Revitalizing yeast cake with 1.040 wort for next big beer

[bmaupin]

I just made a 1.080 WY1762 beer and want to reuse the yeast cake for a 1.100 belgian imperial stout. Since the consensus is that yeast are pretty much spent after creating a big beer, I made a 3.5L 1.034 batch of wort and dumped it into the fermenter after racking out the previous batch last night. This morning when I checked on the fermenter (in ferm chamber at 65 degrees), it was noticeably warm inside as if the yeast were working hard, but was barely bubbling, and had a good krausen on top. This afternoon it seems to be done, indicating that it was almost done this morning. To me, the yeast seem good to go.

So my question is ... does anyone have any previous similar experience to think this won't do the job?

 

[Bowtiebrewery]

My only suggestion would be decant the 'beer' off the top. Then when its brew day, I would create a quick 1.040 starter again and let it go so when you pitch at the end of the day, you will be actively fermenting at that point. It should take off like a shot and the chances of you stressing the yeast is little to none.

 

[bmaupin]

Thanks for the reply. I think that creating a second starter is a great idea, and I think I'll dilute 1.5L of the chilled wort and add that initially and aerate, then add the remainder of the wort the next morning and aerate again.

Update: the blowoff tube started bubbling late yesterday and is still bubbling tonight. I've been swirling the fermenter every hour when I've been home. I'd say there wasn't as much viable yeast as I thought. The 2-step starter will certainly be helpful.

 

[bmaupin]

I brewed yesterday, OG 1.108. Racked off previous 3.5L starter. Diluted 1.5L wort with 1.5L boiled water and added that to yeast, oxygenated with pure O2 at 0.12L/min for 1 minute. 1" blowoff was slowly bubbling this morning. Added rest of wort and oxygenated with 2 minutes at 0.5L/min, and it's already bubbling the blowoff about a burp per second. Ferm chamber at 65. I'll update in a few weeks.

 

[bmaupin]

Yeast was more than capable as it went to 1.030 in 5 days. Would not budge from there, so I figured that mashing at 154 was not in line with a 1.022 FG - not sure what I was thinking :/. Added 1/2 tsp alpha amylase and it started slowly burping within 12 hours. After 7 days was down to 1.024, so I let it go another 3 days, cold crashed, and then racked to secondary. Hopefully start drinking in another month or so.