I've been having trouble getting my Imperial Stout recipe to finish fermenting (one gallon batches). Some of you suggested I oxygenate, so I bought the Oxygenation Kit 2.0 from Northern Brewer. I used it for one minute after cooling to 70 degrees, then once more for 60 seconds after 18 hours. There has been zero activity through the air lock, and it's been five days. The longest I've had to previously wait for activity was 2 days. Did I screw up?
Too much O2 (even if it really was too much, which I doubt) wouldn't inhibit fermentation. How tight is your lid? What was your OG and how big a starter did you make? Have you measured the gravity after those 5 days?
OG was 1.113 Yes lid is on very tightly. I haven't taken any other readings due to no bubbles in air lock. I used 6 grams of US-05 Safale yeast.
That's about 120B yeast cells (if 100% viable), into a 1.113 OG wort. If this was a 5 gallon batch, that's severely underpitched. That could explain a slow start, but I'd expect something happening after 5 days. I've seen bucket lids that looked tight, but after being sealed all the way around with a mallet (gently), CO2 bubbles magically started flowing through the airlock. Are you using a bucket? I would recommend taking one. At least open it up and see if there is a krausen or the residue of one.
Too much O2 shouldn't inhibit fermentation, but it can be detrimental in multiple ways that should be evident in the final product. 120 seconds of pure O2 served at 1psi (and I'm pretty sure you used a lot more than 1psi and don't know how many psi you used) in a one gallon batch is likely 5-10x as much as you needed. I suppose it's possible a megadose of O2 could inhibit fermentation, but since you are probably the only person in the history of brewing to use 120 seconds of O2 at a rate greater than 1psi in a one gallon batch, you will have to tell us what happens for the benefit of brewing science.
I've used 120-ish seconds of pure O2 in some lagers and big ale worts. I estimated the flow rate at 1 Liter per minute. I haven't done the mental gymnastics to convert that to the PSIs needed to drive it.
Your batch was at least 5 gallons. His was a one gallon batch. "Estimated. Haven't done..." It's sounds like you have some experiments to perform and or some numbers to crunch. Get crackin'!
Missed the one gallon batch part. Also makes the use of a bucket unlikely. OP: Are you fermenting in a glass jug? If so, you should be able to see krausen/residue right through it. If there's none...what temperature is the wort at?
Just checked. It has a layer of krausen. Maybe I'm ok and for some reason things were delayed. I thought the oxygen would have speeded things up...
Oxygen beyond what the yeast need won't speed up anything, expect maybe oxidation (staling) of your beer. Fortunately, the more O2 you dissolve into your wort, the harder it is to dissolve even more. If you were getting no bubbles, but there is a krausen, that indicates a leaky seal. Either in the lid/gasket/bucket interface, or the airlock/gasket/lid interface. And it's a good example of why bubbles are a terrible quantitative indicator (and in this case a terrible qualitative indicator) of fermentation activity.
I do recall an experiment at a local HB club about oxygenation rates arising from an argument about the efficacy of aquarium set ups VS pure oxy set ups. We tried to over oxygenate a batch, under oxygenate and accurately oxygenate batches and see what the result would be. The over oxygenated beer tasted fine and very close to the properly oxygenated batch; but the mouthfeel was off in the over oxygenated batch. So there can be negative consequences it seems. Although this was a one off experiment, so take it for what you will. The under oxygenated batch had off flavors for sure. So you'd rather error on the high side rather than low IMO. Really the only way you could over saturate the wort with oxy and cause problems for the yeast is if you utilized a pressurized vessel. You can't really over saturate a liquid in an open system as O2 will just breath out of solution.
Wanted to also add this: You have to really overdo it to over oxygenate. Like 10 minutes full blast pure O2 through a .5 micron stone. And even then the worst that will happen is inhibited ester production and increased fussell and higher alcohol production with a slightly diminished mouthfeel. I've seen and heard so many arguments and debates about oxygenation rates and methods. Pure O2 through a .5-2 micron stone is the best method and what typically works best is about 1-1.5 minutes with the valve opened slightly until bubbles start to come out of the stone; opening the valve all the way just wastes O2. About 2 minutes with big beers @ 1.060 OG or higher. Shoot for just enough but not too much and you'll be golden. Without a method of monitoring dissolved oxygen it is all guess work really...
