always have low attenuation, what's up? - Home Brew Forums
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Old 01-29-2013, 04:21 PM   #1
hexXedBrewing
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Jan 2012
escondido, ca
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So I've made 9 batches so far, and just had my first all grain batch. For whatever reason, I'm getting low attenuation rates like around 65% to 70%. all using 2liter starters and white labs. I've even tried super San Diego yeast and I only got 71%. I've gotten 76% twice but they were both low gravity beers. can anyone lendme some hints? my temperatures for all my beers are about 69F.



 
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Old 01-29-2013, 04:37 PM   #2
mcbethenstein
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Mar 2011
Waukesha, WI
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Tell us more about how you oxygenate and if you are using any sort of yeast nutrient.



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Old 01-29-2013, 04:48 PM   #3
rkbarnes82
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Oct 2011
Fort Bragg, NC
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What are your mash temps?

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Old 01-29-2013, 04:59 PM   #4

In addition to mash temps (as RKB82 asked above), your recipe will also affect attenuation. Crystal/caramel malts, for example, add unfermentables to the wort that the yeast won't eat up. In other words, they raise your FG, lowering your attentuation percentage.

Where is your FG ending up? What you are really interested in is hitting your target FG, not the attenuation, which is just a percentage. For example, my Belgian Golden Strong had a huge attenuation, because it started high and ended dry (as intended). My cream ale ended dry, also, as I wanted it, but the attentuation is lower because it starts lower.

To increase your attenuation or to get a drier beer on, say, a basic APA, try following these steps:

1) pitch using either rehydrated US-O5 or make a big starter of WLP001
2) use no more than 1/2 lb total of crystal or caramel malts in a five gallon batch
3) mash at 148F - 150F for 75 minutes
4) oxygenate your wort - pouring into your bucket back and forth, stirring the wort in the bucket vigorously, shaking the carboy, or adding pure O2 through a wand
5) start your fermentation at 62F-64F and when the active fermentation slows, raise it to 68F - 70F.

Hope this helps!

 
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Old 01-29-2013, 05:02 PM   #5
cfonnes
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Jun 2010
Utah
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Type of LME or DME?

How do you provide oxygen?

 
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Old 01-29-2013, 05:08 PM   #6
Xpertskir
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May 2012
Morgantown, Wv
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your post is vague and this is a complex issue.


Possible problems..

mash temp too high
too much crystal/cara malts
too little healthy yeast
too low of a fermentation temperature
not enough wort oxygenation
strain of yeast

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Old 01-29-2013, 06:27 PM   #7
cfonnes
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Jun 2010
Utah
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Opps I did not read his original post correctly.

I assumed that he was an extract brewer.

 
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Old 01-29-2013, 06:29 PM   #8
hexXedBrewing
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Jan 2012
escondido, ca
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yea I know it's vagueI'm really sorry. It's just that it's been such a long running issue.

So here's my last batch:
All grain
15lb of pale malt
1lb of crystal 60
1lb of carafa II
149F perfect mash temp for 60mins in my cooler.
did first runnings and then another test at 149F for 40 mins for my second runnings.

90 minute boil. with 15 minute wort chill to 75F.

OG came out to 1.081 at 5.0 gallons. 67% mash efficiency. =(

San deigo super yeast white labs 2 liter starter. on a slow stir plate.

I always pour the wort at 75F to my primary bucket through a sanitized strainer to catch the moss and hops, and for extra aeration.

Fermented first two days at 72F and then a total of 15 days at 68F.

I took the FG while racking to secondary and it's 1.025. I'm holding secondary at 60F for 3 days with dry hops, and then I will bring it down to 35F and hold that for 10 days.

That's pretty much all I did.

Should I really be pouring the wort back and forth, I would be afraid of contamination.

 
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Old 01-29-2013, 06:34 PM   #9
hexXedBrewing
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Jan 2012
escondido, ca
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I also used the white labs yeast nutrient at 10 min boil.

 
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Old 01-29-2013, 06:42 PM   #10

I'm not sure about the pouring back and forth, I don't do that. But for a 1.081 beer, getting enough oxygen for the yeast is an issue. Pouring through the strainer may be enough.

That's a big beer, so that will affect attenuation, too - as the fermentation continues, the environment will get more hostile for yeast (because of the alcohol) as they keep trying to do their jobs.

Lowering the fermentation temps as you go is counter-intuitive to me. As things are getting harder for the yeast, you make it even harder by chilling them. Plus, the off-flavors associated with higher fermentation temps mainly develop early in the fermentation.

The crystal 60 is going to add sugars that won't ferment. I've not used Carafa II, so don't know if that is true for it, also.

Before giving up in despair maybe try a nice, regular sized APA or brown ale, something around 1.050, keep the crystal at a minimum, reverse your temperature regime, try a US-05 (known for super attenuation and according to some doesn't require oxygenation) and see how it goes.

I can hear your frustration. Let us know how things go for you.

Edit: Have you double checked your thermometer for accuracy, that you are accurately measuring mash temps?



 
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