Low Attenuation from Late Malt Addition?

[sjfischr]

Alrighty, guys, this is the second time in succession this has happened with the same recipe. I'm making an imperial IPA which has been getting stuck at about 1.030, from a 1.102 OG wort. There have been a number of threads on stuck fermentations, but this question I have is more specific.

I'm a pretty experienced brewer. I've brewed extract since 2001, went to AG about 18 months ago, had some success with that. and went back to some partial mash/extract recipes since my daughter was born so I can save time and better ensure recipe success.

The grain bill for the recipe has been a simple imperial IPA I've brewed for the past year:
2 lbs Munich Malt (Steep)
2 lbs Flaked Rye (Steep)
12.5 lbs Extra Light DME (added late at 15 min remaining)

Instead of a starter, I've used 22g (two packets) of US-05 (Chico), brand new from LHBS--about 12% more than I need to reach optimal cell count.

Wort aeration has been simple carboy shaking for about 30s.

My guess is that the addition of the DME later in the process--a technique which IMHO largely prevents boilovers--has been causing the substantial drop in attenuation from an expected 75% to about 58%. In other words, I'm wondering if the addition of so many solids so late in the boil is somehow eliminating the oxygen which has built up in the wort for the preceding 45 minutes. While the beer is still about 10% ABV, it retains a sticky mouthfeel which is just a bit too much for many drinkers. If I can get even ten more points, I'd be happy.

Alternatives I've considered:

• Replace the late malt addition with the traditional addition at the beginning of the boil
• Boil the DME longer following a late addition
• Procure an oxygen tank and aerate that way

Please let me know what else I should be considering. I do really like this late malt addition for its added convenience, but am willing to substitute the step if it's the culprit.

THanks!

 

[brew_ny]

I do not think it is the late addition of your malt extract, sugar is sugar but maybe

do you rehydrate your yeast? if not I would

adding O2 would more then likely help

all the best

S_M

 

[Yooper]

Even with AG brewing, I normally use some simple sugar in the boil to lighten the body and to get a lower FG. That much malt and such a high OG is probably the cause. You could try your theory that the DME added late is the cause, but I think that adding it all at the beginning would increase maillard reactions and instead make the DME even less fermentable.

Some DME brands are about 70% fermentable in the best cases, and a high OG of 100% malt would definitely increase the likelihood that attenuation would suffer.

 

[sjfischr]

Hey guys,

Thanks for the quick replies. This could very well be just that the yeast is stressed getting to the attenuation it needs. Could I benefit from another strain next time, a higher cell count, or more oxygen? If you had to pick two of the three, which would you pick?