Default, Apparent, and Real Attenuation vs. Manufacturers

Brewing processes and methods. How to brew using extract, partial or all-grain. Tips and tricks.

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Default, Apparent, and Real Attenuation vs. Manufacturers

Postby devoneros » Tue Mar 01, 2011 2:13 pm

I'm reposting this topic from the online tools section since the last post was in 2006.
I've been using the online calculator to assist in recipe formulation. i usually leave the default attenuation box checked but I started noticing i couldn't hit my final gravities in my extract brews. upon checking wyeast's attenuation ratings for their yeast (in which they don't specify whether they use real or apparent attenuation) they were between 70 and 80%, never near the default, around 90-92. today i just noticed the real and apparent attenuation percentages in the final recipe's in the calculator and they're lower in the final recipe than the default which was reassuring but also added enough confusion to my use of the calculator to register on the forum and make my first post today.

i want to know which value between the default, apparent and real i should try to line up my wyeast percentage to.

as a side note, when i lowered the default attenuation below the standard 90ish%. i've been getting final gravity numbers which seemed more realistic in my extract brewing practices
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attenuation

Postby slothrob » Tue Mar 01, 2011 9:14 pm

70-80% seems a much more realistic attenuation target.

I just looked up the last extract batch I made, and the apparent attenuation was 72.5%. I don't think I've ever hit much over 75% with extract. The last all-grain beer I made was 75.5%, and I hit around 83% with recipes designed to be highly fermentable.

I don't really think that the manufacturer's yeast attenuation values can tell you much about the attenuation of your beer because recipe and fermentation conditions are overriding factors. That's just an opinion, though, I haven't tried to test it. However, White Labs lists WLP002 at 63-70% attenuation, and I've surpassed 80% attenuation with that yeast.
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Re: attenuation

Postby bobcat_brewer » Wed Mar 02, 2011 9:32 am

slothrob wrote:However, White Labs lists WLP002 at 63-70% attenuation, and I've surpassed 80% attenuation with that yeast.


Wow- you've got to tell me how you created that wort! I've never attenuated like that with that yeast. What were you making?
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WLP002

Postby slothrob » Wed Mar 02, 2011 9:44 pm

I get closer to 71-75% attenuation with WLP002 on a lot of beers, but I brew a dry Pale Ale with my homegrown hops each year that attenuates from 77.5 - 81% (looking back into my BeerTools Pro archives). It's just Thomas Fawcett Maris Otter, 1/4# Crystal Malt (CaraStan or CaraMunich, usually) and sometimes a little Aromatic Malt, mashed at 150F, followed by a lot of late hops.

Looking back at the recipes, I was surprised to see that mash temperature. I thought the mash temperature would have had to be lower to get that level of attenuation.
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Re: WLP002

Postby bobcat_brewer » Fri Mar 04, 2011 9:23 am

slothrob wrote:Looking back at the recipes, I was surprised to see that mash temperature. I thought the mash temperature would have had to be lower to get that level of attenuation.


I agree. I thought you were going to come back and say you mashed at about 145! Kudos, you must really be paying attention to your fermentation. Are you actively raising the temperature as the fermentation proceeds?
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Re: WLP002

Postby slothrob » Fri Mar 04, 2011 9:16 pm

bobcat_brewer wrote:I agree. I thought you were going to come back and say you mashed at about 145! Kudos, you must really be paying attention to your fermentation. Are you actively raising the temperature as the fermentation proceeds?

I do sometimes mash at 145-148°F for some beers, like Alts, which I also ferment cool, raising the temperature toward the end of fermentation.

That Pale Ale is always fermented at 62-64°F, however. I do pitch a generous amount of yeast when using WLP002, though. Usually I repitch about 1/4 of a fresh yeast cake. A lot of people use WLP002 in beer recipes that contain a lot of Crystal Malt, too, which I actively avoid with that yeast.
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