Re-oxygenate, or Let it Ride

[John Sand]

I brewed my Going to Hell IPA yesterday, pitching the Bootleg Brulosophy yeast last night after it cooled. It's slow getting started, which happened last time too. The thing that concerns me is a small change in my process. For five years of brewing I have oxygenated the wort by aggressively pouring it into the fermenter. Last year I got a new kettle, a 15+ gallon SS beauty with a nice tri-clad bottom. I love it, but it's heavy, especially full of wort. Just recently I added silicone hose to easily fill the mash tun, or the fermenter. That works nicely, but halfway through filling the fermenter I realized that it wasn't splashing much. I raised the hose and got some foam, then poured the last of the wort standing. Now I wonder if there's enough oxygen for yeast health. The good news is that I pitched 8oz of month old slurry, so I didn't start small. OG was 1.061. What do you think?

[HerbMeowing]

What do you think?

RDWHAHB.

Then again; let it ride ... bottle it up and send it to me (post-paid).
I'll let you know how it turned out.

[dbrowning]

is that a legitimate concern?
Serious question?

[mashani]

Herb doesn't have the proper disposal facilities. I do. Send it to me for proper disposal.

That said,

So the reality of it is that without enough oxygen your cell growth will top out at some value where … they run out of nutrients necessary to grow … if it's oxygen that runs out first, then that's when they stop making new daughter cells, and at that point the yeast have no choice but to switch to active fermentation.

That is why continuous oxygenation of a starter produces the most cells, because the yeast will grow until they run out of some OTHER nutrient. It's why when we grow things in labs we use stir plates and nutrient rich growth mediums when we want to get the most out of it.

But if you follow this, then actually "active fermentation" will happen sooner if there isn't enough oxygen at identical pitch rates. If you see it krausening, the whole metabolism has changed.

It may not be a very vigorous seeming fermentation though because there potentially aren't as many cells having a party in there.

It will still ferment out as long as the yeast doesn't get stressed out and go belly up, it will just take longer, and ester production might increase.

Pitching more yeast gives you more cells to start with, but doesn't necessarily mean more cells overall before fermentation starts. Each growth phase is gonna chew up oxygen and nutrients, and if you pitch a lot more yeast, then each growth phase is a lot bigger, so each growth phase requires more nutrients and oxygen. Growth phases are exponential, but again when they run out of any nutrient necessary for growth they are going to change metabolism and start actively fermenting with whatever cell count is there at that time.

This is why you can have good results with a shaken starter vs. a spun starter or even a direct pitch as long as your wort has enough oxygen and nutrients. It just takes more growth phases for it to start "doing it's thing". Because of that there is more chance for other organisms to get into the initial mix, and more potential for ester production (wanted or not), or other stuff like acetaldehyde production, etc, because it requires more growth phases, so "lag time" is bigger. Other then that, it really doesn't matter and it will most likely all clean up given time.

A wort with a smaller yeast pitch and large amounts of oxygen and nutrients actually can have MORE lag time (before you see active fermentation signs) then the same pitch with less oxygen or nutrients. Because it simply can't grow and has to switch metabolism.

You might not see this with a big pitch because 2-3 growth phases might chew up everything regardless due to the initial cell count being so large.

Dry yeast does better with reduced oxygen levels because it contains (as in it is pre-packaged with) some of the things that the yeast need oxygen to make for growth.

In any case, at this point if it's already actively fermenting, let it ride, as the yeast are operating in a different type of metabolism now then growth phase, and oxygen isn't gonna do much good, and might even be bad.

I pitch a hella lot of yeast in very well oxygenated wort to get "better beer faster", but not necessarily to get "better beer if I waited longer to drink it". It's mostly my acetaldehyde super tasting that is the issue if I don't pitch a lot, but I also really like being able to turn around dubbels and triples and bocks and such 4 weeks in the bottle instead of 3 months in the bottle.

[John Sand]

Well, this morning it is bubbling fast and steady, about 32 hours after pitching.
Last time it was about the same amount of time, and the starter was active when pitched. I would say this is consistent performance, though the temperature is a few degrees warmer.

[Inkleg]

Thank you Dave. That was an interesting and educational read with my coffee this morning.