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Saturday, May 25, 2013

Home brewing - Yeast

Switching gears for a moment from historical steam turbines...

Yeast are interesting micro-organisms.  They are actually very simple single-cell fungi.  They are pretty cool organisms, because they metabolize sugars and excrete grain alcohol as a waste product.  They also generate carbon dioxide gas, which is released during the fermentation process. 

This gas is also what causes bread to rise and have the spongy texture it has.  Yeast is mixed with the dough, and allowed to eat some of the sugars in the flour.  The bread rises because yeast release bubbles of carbon dioxide gas, which is trapped in pockets in the dough.  This process of converting a flat bread into risen bread is called "Leavening".  Yeast are believed to be one of the earliest domesticated organisms, because 4000 year old bakeries have been unearthed in Egypt that have facilities for baking leavened bread.

In an environment with the proper temperature and nutrients, each generation of yeast eats, multiplies many times, and dies.  This process of eat, multiply, and death continues until they either run out of sugar in their environment, or the concentration of their own waste products finally kills them. 

In this respect yeast aren't a whole lot different than people.  Humans have multiplied to reach 7 Billion people on this little planet.  We have radioactive water seeping into the Pacific Ocean and entering the food chain.  We also have a million chemical pollutants, some of which we breathe, and others that our food comes packaged in.

But that's just a philosophical thought for the moment. 

What's important is the new batch of Orange Blossom Amber.  In addition to using the Pre-made Amber kit, this batch has one and a half pounds of orange grove honey added shortly before the end of the boil.  Didn't want the orange flavors to boil off over the course of a one hour boil, so I added it right at the end, just long enough to sterilize any germs.

Here is the Amber right after I added the yeast and installed the airlock.  The light foam on the surface is just from pouring it into the fermenter.

Here is a picture taken the following day.  The yeast are busy!  The carbon dioxide gas they release in the sugar mixture creates tiny bubbles and produces a thick foam.

Below is a photo taken on day four.  The simple sugars have been eaten and the yeast are moving onto the more complex sugars.  The airlock is not bubbling quite so fast now.  The foam has some crusty-looking brown stuff in it, which is dead yeast cells from previous generations.

Next up after the Orange Blossom Amber is a the Gold Dust IPA (India Pale Ale), a light, bitter and hoppy beer.

I also kegged a Belgian Honey Wheat beer that I made back in February.  The recipe calls for it to sit in a secondary fermenter for 4 months!  One thing I noticed is how little haze the beer has when you allow it to settle for so long.  Take a look at the fermenter and the glass.  This definitely has more clarity than any of my other brews!

This beer had a ton of fermentable sugar in it (the kit was quite expensive), and the high alcohol content actually gives the beer a little heat, like wine.  I guess it's about 10-11% alcohol or 20 proof.  I've never had a beer that burned before...

Lastly there is a cool time-lapse video I found on the internet.  It shows a week of fermentation in a couple of minutes.  When the yeast are active, they generate quite a bit of heat and cause quite a bit of circulation.  You can see the process in the fermenter, it just seems REALLY fast in time-lapse. 

So the yeast are really busy but don't accomplish much, except to quickly run themselves out of food and kill themselves in their own waste.  I'm sure there's something I could say about humanity, but I won't.  I will say this - homebrew is really cool and tastes awesome!

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