Ale Yeast

I felt like I’d pulled-off a feat of alchemy.

Begley

Boil some grain in a large cauldron, add some leaves, finish with some pixie dust and let it sit in a basement for a month and you end up with a delicious golden elixir.

The tactile experience alone of steeping the grains, stirring the pot and quaffing the hops was magical to say the least; never-mind the delicious product of my labors.

Magical as it may seem, the art of brewing owes it’s very existence to science. Microbiology to be exact. Today I’ll discuss just one of the major ingredients to making beer, but often the most overlooked: Yeast.

Long before Louis Pasteur identified yeast as a microscopic living organism integral to the brewing process, the German Beer Purity Laws known as Reinheitsgebot limited beer ingredients to water, barley and hops. Until Pasteur came along, fermentation of beer was either spontaneously started from the presence of wild yeasts in the environment, or from adding some sediment from a previous batch to get the process going… but no one had a clue that yeast was the “pixie dust” that got things going.

Even though the Reinheitsgebot was implemented almost 300 years before people even knew what yeast was, our use of yeast for beverage creation pre-dates even the Reinheitsgebot by something like 5000 years.

Egyptian Model of Beer Making in Ancient Egypt. Photo By E. Michael Smith.

A vessel discovered in what was once ancient Mesopotamia yielded a beer residue from 3100 BC. Beer is almost as old as humanity itself. In fact, some would argue that beer and human civilization are inextricably linked by our cultivation of grains and the understanding of complex processes to produce goods. Regardless, as magical as the process of making beer seemed to me, so too must the process have seemed magical in ancient Mesopotamia.

But it’s not magic; It’s microbiology. Most of us know that yeast are microscopic organisms that (just like when making bread) convert sugars into other compounds, the most useful of which are carbon dioxide and alcohol. Carbon dioxide is what causes dough to rise in bread making, and alcohol is what makes beer… well… beer. The other compounds and esters that are byproducts of the yeast metabolism lend flavors to the product, so yeast selection is very important to the brewing process. Therein lies the art of yeast selection in brewing.

There are typically two main types of brewing yeast: Ale yeast and Lager yeast. Generally speaking ale yeast brews at warmer temperatures and produces byproducts called esters, which can aid in adding the flowery aromas of apple, pear, pineapple, grass, hay or plums. Lager yeast brews best at lower temperatures and produces lower amounts of aromatics which better allow the flavor of the hops and malt to come through. In addition to esters, depending upon the variety, yeasts also can produce phenols which impart a spicy or clove flavor, or diacetyls which can create a woody or earthy flavor.

In the early days of Reinheitsgebot when spontaneous fermentation was the way to go, each region, or even town, could potentially have different strains of wild yeast present naturally that would lend to the different flavors of the beer. At that time, what your beer tasted like depended a lot on the luck of whatever yeast happened to be floating by on the wind.

Though the brewers in those days were not even aware of the yeast factor, brewers of today certainly are and take full advantage of that knowledge. Even the budget home-brewer can hand pick whatever yeast and associated flavor characteristics for their beer that they like. Dry yeast packets, liquid yeast vials and liquid yeasts with “activators” are all available for between $2-$10 a piece on the Internet. I get mine from Midwest Supplies in Minneapolis. Friar Tuck’s in Springfield, Ill., also has brewing supplies on hand.

But if you’re a real do-it-yourself guy or gal, then check out my quick guide on restarting yeast from your favorite off-the-shelf bottle conditioned brew! This can be especially useful when attempting to clone a particular beer flavor. You can view those instructions here: (Yeast Feast: An Easy Guide to Restarting Brewers Yeast From The Bottle)
Happy Brewing!