The third post in our look at the brewing ingredients takes a look at yeast. I saved yeast for last as it is the most important ingredient in the brewing process. It is said as brewers our chief job is making a happy and comfortable environment for the yeast, and that it is the yeast that does all the hard work. That's not all that far off. The process of fermentation does more than just convert sugars in to alcohols. Yeast can contribute to the flavor of the beer, it can make a beer light and dry, or heavy, or even a touch of sweetness. If the environment isn't right for the beer it can cause bad flavors, or even halt the fermentation entirely.
There are many different types of yeast. The yeast used in beer, Saccharomyces cerevisiae, isn't simply the bread yeast that you grab on the shelf of your local grocery store. It's a yeast that is well suited to tolerate continued fermentation in the presence of alcohol, and provides a range of complimentary flavors for the beer. Could you ferment with some other yeast like a cheap bread yeast? Well technically some fermentation will occur, but the yeast will likely halt the fermentation process early on, and one can only imagine the types of flavors this yeast might end up producing while metabolizing the sugars.
Speaking of metabolizing, the main function of the yeast is to consume the sugars in the wort (the proto beer, the liquid we have after extracting the sugars from our grains) and produce the by products of alcohol and CO2. That sounds pretty straight forward, but it's not quite as easy that. If the temperature is too high your yeast can start producing "off flavors", creating types of alcohol with very unpleasant tastes. If your temperatures are too cold your yeast could fall out of the beer before it's finished fermenting leaving you with very little alcohol and a sweet malty flavor. The ideal temperature can very based on the strain of Saccharomyces cerevisiae used. That's right, there's more than just one single strain of beer yeasts. There are hundreds that are employed commercially today. Each of these strains has their own ideal fermentation ranges so its important to know about your yeast.
Yeast also does more than just simple fermentation. The types of byproducts that it creates can contribute favorable flavors to your beer. Some yeasts are known as "clean" which simply means that they don't lend characteristics to the flavor of the beer; they let the malt and hops shine through completely. Some yeasts can add a slight fruit like after taste to the beer, some a peppery taste, some a big bready taste. The point is yeast is more than simply the conduit through which beer gets its alcohol. It's the biggest and most important piece of the beer puzzle even though it is the least publicized of beer ingredients.
So that's a look at the third major ingredient in beer, and wraps up nicely a little primer about how the different attributes all work together to make a tasty beverage. Come to Rogues' Harbor Inn in the heart of NY's Finger Lake regions and try our brews for yourself and see if you can pick out all the various flavors and aspects of the beer!