Monday, November 14, 2011

Post Yeast Roundup


*ahem* Excuse me. It's been a long weekend of moving out the mother in law and taking care of things around the house. Not having the exam anymore is a blessing and a curse. Now instead of exercising my brain untill it's a pile of Gak, I'm exercising my body, laboring and doing stuff around the house that's gone to hell while I was studying.

Lets recap. Last week I talked about fermentation times. I've picked up some contradicting information in my few years of brewing and I decided to compare the few. The three opinions were "7 day fermentation," "7+ day fermentation," and "4 day fermentation." Check out the post last week before you read on, if you haven't already. But you guys are good readers. So I know you have. Right?

Here's my take. There's three (ish) very not distinct phases of yeast fermentation. Aerobic (with oxygen), Anaerobic (without oxygen), and the stationary phase. In the beginning we deal with all aerobic activities (not jogging). Yeast is taking in oxygen, minerals, and nitrogen in this phase to build up proteins to create healty little yeasties to get ready to send off to their first day at the booze plant.

I bestow this knowledge to you. Beware. I know chemists.
The anaerobic phase is when the yeast really starts kicking some tail. This is when the most important magic happens and alcohol is created. The yeast breaks down sugars, starting with the simplest, and finishing with the most complex. But like you or I, when the yeast do all this heavy lifting, there's byproducts. For us, it's sweat, poo, etc. For yeast it's chemical compounds like diacetyl, acetaldehyde, and hydrogen sulfide. All byproducts that give the beer a funky flavor. ALSO like us, given time, yeast will...

Clean up after themselves! Yes, unlike your gross college roomate, given time, yeast will clean up after themselves. They will reabsorb the above mentioned diacetyl and acetaldehyde. Given time the yeast will start to flocculate (fall out of suspension). Conditioning the beer all along.

If you couldn't tell already from the article, I am for the method of thinking that letting your beer sit on the yeast for a while is a good thing. 4 days is too fast, probably even 7 is too fast. The yeast need time to call out the laborers and dispatch the janitorial staff. Once your yeast is done bubbling like crazy, give it a few more days. Let it condition. This is another case for secondary fermentation, something which I'm a firm believer in. Sorry, BYO, but I'm going to have to disagree with your article.

Also thank you to the authors of Brew Chem 101, and Yeast. Both books I have read and honed my knowledge of fermentation with. You can find both books talked about right here at A Tale Of Two Brewers.

What do you think? Is 10 days way too long? Argue with me. I dare you. I know chemists.

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