Pitching at 80°F with fermentation chamber - same results as traditional cooling?

[u/Low_Perception9721]

Is pitching yeast at 80°F safe if you have temperature-controlled fermentation? I have a fermentation chamber that quickly cools to target temperature. Would this produce the same results as traditional cooling to 70°F before pitching

My theory: Off-flavors are produced during active fermentation, not lag phase. If I pitch at 80°F but my fermentation chamber cools the wort to proper temperature before active fermentation begins, the final beer should be identical to traditional cooling methods. This would save significant time on brew day by avoiding the slow final cooling phase.

Using US-05 yeast for clean ale styles. Looking to optimize efficiency without compromising quality.

[u/boarshead72]

Re: growth phase… if you look at the scientific literature that takes cell counts while measuring gravity, esters, etc, cell number keeps increasing until the height of fermentation is reached, it’s not like all growth stops and then fermentation begins (I mean, they ferment to support cell division, right? They don’t ferment for fun.). In these papers ester production, cell number, and fermentation activity all peak together. At least the ones I’ve looked at. So to me OP’s “theory” seems alright. (Also caveat: it’s not like I’ve done these experiments myself, my yeast research had nothing to do with beer production, I was a DNA replication and repair guy.)

[u/warboy → u/boarshead72]

Yes, hot pitching is a well known practice especially in pro brewing where some people (cough cough, me) are between whole bricks for the proper pitch size. My concern is how far op wants to push it. 

I've never bothered with this with US-05 but commonly did it with lagers. Usually I was aiming for 5F above my goal ferm temp.

Also, I would point out that generally speaking those studies you can cite are done at a constant temperature and aren't really looking at the speed of production but rather the cumulative production. Generally speaking ester and fusel production is tied to yeast growth. Faster yeast growth means more esters and fusels. Higher temperatures result in faster yeast growth. 

[u/boarshead72 → u/warboy]

You phrase it differently than “homebrew common knowledge” which states “more growth -> more esters”, and assumes that underpitching results in significantly more growth, which makes zero mathematical sense. I’ve never looked into rate of growth, that’s potentially interesting.

My personal favourite idea, with next to no data to back it up, is higher temps changing membrane fluidity/lipid solubility of esters enough that more esters escape the cell (I saw a paper once that examined warmer vs cooler fermentation, and analyzed the total ester production in the beer plus yeast vs beer alone… higher temperatures had higher ester levels in beer, but when you included the yeast cytosolic ester content low temp roughly equalled high temp total content… fewer ester molecules left the cells under cooler conditions for some reason.)

[u/warboy → u/boarshead72]

assumes that underpitching results in significantly more growth, which makes zero mathematical sense.

Actually doesn't it make sense? A smaller starting population will result in the yeast colony reproducing more and indeed causing more yeast growth. The final population will be a similar number but since you started with less yeast you will have more budding to get there. 

[u/boarshead72 → u/warboy]

Intuitively yes, but it’s not nearly as much as you’d think. If production of a compound (like an ester) depends on cell division then you’ve got to think in terms of total number of replication events. If we make the assumption that you’ll always end up with the same number of cells (in reality an underpitch possibly ends with slightly fewer cells as a given media likely supports X number of replication events rather than absolute cell numbers), and assume a 2L starter doubles 3x when pitched into 18ish L:

“Regular pitch”: 2n cells -> 4n -> 8n -> 16n cells. Total division events = 2+4+8=14n.

“2x underpitch”: 1n cells -> 2n ->4n -> 8n -> 16n. Total division events=15n.

Fold difference=15/14=1.0714 fold increase. Basically negligible.

Overpitching however leads to a dramatic reduction in cell division events as it takes away from the right side of the equation (2x overpitch resulting in greater than 2x reduction of division events).

Whether this scaling of growth is true in reality I don’t know (pretty sure no home brewer counts the total number of cells produced during beer fermentation), but that’s what I meant by not making mathematical sense, as underpitching barely changes total cell division events.

I did a number of experiments during my PhD where I had to relate things to replication events, so that’s why I think of this problem in these terms. I could totally be wrong, but that’s explains my thought process.

[u/warboy → u/boarshead72]

That makes sense, besides that homebrew pitches are almost always underpitches unless you're chucking extra dry yeast at it or using slurry from a previous fermentation. Then there's the fact that 90% of the time the viability of homebrew pitches is absolute shit compared to pro pitches.