I just brewed a 5 gallon batch of a Dubbel. Made my own D-90 which tasted pretty good. The mash and boil went swimmingly. Cooled, transferred to the fermenter and oxygenated with pure O2 since the OG was 1.072. When I went to pitch my Wy 1762 starter I took a quick sniff and it smelled strongly like vinegar. Dumped it. With LHBS closings, the nearest is 2 hours away, so my only option at that point was to use two sachets of dry yeast I had, both a year past expiration date, one BE-256 and one LalBrew Abbaye. They were cranking away the next morning, about 16 hours in.
Question is, since the dry yeast has no need for the oxygen in the wort, does it get consumed at all during fermentation? Have I unintentionally created a cold side oxidation issue? I might add some ascorbic or SMB at packaging, but I have read that the Belgians benefit from some oxidation during aging.
The yeast will use the O2 to synthesize sterols, which keep cell walls flexible to encourage yeast budding.
Dry yeast may not NEED oxygen, but they will happily use it if you give it to them. Your beer will be fine.
Why would you do it if it didn’t need it? The yeast is coated in sterols and additional O2 will not be utilized.
Yeast won’t spend energy synthesizing molecules they don’t need. Dry yeast membranes generally have all the structural materials they need, but for a 1.072 wort, the yeast probably assimilated some of that added O2. But a lot of it would not have been assimilated and would go to oxidative reactions. These might reduce the shelf life but I’m sure your beer will turn out fine. Adding stuff at packaging won’t do anything about the oxygen added at pitch; that damage will already have been done.
Your starter was infected with Acetobacter, maybe also wild yeast if air got into it after it was finished.