Water for Marzen
Posted: Sun May 01, 2016 8:31 am
Sulfur itself can, IIRC, exist in oxidative states ranging from +6 to -2, so it can get complicated. Equilibria are going to be dependent on a lot of factors such as concentration, pH, temp, etc. Under normal mash conditions, we are referencing the oxidation of sulfite to sulfate. We theorize that, due to the mash pH, the sulfates then form an equilibrium with sulfuric acid (and possibly the short lived sulfurous acid), which is responsible for the very slight pH drop in the mash. I wouldn't be surprised if there is some interaction with peroxide, although oxygen has to exist in the superoxide form (which generally requires a catalyst, like copper or iron...hint, hint) to create it. Under the acidic conditions of the mash there are sufficient free hydrogen ions available, but I would be hesitant in thinking enough peroxide would be formed without the assistance of biological enzymes. It's not a stretch to consider that malt may have some of these enzymes, but we haven't really looked into it.