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Fermentation
The cooled wort is collected in the fermenting vessel at a temperature which will vary depending on the ambient temperature and the strength of the beer being brewed. Usually between 16 and 20°C.
Prior to the addition of yeast the gravity of the wort is adjusted using cooled liquor from the hot liquor tank.
At Broughton, just as each beer has its own recipe of coloured malts and blend of hops, each beer is collected in fermentor at its own “original” or starting gravity. The original gravity (OG) is a measure of the amount of the various sugars extracted from the malt and dissolved in the wort. This is important since it has a bearing on the flavours developed in the beer during fermentation.
Yeast is added at this point.
Yeast is a living organism and like all living organisms requires a source of energy for its life processes.
The yeast obtains this energy by breaking down the sugars into alcohol and carbon dioxide.
During the course of a fermentation the yeast will use this energy to multiply itself by a factor of 4 or 5.
In common with most UK breweries Broughton use a top fermenting yeast.
This means that as the yeast ferments it tends to rise to the surface forming a thick head on the surface of the fermenting beer.
When fermentation is judged to be complete, ie the correct amount of sugar has been converted into alcohol, the vessel is cooled using refrigerated water pumped through cooling panels immersed in each fermentor.
At this point the excess yeast is skimmed off and collected in a large trough.
This yeast is allowed to settle then decanted into square bins which are stored in a refrigerator at 0-2°C.
At this temperature the yeast will keep in a healthy condition for up to three weeks.
Normally, however, the yeast skimmed one week is pitched into a new brew the following week.
After fermentation the beer is allow to cool and remains in the fermenting vessel for a total of 7 days. This allows a certain amount of maturation and settling of yeast left in suspension after skimming.
At this point the beer is racked into tanker, for transport to the Bottling plant, or into cask as real ale.
