The Jamil & Chris White "Yeast" book indicate that "too much oxygen" can increase fusel alcohols & acetaldehyde and will reduce ester production, but they don't indicate what "too much" means. They do state that "too much oxygen" is rarely a problem and suggest 8-10 ppm for most yeast. Keep in mind a couple of things here.
1. The "right amount" is a function of pitching rate. If you're just pitching a single vial/pack of yeast, I suspect it's easier to have "too much" oxygen than if you're following the pitching rate guidelines & making a starter.
2. For most beers, I seriously doubt any of us are over-oxygenating. I've been tracking DO for various means of aeration for the past year & have found it damn near impossible to get more than 16 ppm DO with an oxygen bottle & diffusion stone.
3. Any amount of DO over 8 ppm will gradually dissipate as the solution will have more DO than is possible with air & the excess oxygen will equilibrate to atmospheric conditions. I'm not sure what the dissipation rate is, but I bet it will approach 8 ppm during the yeast growth phase.
I probably have enough data to do a Tech Topic on aeration methods if you guys are interested. I only have a couple of data points using an aquarium pump, but it seems very consistent so far & is probably safe to share. I have 10 data sets for the "purge & shake" method & 10 for the "O2 bottle & aeration stone". There is some variation, but I think there's enough data to show a meaningful trend. I would like to follow this up with a "how much do I need?" set of experiments.
If you're getting yeast-derived off flavors, I would look at pitching rates & temp before oxygen (assuming you're aerating at all).
On Saturday, April 13, 2013, bf514921 wrote:
i remeber a few times on he jamiel show talking about over oxegytion. I dont oxegrnate, but remeber the "fuelsol and hot satement"
Brandon Franklin - The other Franklin
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