Without yeast there is no beer, so what is this tiny organism that gives us our thirst-quenching brews? And which one is the best to use?
What is Yeast?
Yeast is a single-celled organism that is responsible for turning your wort into something significantly more delicious, alcoholic and all the more pleasing. Without getting too science-y, the yeast essentially eats the sugars present in the wort - converting it into ethanol, carbon dioxide and flavour aroma compounds. Through this process it influences and creates flavour, alcohol content and carbonation.
Different types of yeast are called "strains" and each strain will impart slightly different characteristics to your brew. In the old days when beer was first produced, the presence of yeast wasn’t understood and the production of beer primarily used wild yeast, using what was available, with no repeatable results! Nowadays, specific strains and purities are used to give the exact results a brewer is after.
Yeasts can be broadly grouped into two families, ale and lager.
- Ale yeasts are top-fermenting and prefer warmer temperatures. The yeast typically used for ales is Saccharomyces Cerevisiae, which produces more fruity, spicy and earthy flavours and your beer is ready to drink sooner.
- Lager yeasts are bottom-fermenting hybrids of Saccharomyces Cerevisiae - a yeast called Saccharomyces Pastorianus. Lager yeasts prefer a slightly cooler environment and produce less esters which promote a cleaner malt and hop flavour profile. They’re best when they’ve had a couple of weeks to age and have a good crisp finish.