stuck fermentation question

hi all,

after more than 40 successful all grain brews using my 3 tier system, i'm having some problems with my last couple of brews.

my regular process has been to mash for 60 minutes, drain, sparge, drain. it has taken me usually 2 hours.

but i just recently switched to BIAB, to speed up my process.

anyway. my last two beers, a dry stout and blonde ale, are stuck at 40% fermentation. both were pitched with plenty of yeast, slurry of 1084 for the stout, and 1007 for the blonde ale. both yeasts have been 75% performers for me in the past.

i have stirred up the yeast, shaken the living daylight out of it but no luck. the temperature was 20°C and my regular water treatment which gives plenty of nutrition to the yeast.

my number one suspect is the mash time. i just mashed for 60 minutes and my new boil kettle is so powerfull that it only takes me 5 minutes to go to mashout and another 15 to start boil. my fear (and hope) is that full starch conversion did not take place.

so i have 2x30 liters of beer with 40% fermentation which i would hate to throw away.

my plan was to add 10-15% sugar to each fermenter and try to come up with a 4% beer which would be on the sweet note. do u guys think it would make sense?

another idea. if i would pull 10 liters of each and put some 20 liters in a glass carboy and add lambic culture to it. would the lambic eat the starch or would that be hopeless?

Hmm...that's tough. 40% into an attenuation is really early, which makes me suspect (like you) that it's a conversion problem. Can you grab a bottle of iodine to do some starch tests? I'd be surprised that simply switching to BIAB is killing your efficiency so dramatically, unless you've got a really course grind and the extra time sparging was helping before. That said, I can't really see what else it would be.

As for the sugar, seems reasonable enough. If you do have unconverted starch, though, it will only go so far to help. The lambic bugs won't eat the starch, but they can help to make an otherwise underdeveloped beer a bit more complex. Good luck

Just a thought on how to save it...put it in a secondary, brew up a high gravity/big beer and then mix the 2 when the big beer is done? Not very economical and you won't be able to replicate it but it's just a thought.

thanks for the replies guys.

i performed an iodine test, but i have to admit, that i've never done it before so i'm not quite sure about the result.



but i took one liter of the blonde ale used it to boil 1kg of sugar which i put back into the fermenter. 6 hours later it was fermenting all over the place.