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Brews & Views Bulletin Board Service * Brews and Views Archive 2009 * Archive through December 01, 2009 * Attenuation < Previous Next >

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Bierview
Advanced Member
Username: Bierview

Post Number: 607
Registered: 03-2003
Posted From: 67.85.0.212
Posted on Wednesday, October 28, 2009 - 05:42 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Just racked an Imperial Stout with an OG of 1.095 FG 1.020. That gives me about an attenuation rate of 79%. I was dissapointed with that until I looked at the stats of the yeast W1728. It gives this yeast between 69-73%. Still.........could I have dropped it further?
 

Marc Rehfuss
Member
Username: Marc_rehfuss

Post Number: 134
Registered: 03-2003
Posted From: 199.133.212.53
Posted on Wednesday, October 28, 2009 - 06:18 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Depends on several factors. How big of a starter did you pitch? Did you oxygenate? What temperature did you mash at? How many grains that contribute unfermentables (e.g. crystal and/or dextrin malt) are in your grist? I find I can almost always push my yeast past what manufacturers list if I give my yeast a fermentable wort.

With that strain, I'd say you are done. That really is excellent attenuation for that strain, let alone in a impy. Good work.

(Message edited by Marc_rehfuss on October 28, 2009)
 

Denny Conn
Senior Member
Username: Denny

Post Number: 7295
Registered: 01-2001
Posted From: 75.145.77.185
Posted on Wednesday, October 28, 2009 - 06:33 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Yeast attenuation rating make a lot less difference than the fermentability of the wort.
 

Bill Pierce
Moderator
Username: Billpierce

Post Number: 10875
Registered: 01-2002
Posted From: 24.141.103.148
Posted on Wednesday, October 28, 2009 - 07:50 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Denny's correct that other factors have even more influence than the yeast strain in terms of attenuation, but I have to give the nod to Marc here. I agree that 79 percent apparent attenuation is as much as you could expect for Wyeast 1728 in an all-malt beer. The only thing you could have done would have been to substitute sugar for some of the malt.

Actually, I think you will be quite happy with your F.G. of 1.020 for an 1.095 imperial stout. Big beers like this are supposed to have body and just a little residual sweetness.