Over the last week I've been reading practically every book and magazine I have so I can't remember which one or where I read it but it went into some depth about pH creeping up in the mash and how malt conditioning effected it. I do remember it saying that 2% moisture (misting) added to the grains about 15 to 20 minutes before crushing lessened the release of polyphenols. It also noted that polyphenols create some astringency. It also stated that the longer the mash water is allowed to stay in contact with the grain husks more polyphenols are created or released.
I don't know, I'm not a scientist but it makes sense to me and I believe it, especially after doing a couple of overnight mashes and having one which should have been right for my water come out fairly decent except for a finishing astringency. It tastes good while consuming it, has good mouthfeel going down but it dries my mouth afterward. Its almost like a bitter but its not really bitter. Its hard for me to describe it I guess. Anyway I'm dumping it because I can't bring myself to drink it anymore as I find myself anticipating the astringency everytime I do and I wouldn't give it to anybody either now.