unfermentable porter

Brewing Processes
1

So I brewed a harvest porter recently with baked sweet potatoes, acorn squash, and sweet nugget squash in the mash. I originally undershot my mash temp and added the baked ingredients almost directly out of the oven. I noticed the mash temp rise to my intended temp in a few minutes however I foolishly didn’t pay attention as the mash progressed.

All fermentation activity seemed normal but it has stopped in the mid 1.020s. The OG was around 1.054 from what I remember. My fear is that the mash temp rose above 158 which has severely limited attenuation. I roused the yeast and warmed the beer without any effect. I decided to pitch a pack of US05 yesterday without any luck either.

Any other thoughts other than too high of a mash temp? I haven’t decided if I will keg the batch or dump it yet. I am contemplating re-brewing it however that will really mess with my schedule…

2

have you performed a forced ferment test?

pull about a pint of beer and pitch a whole packet of us-05 and aerate the heck out of it. if that brings it down any you should be able to krausen the whole batch if you can get enough vigorous yeast cells in there (call the local brewery and beg a quart of slurry)

3

I have not tried that. Thanks for the idea.

4

Came home tonight to a continuous film covering the top of the beer. Must have become infected?

5

What does the film look like? Could you post a picture?

6

Depending on how much of the veggies you used, maybe there wasn’t enough diastatic power in the mash to convert everything fully?

7

Throw in a pack or two of rehydrated Belle Saison yeast.  That should improve attenuation considerably.

Too bad if it got contaminated.  You could drink it up real fast if you like, but it sounds like you don’t want to do that.  Keep your fingers crossed.  Maybe it will still turn out.  The odds do seem against it though.

8

It’s possible that it fermented as it was supposed to. You have to take into account the viability of the yeast and the overall OG. My second thought is that you might have added so much sugar from the extra ingredients, the yeast couldn’t get past 1.02. My third thought is that your grains may not have had enough time at the correct mashing temperature to convert all the starches to sugar.

Cheers