Dry Yeast Rehydration and O2 experiment

[Lil' Sparky]

Another nice experiment and video, Bobby!

 

[DUCCCC]

Thank you very much Bobby, that was a fantastic video!

Matt

 

[Funkenjaeger]

Absolutely awesome, thanks! Your video will serve as a great reference to show the benefits of rehydrating dry yeast, a step so easily (and often) skipped, despite being really easy.

I was surprised at how significant the difference was between the control and the rest of the samples - the faster fermentation I expected, but the significant difference in FG was rather surprising. I figured there'd be a bit of difference, but I would have thought the rest of the samples would have caught up a bit more given enough time. So, I think your video will also serve as a great reference as to why you should pitch a lot of yeast! (suddenly my 1L starter flask seems small, especially in light of my recent issues with poor attenuation... time for a new toy!)

 

[Bobby_M]

I realized it might be hard to comprehend some of the tables as the video is running so here are the tables:

12 hours - in case you can't read it; Control, 02+wet, 02+dry, no O2 wet, no O2 dry.

20 hours

 

[Ryan_PA]

So based on this, which will you use in the future?

 

[clayof2day]

I agree, great stuff. I do have to interject one constructive criticism. These results can ONLY be applied to Danstar Windsor. These results cannot be extrapolated to any other dry yeast until we have shown 1.) repeatability and 2.) that the trend holds true with other dry strains. This beast of burden should not fall squarely on Bobby's shoulders, either. I think the video provides a great resource, like a lab notebook and now we could all repeat this if needed and present excel data similar to what he has done.

Gread job setting the standard, Bobby

 

[Sea]

Great vid/experiment Bobby!

One question:

Are you going to compare flavor? I ask because I was under the impression that oxygenation is intended to create a healthier environment for the yeast to begin fermentation in, as an oxy poor environment may cause the yeast to produce off flavors while reproducing prior to beginning fermentation. am I correct about this? If so, I would think that the most important factor would be taste?

Can you tell I have yet to acquire any type of oxygenation setup?

 

[Bobby_M]

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.

 

[Bobby_M]

Great vid/experiment Bobby!

One question:

Are you going to compare flavor? I ask because I was under the impression that oxygenation is intended to create a healthier environment for the yeast to begin fermentation in, as an oxy poor environment may cause the yeast to produce off flavors while reproducing prior to beginning fermentation. am I correct about this? If so, I would think that the most important factor would be taste?

Can you tell I have yet to acquire any type of oxygenation setup?

As far as I can tell, the only reason to use oxygen is to get yeast to reproduce to grow the colony. Given an already high cell count in a rehydrated dry yeast pitch and a similar OG of 1.050 give or take, I don't think there will be any taste difference with O2 or not. Jamil Z has suggested that big slurry pitches will ferment a batch out just fine but will be missing some flavor profile that yeast growth imparts. I'm not so sure. Biermuncher mentioned his local brewery visit where they WAY overpitch and make really good beer in short time.

For now, if I brew something under 1.060 OG and plan to pitch dry yeast, I MAY skip the O2. One thing I will more aggressively disagree with is any suggestion that O2 "reduces lag time". It couldn't be further from the truth.

 

[david_42]

will be missing some flavor profile that yeast growth imparts

This is only true for a few yeasts/styles. One of these days, I'll find my list.

Neutral yeasts work best in bunches. I agree about O2 increasing lag time, with more O2 the growth phase becomes longer. The higher population catches up eventually.

 

[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.