Saturday, November 8, 2014

The Dark Yeast Rises

If the title is off-putting, hang with me for a second. It's all very biological. No, wait, come back!

In beer, alcohol is the whole point of the study. It's the one thing you generally have to have. Of course, it has to taste good: but without fermentation, all you have is generally grainy-tasting syrup water with bitter oil in it. Kind of like a weird, brown Kool-aid that no one wants to drink. It would certainly make for some terrible parties.

So, it follows that in order to get beer right, you have to get fermentation right. That requires a minor refresher in high school biology. Enter yeast: commonly reviled, frequently misunderstood, microscopic champion of civilization. It's the hero we deserve, just not the one we need right now.

Saccharomyces cerevisiae, AKA Batyeast.
Respiration. Does that word sound familiar? Respiration is the most fundamental process in living beings for turning chemicals into energy. That's not exactly accurate, sure, but I don't have time for accurate. I only have time for beer.

When species in the Animal Kingdom respire, we typically take in oxygen, and through a series of chemical reactions with myriad starting materials, we derive energy, carbon dioxide, and water. Once you step into yeast's office, though, it's not quite that simple. Sure, it likes oxygen as much as the next Dark Microbe, but it can go without. It can take it.

When yeast doesn't have oxygen, it does something peculiar. Instead of producing carbon dioxide and water like everyone else, it produces carbon dioxide and ethyl alcohol. In beer making, this is always the intended effect. The malt sugars are the chemical input, and alcohol and bubbles come out. It's both simple and complex, really, and a wonder to watch. For me, at least. Yeast has no limits, it seems.


Except, it does. Yeast, as with all things, prefers sugars that are easy to digest. Beer yeasts tend to focus on maltose. Once you run out of simple sugars in the wort/beer, yeast will then turn to some more complicated chemicals and convert them as well. This is what brewers call conditioning. When the yeast starts doing this, it takes some chemicals which might produce off-flavors (rubber cement, cardboard, etc.) and neutralizes them. But it takes a bit more work, and the yeast isn't getting as much bang for its buck.

If you don't have enough yeast cells doing work, fermentation might be very slow, or it might stop entirely before it's work through all the chemical yeast fuel. And that is absolutely not what you want to happen. Remember the description of the alcohol-less beer above? However much of the wort doesn't see fermentation will taste exactly like that. And chances are good that you won't like it much. Maybe you will, I dunno. I personally think it's kind of disgusting.

We come, then, to the yeast starter. Yeast usually come from a lab in a state of hibernation, and are refrigerated until it's time to use them. They need water (if dry), food, good temperature control, and time to wake up and multiply. If it's too hot, they'll move too fast, produce a wide range of chemicals, then quit. Not ideal. If it's too cold, they won't want to work at all. Also less than ideal. The starter, being a small mixture of malt extract and water, is perfect for yeast to have time to get going before being added to your beer.

It's like a tiny lab kit that you can use later to make delicious beer. What's not to like?


With a little forethought and a little sanitation, I'm hoping that fermenting this Christmas beer will go off without a hitch. And it's a real rager right now. The timing gets me to Tuesday, Veterans' Day, to make the batch. Veterans, I salute you with a beer I'm planning to put in 22oz swing-top bombers. Good night!

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