Yeast, Yeast, Yeast!

For this article, Clayton Morrison talks us through the importance of yeast in the brewing process and some of the terminology brewers use when talking about yeast.

“Many brewers often underestimate the importance of pitching the correct quantity of healthy yeast. Yeast contains the magical little microbes that turn our wort into beer. It’s often said that brewers make wort, yeast makes beer – so very true.

As with the other three main ingredients of beer (water, malt and hops) yeast itself is equally as important. A good quality, well treated and sufficient amount of yeast should be pitched into every beer to ensure you have optimal fermentation and flavour development.

Some terms used in relation to yeast are:

Cell Count – This is the amount of yeast cells per billion (ie – a count of 150 – 150 billion)

yeast under a microscope
Yeast under a microscope

Viability – This is the effectiveness of the remaining live yeast cells. Yeast cells die from the moment they are propagated, thus rendering the yeast packet less effective over time.

Starter – A pre calculated amount of fermentable wort (either from extract or all grain) provided for yeast to ‘begin’ with (ie – a hospitable environment with a small amount of fermentables in which a quantity of yeast will consume in order to multiply and/or ‘activate/come to life’).

Building a yeast starter
Yeast on a stir plate

Stir plate – A device used in conjuction with a stir bar and flask to constantly agitate the yeast starter, and keep yeast in suspension whilst promoting gas exchange.

There are some beers (hefeweizen etc) that can benefit from ‘under pitching’, thereby not providing quite enough yeast cells to ferment the batch ‘efficiently’, that puts the yeast under stress and promotes formation of esters in the beer, which can be beneficial to the style.

However, far and beyond these few exceptions, a good quantity of yeast is important in almost all beer styles – it’s especially important in cooler fermentations such as pilsners and other lagers.

There are two ways in which you can increase the quantity of yeast you need.

1 – Purchase and pitch more yeast. Dry or liquid, using more packets of yeast will immediately up your cell count thereby providing your yeast with more team mates in which to tackle the task of making delicious beer.

2 – Use a yeast starter. Using a yeast starter gives your small amount of yeast a chance to fire up and multiply thereby as above, providing your yeast with more team mates in which to tackle the task of making delicious beer.

To explain a yeast starter in a bit more detail, we essentially need to understand what a yeast starter is.

It can be as simple as a sanitised bottle in which you contain some fermentable wort and yeast, to kick off fermentation, up to as complicated as a stir plate, flask and stir bar (which in essence, is NOT complicated at all).


Clayton Morrison,
Fermental Brewing/Grainfather Agent”

Let us know your thoughts in the comments below, what do you normally do with your yeast?

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