Ask Mr. Wizard

Over-Oxygenation of Wort


Andrew Willing - Minneapolis, Minnesota asks,

In the May-June 2013 edition of BYO, Jamil Zainasheff discusses the Belgian blond style. At the very end of the article, he discusses "oxygenation" (i.e., with pure O2, as opposed to "aeration" with air) and states that (a) over-oxygenation of wort at pitching can result in fusel production, presumably outside of any other factors or variables; which obviously also suggests THAT (b) over-oxygenation of wort is even possible. Jamil goes on to suggest an oxygenation rate of 1 L/min for one minute.First, is (b) true? Is over-oxygenation of wort even possible? I've read on a number of forums and other places — though, unfortunately, none available to cite at the moment — that speculate that over-oxygenation of the cooled wort (at pitching time) is *not* a reasonable concern. The thought is that the solubility of O2 in the wort is limited, and that any possible over-saturation would likely leave solution within short order.Second, if (b) should be true, I have never read anything (else) that suggests a link between fusel production and oxygenation. Everything I've read suggests fusel production is a result of poor fermentation temperature control. Is there any support for Jamil's oxygenation claim? Is there any known oxygenation rate (i.e., in contrast to the cited 1 L/min for one minute) that will lead to noticeable fusel production, even with tightly controlled fermentation temperatures?I ask because I do oxygenate my wort, and have for some time, but my regulator does not have a gauge by which I can measure flow. If this is more than a theoretical issue, I may need to invest in some kind of flow-metered regulator. 

I have been writing this column for nearly 18 years and I think I have been writing about the importance of wort aeration for nearly the same time period. While oxygen is
Response by Ashton Lewis.