.
% ABV = ((Original gravity - Final gravity) / 0.75) x 100
IBU - International Bitterness Units. This unit is the magical number that provides a method of quantifying how bitter the beer is, related to how much iso-alpha acid (isomerised alpha acid) is present in your wort. Different hops have different alpha acid contents and therefore different battering powers. The IBU can loosely be calculated from the following equation:
IBU = (weight of hops x alpha acid % x utilisation %) / volume brewed x 10
% utilisation is a very vague subject but basically it means the amount of iso-alpha acid that we get from the hop, otherwise known as the hop extraction efficiency.
SRM - Standard Reference Method. One of several systems used to describe and specify beer colour in a less subjective way. Basically the higher the number the darker the beer, for example a pale larger would have a SRM of ~2 and a stout would have a SRM of ~30.
The most important things for the burgeoning homebrewer to pay attention to are the original gravity (OG), final gravity (FG) as this will allow you to determine when fermentation has finished as well as calculate the % ABV.
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