Injecting Pure Oxygen and Effect on Fermentation

[PeeBee]

(EDIT: On preparing this post and rescalling all the graphs to a common layout, things don't look as bad as I first judged. But I've posted anyway because others thinking of doing a similar switch to pure oxygen and liquid yeast might find my experiences useful).

I made a common no-no and am fighting the consequences. I made TWO major changes to my brewing procedures: Firstly I started using pure oxygen in place of an electric tyre pump, bacterial filter, and sintered SS stone (the latter I kept to use with the oxygen). Secondly I switched to using liquid yeast.

Here's a log of what I'd grown to expect, a medium gravity best bitter, using S-04:

Here's my first attempt with the changes; I could only find advise to inject oxygen for 1 minute into 25L, so I gave 45L a 2 minute blast. I also grew up the yeast for 1-million-cells/ml/degree-Plato as recommended for a beer of OG 1.065+:

I was moderately surprised by the speed of fermenting such a strong beer and that it overshot the anticipated FG. But having rescaled the graph for this post it doesn't look so bad. All the same for the next brew I cut back on the oxygenation (90 seconds instead of two minutes) and grew up the yeast for 0.75-million-cells/ml/degree-Plato the beer having slightly lower OG (1.058), and the result:

Hum, that has well overshot the expected FG and stopped pretty suddenly. I read to expect a more complete fermentation using pure oxygen, but I wasn't expecting such a big impact on attenuation. And a 1.058 beer fermenting out in 48 hours, that is quite exceptional in my experience.

Could I be going a bit overboard with the oxygen? Could I be culturing up the yeast a little excessively? I'm aware most of the information I'm depending on is American and they like clean complete ferments. Should I hold back on the yeast culturing, say 0.5-million-cells/ml/degree-Plato? Should I not surpass 1 minute for injecting oxygen, maybe use even less?

Thanks

[MTW]

It's interesting stuff, thanks, but it would be good to know a bit more. I've never used anything other than splashing and a spoon, and your attenuation looks moderate at best, if I'm reading the graphs correctly; maybe 71% on the first liquid yeast brew and 74 on the last? I wonder if the decreasing temperature has a part in that. Mine are only ever taken upwards (applying heat) until FG is reached.

What was the yeast, approximate grain bill, mash temp? As you say, you've changed more than one variable and it's not a white-coat job, but just to figure out the info it would be good to know a little more.

PS, what's the sky blue area showing?

[PeeBee]

It's interesting stuff, thanks, but it would be good to know a bit more. I've never used anything other than splashing and a spoon, and your attenuation looks moderate at best, if I'm reading the graphs correctly; maybe 71% on the first liquid yeast brew and 74 on the last? I wonder if the decreasing temperature has a part in that. Mine are only ever taken upwards (applying heat) until FG is reached.

What was the yeast, approximate grain bill, mash temp? As you say, you've changed more than one variable and it's not a white-coat job, but just to figure out the info it would be good to know a little more.

PS, what's the sky blue area showing?

About 73% on both, but the yeasts weren't high attenuators. Wyeast 1099 for the first (okay, that just about scrapes into expectations), and White Labs WLP002 for the second.

I used to splash about with a spoon, until I got the conical fermenter which has stir unfriendly projections. For a while I aeriated with a pump, filter and stone, but that was a real pain and needed 20-30 minutes with a very noisy tyre pump (forget aquarium pumps for SS stones and 40-70L fermenters) - oxygen is 1-2 minutes. Both mashed slightly low (64-65C) which would account for being at the high end of published attenuation, but doesn't suggest it should greatly exceed the published figures. All malt grain.

Temperature control fitted to the fermenter, so I forced the temperature to drop at the end. I don't hold with all that keeping the temperature up and getting the "yeast to clean up after itself". They're all "Americanisms" for making American beers.

The "blue" area on the graph comes from Beersmith software (which created the graphs) - it just provides a guide for temperature control.

[MTW]

Great, thanks. Knowing those yeasts were used certainly clears up what could otherwise be thought of as low attenuation. My main reason for raising the temperature is just to dig out any undiscovered attenuation, not so much a clear up; 002 is certainly prone to that, but that's another topic. I don't think it's just an American thing anyway, but I get what you're saying.

I guess it's the resulting taste of the beer I'd be most interested in, as I haven't had to inject oxygen to get attenuation or a prompt fermentation. That said, 2 days is certainly fast! Do you inject oxygen in the starters by the way?

[PeeBee]

Great, thanks. Knowing those yeasts were used certainly clears up what could otherwise be thought of as low attenuation. My main reason for raising the temperature is just to dig out any undiscovered attenuation, not so much a clear up; 002 is certainly prone to that, but that's another topic. I don't think it's just an American thing anyway, but I get what you're saying.

I guess it's the resulting taste of the beer I'd be most interested in, as I haven't had to inject oxygen to get attenuation or a prompt fermentation. That said, 2 days is certainly fast! Do you inject oxygen in the starters by the way?

Starters are shaken, then stirred continuously on stir plates (yeap, plural, 45-70L litre batches and 2L flasks are quite big enough to carry so I need two) so no need to inject oxygen in the starters.

On the third example I could have added a third variable: I added recirculation to the fermenter - mainly for temperature control as it was to recirculate through a shelf cooler, but it would have introduced frequent gentle rousing which would affect attenuation. But I hadn't counted on the nature of WLP002 yeast which quickly bunged up my 12V Topsflo pump with its flocs so no recirculation (and a headache figuring out how I am going to get the beer into casks/kegs).

[JabbA]

Sorry, I've no experience in aerating with O2. But may I ask what you're using to measure the gravity and produce the graphs?

Cheers,
Jamie

[PeeBee]

Sorry, I've no experience in aerating with O2. But may I ask what you're using to measure the gravity and produce the graphs? ...

Refractometer, removing tiny samples from the sample tap on the conical. Temperature from an Inkbird ITC-308, which also controls the cooling - and potentially the heating if I needed it, which has a probe stuck inside a thermowell retrofitted to the conical (replacing the dial thermometer it used to have). Data is logged manually into Beersmith software which creates the graphs Then using Microsoft's built-in "Snipping Tool" to create the snapshots for posting here.