Yeast and Fermentation

Posted: 17 April 2012

For those of us that were busy cooking Sunday lunch this weekend the Radio 4 Food Programme made interesting listening as it was dedicated to the ancient and mysterious craft of fermentation – they described it as harnessing the power of microbes to make food more delicious rather than allowing it to decompose and go rotten.

There is a suggestion that currently a third of all food have undergone some form of fermentation (drinks are a sub set of foods)

Whilst this programme covered all elements of fermentation with naturally available yeasts and bacteria from the development of chutneys and fermented vegetables through to sake, malt drinks and even milks and yoghurts fermentation is a critical part of the brewing process.

The production of beer is similar to the production of sake as outlined on Radio 4.

In essence brewing is the conversion of the starch that is naturally available in the malted barley into alcohol. The starch is converted into sugars during the mashing process which is very temperature dependent in order to achieve the desired sugar mix to give both fermentable sugars and the body of the beer. Unlike in the programme no enzymes are added since these are contained within the malt and just need to be activated by the increase in temperature.

The sugars are then converted into alcohol and carbon dioxide during the fermentation stage by the addition of yeast.

A brewer’s yeast strain is a very carefully controlled material since it gives the beer much of its characteristic flavour and the reliable fermentation that ensures a consistency of product.

We have our own ale yeast strain that can be traced back through the history of the brewery which is used to produce the whole range of our ales. We also have a number of lager yeast strains that are used to brew a wide range of lagers, not quite from A to Z but certainly from Asahi to Sunlik.

As I have suggested it is critical to care for these yeasts and keep them separate and so we have a small scale plant where we can grow them up from pure cultures and are typically producing 2 new yeast cultures a week. We are meticulous at both maintaining records of traceability and at plant hygiene to ensure there is no possibility of one yeast mixing with another.

As was suggested in the programme fermentation is both a fascinating process and more importantly produces some wonderful flavours and I hope you agree it is something that we are good at.




Stewart Tricker - Senior Brewer