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Old 12-19-2011, 03:42 PM   #1
smokewater
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Default Question about Yeast Attenuation

I did 2 BIAB SMASH brews one week apart. The first was a 5.5 gallon Marris Otter/Ammarillo brew OG 1.062. The second was a 4 gallon Vienna/Amarrillo OG 1.059. The MO batch sat on the primary 3 weeks. The Vienna batch sat 2 weeks. Both batches used the same yeast slurry.

I washed the yeast by dumping about 2 quarts of boiled/cooled water onto an S-05 cake, swirled it around, filled 2 quart mason jars with slurry and placed that in the fridge for a couple of weeks. I used about 3/4 of the jar in each batch after decanting the clear liquid. Both batches started showing air lock activity within 24 hours. I made no starter with either batch.

I bottled both batches yesterday

The Marris Otter batch reached a FG of 1.020 after 3 weeks from OG1.062

The Vienna Batch reached a FG of 1.012 after 2 weeks from OG1.059

Both were mashed around 152 for 1 hour. Why the lower attenuation in the Vienna batch?

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Old 12-19-2011, 03:46 PM   #2
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Quote:
Originally Posted by smokewater View Post
I did 2 BIAB SMASH brews one week apart. The first was a 5.5 gallon Marris Otter/Ammarillo brew OG 1.062. The second was a 4 gallon Vienna/Amarrillo OG 1.059. The MO batch sat on the primary 3 weeks. The Vienna batch sat 2 weeks. Both batches used the same yeast slurry.

I washed the yeast by dumping about 2 quarts of boiled/cooled water onto an S-05 cake, swirled it around, filled 2 quart mason jars with slurry and placed that in the fridge for a couple of weeks. I used about 3/4 of the jar in each batch after decanting the clear liquid. Both batches started showing air lock activity within 24 hours. I made no starter with either batch.

I bottled both batches yesterday

The Marris Otter batch reached a FG of 1.020 after 3 weeks from OG1.062

The Vienna Batch reached a FG of 1.012 after 2 weeks from OG1.059

Both were mashed around 152 for 1 hour. Why the lower attenuation in the Vienna batch?
Could you describe the "SMASH" part? I'm just curious for trying this later. I mean do you push on them with something? I've seen people just stirring the bag.

edit: LOL, I just looked it up and feel dumber
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Old 12-19-2011, 03:49 PM   #3
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SMASH means Single Malt And Single Hop. Its a good way to learn about various flavor characteristics of malt and hops. Makes pretty good beer too.

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Old 12-19-2011, 04:21 PM   #4
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I'm no chemist but I'd say the reason is in the characteristics of the two different malts. Each will give you a slightly different mix of beta and alpha amylase at the same rest temp. One may also affect your mash PH a little different from the other.

I guess the question I have is given an identical OG from mashes rested at two different temperatures, will attenuation be the same? I know this isn't the situation here but it may be an interesting piece int he overall puzzle.

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Old 12-19-2011, 04:34 PM   #5
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So the Vienna batch was spot on, .25X59=11.8

You might research the Marris Otter to see what it's mashing characteristics are, in theory it should have finished around 15. It might give you a brew with a bit more body that you really like

I see the Marris Otter was a 5.5 gallon batch, how were your efficiencies comparing the two mashes?

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Old 12-19-2011, 05:22 PM   #6
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Quote:
Originally Posted by helibrewer View Post

I see the Marris Otter was a 5.5 gallon batch, how were your efficiencies comparing the two mashes?
Using Beer Calculus:

Beer Calculus . homebrew recipe calculator

Beer Calculus predicted the Marris Otter batch at a FG of 1.017 from a starting gravity of 1.061. set at 75% efficiency.

Beer Calculus predicted the Vienna batch predicted at a FG of 1.016 from a starting gravity of 1.058 set at 75% efficiency.

I was a little higher on both of those OG's post boil.

Looking at my log I pitched the MO batch at 77F and the Vienna batch at 69F. Both times the bucket was sitting in a water bath with ice around around it and the temp was in the low 60's within a couple of hours. My fermentation room is about 65F and i keep a couple of ice packs in the cooler the first couple of days after active airlock activity starts.

I probably pitched a little more slurry/gallon of wort in the Vienna batch than the MO.
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Old 12-19-2011, 05:29 PM   #7
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Quote:
Originally Posted by Spintab View Post
I guess the question I have is given an identical OG from mashes rested at two different temperatures, will attenuation be the same? I know this isn't the situation here but it may be an interesting piece int he overall puzzle.
That is an interesting question. This was no where close to a scientific study. There were too many variables to consider. I was expecting the FG to be a little lower in the first batch though I have had several other batches finish at 1.020 using fresh S-05 dry yeast packages. This was my first attempt at using a slurry. That's why I was a little surprised the second batch came in so much lower after a week less in the primary with basically the same yeast.
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Old 12-22-2011, 09:02 PM   #8
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bump

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Old 12-22-2011, 09:39 PM   #9
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More slurry/gallon in the Vienna. Volume + higher OG. Just thinking out loud.

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Old 12-23-2011, 12:27 AM   #10
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More slurry/gallon in the Vienna. Volume + higher OG. Just thinking out loud.
That's sort of what I was thinking initially. I was considering not bottling the Vienna batch at 2 weeks when I pulled the MO gravity after 3 weeks.

I did a 2 step process sparging in another pot at 170F with an additional 2-3 gallons of water to reach my boil volume for the larger MO batch.

The Vienna batch was smaller and I did a mash out step at 170F with no additional water added. It fit in my 8 gallon boil kettle.

Perhaps the strike water temp (around 195F) produced some unfermentable sugars initially before before equalizing at 170 in the second pot. For the Vienna batch I used the burner to raise the temp with no second pot.
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