Oh yeast!

ALTHOUGH YEAST is the smallest ingredient in brewing, it does the most work and is the real unsung hero in the beer-making process.

So it’s up to us brewers to make sure the conditions are conducive to give yeast every chance of giving the best possible ferment.

Yeast is a little single-celled organism responsible for the fermentation process. One of the least complex forms of plant life, yeast consumes simple sugars like glucose and maltose to produce carbon dioxide and alcohol.

Yeast can also take credit for the classification of beer styles.

Brewers pick a yeast according to the recipe or the style of beer they want to make.

Beer yeast is identified as either ale or lager yeast.

An ale yeast is a top-fermenting strain, working best at warm temperatures.

Lager yeast, in contrast, is a bottom-fermenting strain, performing best at cooler temperatures.

Because of the temperature differential, each yeast strain produces vastly different flavour and aroma characteristics that in turn will create different beer styles.

Yeast in combination with different fermentation processes and ingredients can also contribute fruitiness and other flavour characteristics to the beer.

Also, unfortunately for home brewers, it can also contribute to the ‘off’ flavours if introduced to the wrong environment, or in insufficient quantities, or at incorrect fermentation temperatures.

So how do we create the right environment?

A sanitary fermenter to start with, along with plenty of fermentable wort, cooled down to the right temperatures and an acceptable number of yeast cells to ferment the volume of wort you have ready.

So how much do we need for an average 23 litre batch?

Most well-known brewers now recommend 2–11 gram packs of dry yeast. So if you only have access to the yeast underneath the lid of your tin, this falls well short, as most of those packs are about 5–7 grams at best.

Store-bought specialty yeast will yield best results.

I do realise this is an added expense, but there is light at the end of the tunnel. Yeast is a living organism and it can be cultured, washed, rinsed and/ or re-used.

The simplest way is to pitch a fresh beer on an existing ‘yeast cake’. Take a sanitised cup , scoop out at least 300 ml of trub from your last brew, wash and sanitise your FV and pitch the cup into your next beer.

If you cannot brew until a couple of days, put the cup in the fridge with some sanitised cling wrap covering it.

All yeast keeps better in the fridge, whether store-bought liquid or dry, or your own culture. Brew by You at Invermay keep all their yeasts and hops refrigerated

Fermentis is probably the industry world wide leader of dry yeast.

The two most popular are US–05 for ales and 34/70 for lagers, but there are literally hundreds of dry and liquid yeasts to choose from.

Instead of having to pitch two packs, you can make a ‘starter’. Simply dissolve 100 grams of light dried malt into a litre of water in a sanitised vessel and cool down.

Then pitch your yeast into this and cover it.

Do this on the day before you brew, if possible, and the yeast will increase in volume enough for you to pitch the whole starter.

How this works is that when you first introduce your yeast into your beer it breeds sufficient numbers to consume the sugar. This is also how you culture and breed it.

I use Erlenmeyer flasks and stir plates and breed up larger quantities to have some on hand for future brews.

Good liquid yeasts cost upwards of $12, so culturing our own yeast for re-use is a big saving for us brewers.

Home brewers can also start building up their own yeast bank with different strains and cultures

There are lots of Youtube videos out there to show how to culture, rinse, wash and reuse yeasts. LittleJohns Channel has quite a few good, in-depth demonstrations.

A simple pale ale or draught extract tin with 500g LDM and 500g of dextrose fermented at 20°c with some US–05 yeast will make a great and vastly improved beer for your Christmas holidays.

Until next time – good brewing!