Yeast – Making Beer Work
When posting this article I have categorised it as an ingredient. It is I suppose but as well as that it is a process. Without yeast there is no beer. No alcohol at all.
Ok so here it is the thing that turns sweet malty wort into infinitely differing flavours and types of beer. First of yeast is a living organism. It is a fungus and that is why you have infinite varieties. So many in fact that every brewery will have their own strain of yeast that is usually a closely guarded secret. Like all living organisms it adapts to conditions that is why some yeast perform differently in beer than others. English Ale yeasts for example are top fermenting, lager yeasts are bottom fermenting and favour cooler temperatures.
To the homebrewer. You will have two options available when buying yeast to make your own beer. This will be liquid yeast or dried yeast. I have used both successfully and they both produce first class beer but I favour liquid yeast because of the sheer variety. Take a look here “White Labs” and you will see.
Dried yeast on the other hand have less variety and are chosen because they are suitable for dehydration more than other strains. That’s not to say they are not good to use because they are certainly easy to store as they are happy to just sit in the packet whereas liquid yeast will need to be refrigerated and will lose viability much sooner.
The wort produced from mashing grains and boiling the wort with hops contains all the nutrients that the yeast need to begin making beer. The main nutrient needed is sugar and the yeast consume this sugar and the byproduct is carbon dioxide and ethanol or alcohol. Along the way all sorts of other byproducts are made by the yeast that effect flavour and aroma of the finished beer. Another thing that effect the yeast activity is the temperature the higher the temperature the more flavour chemicals such as esters and fusils are created. This is why there is such a profound difference between Lager and Ale for example.
One important thing to remember before adding any yeast to wort is, the wort needs to be aerated either by splashing, shaking or pouring as without oxygen the yeast won’t reproduce from the amount in the packet or vial to the volume needed for your batch.
When choosing a yeast there will be several factors that effect your decision as listed below.
Attenuation – The percentage of sugars the yeast consume in fermention
Flocculation – This is the degree to which the yeast cells will group together at the end of fermentation. In some beers like English Ale this is highly floculant and provides a clear beer in Hefeweizen is low flocculation and is cloudier
Optimum Fermentation Temperature – The temperature at which the yeast is happiest to ferment.
Alcohol Tolerance – As alcohol increases the fermentation slows as yeast have a certain tolerance at which they will not continue fermenting without further nutrients.
I will post further topics on these factors but this is more than enough for now.