For how long should you rehydrate/proof yeast before pitching?

Question

I have just started brewing again after a very long break. I've tried a few brews from kits, and for my latest brew I decided to create my own wort from LME/DME and hops (pellets).

I basically followed John Palmer's Cincinnati Pale Ale recipe.

As this was my first homemade wort, I followed the instructions pretty close to the letter (even a small boil over). I boiled all the water, including 12 litres that I added to the fermenting bin at the start of the process.

The problem was that water hadn't cooled nearly enough by the time I'd crash-cooled my wort, so the final temperature of my the combined water and wort was still around 32C - too hot to pitch the rehydrated/proofed yeast (Safale US-05).

I continued to cool the wort in the ice bath, but it meant the yeast had been rehydrating for around 5 hours before I finally pitched it into a 22C wort.

Within a couple of hours (by which time it was close to 11pm), the airlock was bubbling. But the next morning, there was no activity at all.

Over the course of the next day, I noticed the krausen developing, but no pressure building in the airlock. It wasn't until ~30hours after pitching that the bubbling started again. By this time, the krausen was 8cm/3inches high, so there was definitely something going on, but this only lasted for about 12hours.

The temperature in the brewing room is fairly consistent around 17C.

My question is, is there a time limit on rehydrating the yeast? Has the extended time rehydrating caused this strange fermentation behaviour, or is it likely I've done something else wrong, or is it most likely that this beer will work out fine in the end?

Answer 1

If you have a kraüsen of 8cm thick, then your yeast is certainly in good health.

I have also hydrated yeast sometimes even 24 hrs beforehand. 5 hours is not a problem, I would surmise that the yeast is in or just behind the lag phase.

I suppose that in this case the low temperature might be the cause. You pitched at 22° C, which made the yeast active. But you put it in a relatively cool chamber, so the yeast calmed down and then adjusted to the new temperature, then began fermenting again because there were still many sugars in solution.