Saturday, November 23, 2013

A split batch experiment... the impact of yeast in beer.

Do you want to see how yeast impacts the favor of beer?  Take the simplest recipe of a beer, split it into two fermenting containers and pitch a different yeast in each.  In a few weeks, you can bottle the beer and try it.  Or, if that is too much trouble then relax, I've done the work for you.

A few weeks back we talked about the Munich Malt and Spaltz hops simple recipe beer.  Read the background here and then come back.  

This was a solid 5 gallon batch, and my largest carboy is 5 gallons, which doesn't allow for much headroom.  Plus, I wanted to do something different, so I split the batch, pouring 2.5 gallons into two 3 gallon carboys.  In one carboy, a dry packet of US-05 yeast was pitched and in the other Wyeast Kolsch yeast with a 800ml starter was pitches.

In the end, there is a distinct difference in the flavor of the beer, which we can get into in a bit.  Both finished at 1.010 (with the US-05 maybe pushing more toward 1.011).  Both have about the same color at the end.

The process was interesting too, as the Wyeast carboy began fermenting, much quicker, while the dry yeast took longer to get to active fermentation.  The photos below do a nice job of illustrating this.

After pitching.  US-05 on the left, Kolsch on the Right
After about 10 hours.  Activity on the right.

Day 2, about 36 hours.

Day 3, about 60 hours, activity on the left now.  Right is beginning to settle down somewhat.

Day 7, gravity check and color comparison.
Gravity on day 7, 1.012  (This was the Kolsch.)

Kolsch FG - Day 19.

US-05 FG, Day 19
Flavor?  The US-05 American Yeast is a cleaner yeast, which gives the beer a little sharper mouthfeel, and "cleaner" taste.  The hop bitterness is right there, along with the malt background.  A nice clean simple beer.

The Kolsch yeast yielded a higher ester profile.  The beer is more round on the mouthfeel, more fruity notes come through.  At bottling time the yeast character come through, which should subside someone.  Being a low floculating yeast, there is more still in suspension.  With time in the bottle, and additional chill time, the yeast will continue to drop out, clearing up the beer more.  Even in the two photos above, you can see that the Kolsch is more cloudy.  

Note also the activity level of the yeast.  The liquid yeast with starter was much more ready to go to work than the dry pitched yeast.  There were probably more cells in the dry packet, but I didn't bother to re-hydrate them.  I bet that would have made a difference too.  It's funny, because everyone will say to re-hydrate the dry yeast.  The packet itself says to pitch directly to the wort.  Go figure.

Now the questions remains, which will taste better?  Or is there a true definition of better in this sense?  They simply are different.

With the underlying style aiming for an Altbier, the Kolsch yeast will give that character more than the US-05.  The true malt and hops character will shine more with the cleaner US-05 yeast.  Hmm.  This seems to have been a good experiment.


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