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Old 12-13-2007, 10:54 AM   #1
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Default Attenuation ?

My last 2 batches have failed to ferment down to the predicted FG. In fact they have been .008-.01 short. Upsetting a little I had high hopes for the most recent beer, I hit the OG dead on (first time ever).

My procedure is this. I make a 1000ml starter 2-3 days prior to brewing. I always use the instructions on the back of the Wyeast pack for doing so. I cool my wort to 72-74° before pitching. I aerate using oxygen for about 30 seconds prior to pitching. My beers usually begin aggressively fermenting 12-24 hours. They ferment at 65-70°.

I realize that 1000ml is not huge for a starter. That would however affect the lag time more than the attenuation correct? That said I would assume then I am not aerating correctly then. What do you guys do?

Cheers!!!

Follow up... Is there anything I can do with my beer in the fermenter. It has been there going on 4 weeks.



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Old 12-13-2007, 12:59 PM   #2
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If you're mashing, I'd guess that your mash is more likely the culprit and not your yeast. Mash temperature, pH, water/volume ratio, etc can all affect the fermentability of your wort.



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Old 12-13-2007, 01:53 PM   #3
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I'm having the same problems as you.

I'm going to get an O2 kit because I thought aeration was my problem, but it sounds like you are using O2 and still having issues.

I'll still do that, but maybe I need to pay more attention to my mash. I haven't been having any problems there, so I don't know what it could be.

I'm also going to do an extract kit or two. If I do not have any problems with them then I'll know its the mash.
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Old 12-13-2007, 02:08 PM   #4
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I had this same issue when I first started using my brewery... I was mashing too high (temp).

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Old 12-13-2007, 03:07 PM   #5
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Some time ago I wrote this article to answer exactly your question. Let me know if it helped or not. I may have to add some more info.

One thing to take away is the forced ferment test. This is not widely practiced in american home breweing but It can give you very valuable information about the FG that you can expect and if you don't hit it it tells you to look for the problem in the wort (mash or extract) or in the fermentation.

The attenuations given for the yeasts, and on which most FG predictions are based on, are only a very rough guideline and don't take mashing into account.

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Old 12-13-2007, 03:26 PM   #6
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Quote:
Originally Posted by Kaiser
Some time ago I wrote this article to answer exactly your question. Let me know if it helped or not. I may have to add some more info.

One thing to take away is the forced ferment test. This is not widely practiced in american home breweing but It can give you very valuable information about the FG that you can expect and if you don't hit it it tells you to look for the problem in the wort (mash or extract) or in the fermentation.

The attenuations given for the yeasts, and on which most FG predictions are based on, are only a very rough guideline and don't take mashing into account.

Kai
Kai - I read your article when you first posted it. I think its a good discussion of attenuation and I found it informative.

From the perspective of a homebrewer who has had some trouble with attenuation, I thought it would benefit from including a discussion of factors that a homebrewer can control that directly impact attenuation. For example, mash temp, fermentation temp, pitching rate, yeast choice, yeast nutrients, aeration, etc.

It would be great if each of these could be discussed separately and ranked in terms of their affect on attenuation. I'm not sure if the data exists to make a rigorous comparison, but that's OK. It would still give a homebrewer a checklist to work through when trouble shooting an attenuation problem.

I guess what I'm thinking of is something along the lines of a more general discussion of factors that ensure a good fermentation, like in Palmers book (here). That may be taking an article on attenuation too far afield.

Anyway, thanks for the article. It did help.
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Old 12-13-2007, 03:31 PM   #7
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I notice that for the most part my attenuation is higher than anticipated. My brews usually finish a bit lower than targeted. My average AT is around 80%-85%. I'm pretty sure this is due to my mini-mash temps though. I tend to err on the lower side of the temp as opposed to the higher. I guess I'm always irrationally concerned about overly sweet brews or tannin extraction.

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Old 12-13-2007, 03:37 PM   #8
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Quote:
Originally Posted by Nate
If you're mashing, I'd guess that your mash is more likely the culprit and not your yeast. Mash temperature, pH, water/volume ratio, etc can all affect the fermentability of your wort.
Thanks Guys!

First off I am at work and haven't the chance to read the links. (I will).
I was thinking that if I hit the OG that would "tell" if the mash is correct. Are you guys saying there is more to it?
Again sorry I am posting without reading the links.

Please let me know how the extract goes Beertoven I will be interested to find out.

Cheers!!!
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Old 12-13-2007, 04:34 PM   #9
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Assuming you are doing all grain the single factor you have the most control over is your mash temp. As everyones system and process differs recommended mash temps are a guide only. You will need to know your system and adjust accordingly. For instance if I mash at Jamil's "sweet spot" of 154 I end up 0.002-0.003 points higher then target so my "sweet spot" is 152 - a little lower which increases fermentability and attenuation.

GT

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Old 12-13-2007, 04:47 PM   #10
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Well it might have been the mash in my case.

2 brews ago I missed the OG .007 on the low side. (Having less sugars to convert may have been the issue).

The Last brew had an S-load of corn (20%). Palmer says many times beers with a lot of adjuncts are sometime low on minerals the yeast need.

What do you guts think???
I guess the attenuation issues might have been 2 separate problems with the same result. Regardless of all that I am going to aerate the crap out of my next batch.



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