Dry Yeast Rehydration and O2 experiment

[Kaiser]

Thanks, Bobby.

I was surprised to see the great attenuation difference between the control and the other fermentations. Did you keep rousing the yeast in the control fermentation?

Such great difference could be the result of very locculant yeast which falls out of suspension well before the job is done.

Kai

 

[sirsloop]

all this science hurts my brain...I need another apfelwein...

 

[Bobby_M]

I didn't rouse the control at all. I suspected that the ridiculous overpitch would get it fermented out as far as it was going to go.

 

[shafferpilot]

This brings up an important point. perhaps the next experiment should be, Pitch Rate vs Attenuation. Where is the diminishing returns? Can I significantly change the profile of a beer with pitching rate(requires a taste test)? What truly is the "ideal" pitching rate? My neurons are tingling, I better stop

 

[Bobby_M]

Well, my control was about 1 quart with 7 grams of yeast. That's like 14 packs of dry yeast in a 5 gallon batch and it only went 4 gravity point further. I wouldn't use a larger pitch simply for the attenuation benefits. However, if you're in a hurry, it ferments out really fast. It was clearing already at 32 hours.

 

[Ryan_PA]

I was under the impression that o2 did not decrease lag time, but rather promoted more, healthy yeast growth.

 

[kenb]

Ok maybe i missed it, but what is the difference in the control batch vs the others, and why did it have so much lower of a FG?

 

[shafferpilot]

Ok maybe i missed it, but what is the difference in the control batch vs the others, and why did it have so much lower of a FG?

It was way over-pitched.

 

[kenb]

It was way over-pitched.

Was it dry or rehydrated?
O2 or not?
How much overpitched?

 

[Bobby_M]

It was rehydrated, no O2, 7 grams in 1 quart. Normal pitch rate is 11 grams in 20 quarts (.55 grams per quart) so it's like 14 times overpitched.

 

[Kaiser]

Ok maybe i missed it, but what is the difference in the control batch vs the others, and why did it have so much lower of a FG?

It basically comes from the fact that yeast doesn't stop when all the fermentable sugars are gone but oftentimes stops before that point. This is normal and a function of the yeast strain and feementation conditions. I wrote about it here.

Kai

 

[korndog]

I'm highly in favor of having this experiment repeated by others both with the same conditions and with other variances. If I get the ambition up again, I might try a higher gravity and slightly lower pitch rate to simulate a vile/propagator pack direct pitch.

I'm reluctant to try bottling the samples because I suspect all the sample taking may have introduced some oxidation. Maybe not. I suppose I can fill two bottles per sample and just drop 3/4 tsp of sugar into each bottle.

I'll try to have two tasting sessions in January where I can get a few local brewers to blind taste test and take notes.

I would be very interested to see results for Safale 05 with a high gravity wort in the 1.080 range.

 

[ScubaSteve]

As has been mentioned, this experiment is only valid for this type of yeast....but let me add that using o2 was probably irrelevant and probably a hindrance due to the fact that dry yeast is packaged with optimal glycogen stores, etc. and does not need the o2 to reproduce. When using liquid yeast, O2 definitely has its place...but again...if you've already been adding it to your starter, you probably don't need to add it to your wort because the yeast has already taken up most of the o2.