The process of brewing your favourite ale is part art, part science, and although the basic ingredients are simply barley, water, hops and yeast, the number of different styles of beer that can be produced is huge! Here is a brief explanation of the process that an average beer goes through in order to produce the pint that ends up in your glass.
The process starts with malted barley, which is simply barley that has started to germinate, which releases the enzymes required to convert the starches in the grains into the sugars needed in the fermentation process. Malting is done by soaking the barley in water to begin the germination, and then drying it, often by roasting in a kiln. Different roasting times can produce malts of different flavours and colours, which will vary the colour and flavour of the final beer. The malted grains are then milled ready for the mashing process.
The crushed malted barley is put into a large vessel called a mash tun, and mixed with hot water, which allows the enzymes in the grains to begin to convert the starches into sugars. This mashing process generally takes around a couple of hours, and the temperature is very carefully controlled. The resulting liquid, which is high in sugar, is filtered out of the mash tun (lautered). This liquid is known as wort. Sometimes additional water is sprayed over the grains remaining in the mash tun, to extract more sugars from the grains (a process known as sparging).
The wort is then transferred into a vessel known as a copper, and hops, often in pellet form, are added. The hops add bitterness and aroma to the beer, with different types of hops providing different results. The mixture is boiled, sometimes for as long as 2 hours. At the end of the boiling process, further hops are sometimes added – a process called ‘late hopping’ – immediately before the wort is cooled, to add further aroma to the beer. The hops are then removed, and the wort cooled to the correct temperature for fermentation by passing it through a heat exchanger.
After cooling, the wort passes into the fermentation tank, and yeast is added to begin the process of turning the sugars in the liquid into alcohol and carbon dioxide, transforming the wort into beer. Ales are generally fermented at a slightly higher temperature than lagers, using yeast that foams on the top of the liquid (top fermenting). Yeasts used in the production of lager are generally bottom fermenting, and act at cooler temperatures.
Towards the end of the fermentation process the activity of the yeast slows, and the beer then goes through a period of conditioning. It is sometimes moved to a separate tank, or directly into the final cask/bottle for this conditioning process (hence the term cask/bottle conditioned ale), where the beer is left to age for a period of time anywhere between a week to a few months. During the period of conditioning, some of the chemical compounds are processed and unwanted flavours cleared out, and the beer settles. Sometimes this process is helped along by chilling the beer; this is known as ‘cold conditioning’.
Sometimes a separate filtration is performed through a physical filter to clear the beer and remove any remaining sediment before transferring to the bottle or keg. This stops the conditioning process, and removes all the yeast and other debris from the beer. Alternatively beer is sometimes treated by dropping finings or other agents through the beer to remove the sediment and so on as they settle – the beer is then said to have ‘dropped bright’.
The way each of these processes is carried out contributes to the final style and taste of the beer. The roasting of the barley, the variety of hops and when they are added, the type of yeast used, the conditioning process and where this is done, and whether the beer is filtered all have an effect on the final product, leading to the enormous variety of types of beer available.