Maybe somebody who knows more about this subject can explain what I really do not understand about their theory (maybe I overlooked the explanation in the paper). If oxygen creates unpleasant flavors or destroys pleasant flavors in the grain in a matter of hours in the brewing process then why do these reactions not occur during the days/weeks/months between malting the grain and brew day?
Is heat accelerating the reactions?
Is solubility a factor?
Are reactions worse with compounds in the interior of the grain? If so, what accounts for the lack of reaction with oxygen already within the grain?
A lot of reactions and molecular formation goes on in the mash due to the aqueous environment that we create. That can't happen in the kernel (except if its really wet, ala crystal malt). So the fact that this staling reaction doesn't occur in the grain in the months between malting and mashing isn't a surprise to me.
I see that the German Brewing group was not the first to pose this concern with oxygen: http://www.ibdlearningzone.org.uk/article/show/pdf/494/
, so I'm not dismissive of the premise. The thing is that keeping oxygen out of the mash and wort and avoiding this degradation is like the war on Terrorism. You have to win the battle against oxygen 100% of the time. That is a tough thing to do. And considering that it only takes minutes for oxygen to create this staling reaction, I'm not sure that we could ever avoid oxygen contact to a large enough degree to taste an actual difference in our beers.
I've reviewed the molar amount of oxygen in our tap water at mashing temperature and I recognize that it actually takes only a fraction of the metabisulfite amount that is recommended in the German group's article. But then I recognized that the wort is constantly subjected to potential atmospheric oxygen contact and I'm guessing that the excess meta is in there to keep up the protection. I can see that blanketing the mash and wort with another gas like CO2 or N2 could help avoid using up the meta dose. Fortunately, the excess sulfite in the wort will be volatilized to sulfur dioxide in the boil and it leaves the wort. So you don't have to worry about sulfite in your beer.