I haven’t done any research into this but from a cursory review it looks like they may be using ascorbic acid in the mash to reduce the metal ions produced during the mash and that survive through to the finished beer. These metal ions are pro-oxidative and lead to oxidation of your beer.
I do the same thing by mash hopping with high AA hops, the acids “complex” those metal ions so they are no longer pro-oxidative (the binding sites are already occupied).
I do the same thing by mash hopping with high AA hops, the acids “complex” those metal ions so they are no longer pro-oxidative (the binding sites are already occupied).