As promised in my previous post, below I’ve outlined (with a lot of help and pictures from a tour around St Austell Brewery) the beer brewing process.
Stage 1 – The mill
St Austell Brewery uses the tower brewing system over five floors.
At the very top, 4 tonnes of malt from Maris Otter barley is crushed into a coarse flour known as grist in the mill.
The wooden mill on the right dates back to 1887 – while there is nothing wrong with it, it is a little slow so St Austell Brewery have installed a more up-to-date version (red and green steel on the left)
Stage 2 – The mash tun
On the next floor down, water (known as liquor) from St Austell Brewery’s own private well is mixed with the grist to make a thick porridge called the mash.
During this process, enzymes from the malt convert the starch into sugars and the resulting sweet liquid (known as wort) is filtered out for the next stage of the brewing process.
Stage 3 – The copper
In the copper, hops are added to the wort and the resulting mixture is boiled for 75 minutes. This sterilises the liquid and allows the flavour aromas to develop. Depending on the style of beer, different hops from around the world may be added.
Due to the high temperature, a lot of the liquid evaporates at this stage, taking some of the hoppy flavours with it so the wort is then passed through a second bed of hops to inject more of the desired flavour characteristics.
It is then rapidly spun to create a whirlpool allowing excess sediment to sink to the bottom to be removed. The resulting liquid is then cooled to below 15°c ready for the addition of yeast, which would die at too high a temperature.
Stage 4 – Fermentation
At this stage, brewers yeast is added to feed on the sugars in the wort, converting them to alcohol and carbon dioxide. During this process a frothy head forms on the surface of the beer (this is known as ‘top fermenting’) which is removed towards the end of the fermentation ready to be used again.
Stage 5 – Racking
After a few tests in the laboratory, the brew is ready to be filled into casks where secondary fermentation occurs adding a little spritz to the resulting beer.
While I haven’t gone into the nitty-gritty science, I hope this provides some insight into the world of brewing… Now you know how much love goes into that pint you’re sipping!