Yeast & Fermentation
A great discovery and an essential ingredient in beer. At Cromarty we harvest yeast from a previous batch which then gets pitched into the next. We have conical bottoms on the fermentation vessels which allow us to easily crop the correct section of yeast.
Once the wort has been run through the heat exchanger to cool it to fermentation temperature (about 20c) it is oxygenated and pumped into the fermentation vessel. Oxygen is added at this stage as the yeast cells require it to grow and reproduce during the aerobic growth phase which then in turn ensures a healthy fermentation. This phase is usually about 12 hours and is also known as the lag phase. Once this is completed the yeast start to convert the sugars present in the wort to CO2 and Alcohol. Yeast is pitched between 6,000,000 cells to 18,000,000 cells per ml of wort depending on the beer being made, that’s about a total of 20,000,000,000,000 cells per brew – a lot of yeast!
Active fermentation is usually finished within 5 days and after sufficient checks the temperature of the beer is then cooled to allow the yeast to settle for cropping. Depending on the beer being produced we sometimes add more hops at this point to emphasise hop aroma and flavour, this process is known as Dry-hopping.