Question about Yeast Attenuation

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smokewater

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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?
 
smokewater said:
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?
Click to expand...

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:eek:
 
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.
 
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.
 
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?
 
helibrewer said:
I see the Marris Otter was a 5.5 gallon batch, how were your efficiencies comparing the two mashes?
Click to expand...

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.
 
Spintab said:
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.
Click to expand...

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.
 
BOBrob said:
More slurry/gallon in the Vienna. Volume + higher OG. Just thinking out loud.:)
Click to expand...

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.
 
Why so high a temp. on the strike water? Do you mash in a pot, and keep mash temps. using the oven? I understand the BIAB smash part; thats why I would suggest the volume + OG. Hmmm some thing in the mash temp ,possibly grain crush, but I think strike water temp. should be lower unless the temp. of your grain was real cold. Describe your mash steps in the order they are taken. Cheers:)
 

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