Yeast is, fundamentally, the most magical part of the beer-making process. Once wort (unfermented beer) is made in the brewhouse out of raw materials – malt, hops, and water – we’re left with a thick, flat, bitter, and sweet liquid that, if left in that state, no one would ever want to drink. Frankly, it’s gross.
But that’s where the magic of yeast comes in!
Yeast takes those sweet sugars and, through fermentation, metabolizes them into energy to produce more yeast and releases CO2 and ethyl alcohol as waste. The CO2 is vented off into the atmosphere, but that wonderful alcohol byproduct left in the fermented beer may be what started human civilization as we know it.
Now, there are two primary types of brewing yeast: Ale and Lager, and the differences seem simple at first: Ale ferments at higher temperatures (60°-80°F) and is characterised by fruity to funky flavors and aromas from its esters; while Lager ferments at lower temperatures (35°-55°F) and is characterized by clean, crisp, and almost non-existent yeast flavors and aromas.
Lagers are much more of a process than their ale counterparts. Once the wort and the yeast is pitched, fermentation begins shortly thereafter. In our brewery, Ales take off with a roar and ferment a batch within 7-10 days, often spewing krausen out the tank in the process. It’s a dramatic, fruity-smelling, and foamy party for the yeast until they exhaust themselves and their resources and eventually fall to the bottom of the tank. If you think of it as a massive orgy of single cell organisms partying by cloning themselves until they can’t anymore, you’re really not that far off. 2 weeks after fermentation is over, the beer is clear, carbonated, and in your glass ready to be drank.
Yea, I said, “Orgy…”
For lagers, fermentation takes off with a whimper and concludes two to three weeks later with an even slower, much stinkier whimper. During that time, the smells emanating from the CO2 venting from the tank can be fairly described as ‘gross’ and ‘farty’ to ‘sulphurous’ and ‘intensely terrible’. For a brewer, it tests not only your patience, but your entire confidence in whether you actually know what you are doing or not. The beer fermenting away in the tank goes through different phases that produce off-flavors like the slick, buttered popcorn flavor of diacetyl and the sulphurous grossness of DMS that you normally avoid at all costs as a brewer. You taste them as you check on the tank daily and almost freak out, but then you say to yourself, “Brewers have been using this yeast for 500 years to fantastic results. Stay calm.”
Once the lager yeast finishes its primary fermentation, it then needs an additional 4-6 weeks of conditioning known as lagering. During this time, much of the yeast is still in suspension in the beer as it begins cleaning up those off-flavors that it created in the first place. Slowly but surely the diacetyl goes away. Then the DMS goes away. Then other, more subtle bad stuff from the yeast’s unique esters and phenols that you didn’t even notice at first goes away. The further time goes on, the beer begins to be clearer and cleaner as your confidence as being a legitimate brewer grows by the day.
Then, some 2 months after entering the brewhouse as raw ingredients, it’s clear, carbonated, and ready for you to take a sip out of your glass. And the results are remarkable: beer that is clean and crisp, with as little to no flavor from the yeast imaginable. With styles like Marzens (which Creston Lager can be characterized as a hopped-up version of) and Pilsners (that Creston Pilz is a totally Michigan-ian take on the classic style), you taste the fermented results of your raw materials and almost nothing else. The hops come through as clean, bitter, and aromatic as the day you made the wort, while the malt takes on fascinatingly bready, toasty, grassy, and subtle flavors that were buried in their malted sweetness
previously. And oh, that great Lake Michigan water that we use makes everything taste just so smooth, that you just can’t help but put it in bold, and underlined italics to emphasize its importance to the whole shebang.
So here’s a cheers to those early lager brewers that didn’t give up on their stinky ‘mistakes’, because they changed the beer game forever!
Long live lager! (and ales too!)