Author Topic: aeration, nutrients and apparent attenuation  (Read 600 times)

Offline dilluh98

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aeration, nutrients and apparent attenuation
« on: May 26, 2016, 01:32:58 PM »
The last two of my brews have had FGs that are about 5 points higher than what I normally see with these types of recipes and yeast strains. The two things that I accidentally cut out of both of those brews was to add yeast nutrient to the boil and I didn't use my mix-stir for aeration before pitching a starter. Would that be enough to account for those 5 points?

Both brews were sub 1.050 OGs and the yeasts were 007 and 1450 (both with SNS starters). I think both beers will be plenty drinkable but I don't understand why a healthy starter pitched into a low OG wort attenuated so poorly. The 1450 pack was pretty old but the starter seemed healthy as could be and the 007 was a pretty new batch of pure pitch which I made a starter for anyway. There isn't much splashing when I transfer from kettle to carboy so is it possible that it's an oxygen thing? I thought a healthy starter would negate that. 

Any thoughts?

RPIScotty

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Re: aeration, nutrients and apparent attenuation
« Reply #1 on: May 26, 2016, 01:40:06 PM »
How was your manipulation of fermentation temperature. Are you ramping up at the end to promote full attenuation?


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Offline dilluh98

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Re: aeration, nutrients and apparent attenuation
« Reply #2 on: May 26, 2016, 01:46:06 PM »
Yup. Pretty standard: mid 60s for about a week and then raise it to the low 70s for about another week.

RPIScotty

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Re: aeration, nutrients and apparent attenuation
« Reply #3 on: May 26, 2016, 01:54:12 PM »
Yup. Pretty standard: mid 60s for about a week and then raise it to the low 70s for about another week.

Has anything about your mashing changed?

Offline pete b

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Re: aeration, nutrients and apparent attenuation
« Reply #4 on: May 26, 2016, 02:19:06 PM »
If it were me I would go back to the mix stir. I don't feel I can get that level of oxygenation by hand and I noticed a difference when I went to a mix stir in the heartiness of the fermentation the first few days after pitching when most attenuation occurs with most strains.
Are these new recipes to you with more or different specialty grains than you are used to? The only downside to using the local malster that I get most of my malts from is that its been a challenge to predict OG and attenuation because I have to plug a "close enough" malt type in when I use software.
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Offline goschman

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Re: aeration, nutrients and apparent attenuation
« Reply #5 on: May 26, 2016, 02:26:38 PM »
I have had similar problems with recent batches. My first stop, is to calibrate my thermometer since nothing in my process has changed other than adding yeast nutrient during the boil. The thermometer would likely have to be significantly off since I normally mash around 150F but I don't know what else could be the cause.
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Offline HoosierBrew

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Re: aeration, nutrients and apparent attenuation
« Reply #6 on: May 26, 2016, 02:33:12 PM »
Yeah, with a mix stir and nutrients on every batch I get consistently good attenuation. If anything I tweak recipes to finish a couple points higher on occasion. I'd bet it's a combination of the lack of mix stir, nutrients, and maybe subpar yeast performance on those beers (especially on the older 1450 pack).
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Offline kramerog

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Re: aeration, nutrients and apparent attenuation
« Reply #7 on: May 26, 2016, 02:34:27 PM »
I doubt that lack of nutrients are an issue in a low gravity fermentation.  That leaves mashing and oxygenation as the primary suspects.  If your yeast have built enough sterol reserves in the starter then I think you could forego aerating the wort but I doubt that a stir plate would do that because stir plates are about removing carbon dioxide, not so much about aeration.

Dry yeast is supposed to be made under aerobic conditions.  So one time, I pitched dry yeast into a non-aerated wort (except for incidental splashing) and got an unusually long lag.  I don't recall any negative effects to the lag.  I have since then gone back to aerating wort as my standard practice.

Offline dilluh98

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Re: aeration, nutrients and apparent attenuation
« Reply #8 on: May 26, 2016, 03:17:19 PM »
Yup. Pretty standard: mid 60s for about a week and then raise it to the low 70s for about another week.

Has anything about your mashing changed?

One batch was mashed at 152 and the other at 165 (this was for Denny's American Mild which specifically calls for that high of a mash temp - I hit my OG spot on at that temp, FWIW).

Offline dilluh98

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Re: aeration, nutrients and apparent attenuation
« Reply #9 on: May 26, 2016, 03:29:29 PM »
Thanks for all the feedback. I'll definitely be going back to aerating every batch with the mix stir to see if that shores things up. I just need to remember to do it. 😀

Offline brewinhard

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Re: aeration, nutrients and apparent attenuation
« Reply #10 on: May 26, 2016, 03:57:27 PM »
I have had similar problems with recent batches. My first stop, is to calibrate my thermometer since nothing in my process has changed other than adding yeast nutrient during the boil. The thermometer would likely have to be significantly off since I normally mash around 150F but I don't know what else could be the cause.

+1 to making sure your mash thermometer is properly calibrated. Just check it to rule this one out.

Offline denny

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Re: aeration, nutrients and apparent attenuation
« Reply #11 on: May 26, 2016, 04:10:39 PM »
I have had similar problems with recent batches. My first stop, is to calibrate my thermometer since nothing in my process has changed other than adding yeast nutrient during the boil. The thermometer would likely have to be significantly off since I normally mash around 150F but I don't know what else could be the cause.

+1 to making sure your mash thermometer is properly calibrated. Just check it to rule this one out.

Just discussed this on the latest podcast.
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Offline dilluh98

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Re: aeration, nutrients and apparent attenuation
« Reply #12 on: May 26, 2016, 04:19:07 PM »
I have had similar problems with recent batches. My first stop, is to calibrate my thermometer since nothing in my process has changed other than adding yeast nutrient during the boil. The thermometer would likely have to be significantly off since I normally mash around 150F but I don't know what else could be the cause.
+1 to making sure your mash thermometer is properly calibrated. Just check it to rule this one out.
Just discussed this on the latest podcast.
I calibrated it the week before both of these brews.