[erockrph]

Can Brewtan B be introduced just prior to dry hopping to chelate metals?

I've done this a few times after reading about the possibility of dry hops adding metal ions to solution. I didn't notice any difference, so I stopped doing that. Either the problem didn't exist in my beers, or the effects are too subtle to notice.

FWIW, BTB can actually be the cause of purple coloration. Gallotannin picks up a blue or purple tint when it reacts with metal ions (iron gall ink is an example of this). I see it pretty commonly after my treated mash water sits for the night. Thankfully, that coloration has never carried through to my final beers, but it is pretty strange to see.

[tjhannan7]

I am not sure whether this is related to your problem, but monophenols can also contribute to a greyish purple color, astringency, and premature oxidation, even in bottle conditioned beers. See the following article: https://www.morebeer.com/articles/Beer_Phenols. The article highlights many sources for monophenols in the brewing process.

Our problem seemed to be our water. We use carbon-filtered municipal (river-sourced) water that is very alkaline (pH ~ 10) and early in homebrewing I found that many of my lighter beers became quickly oxidized after bottling and developed a "purple haze." I always pH'ed my mash and adjusted accordingly, but never adjusted my sparge water. After some troubleshooting, I suspected that the high pH was at least part of the issue and started adding acid to my sparge water, and this problem largely went away. My two cents...

[hopfenundmalz]

I am not sure whether this is related to your problem, but monophenols can also contribute to a greyish purple color, astringency, and premature oxidation, even in bottle conditioned beers. See the following article: https://www.morebeer.com/articles/Beer_Phenols. The article highlights many sources for monophenols in the brewing process.

Our problem seemed to be our water. We use carbon-filtered municipal (river-sourced) water that is very alkaline (pH ~ 10) and early in homebrewing I found that many of my lighter beers became quickly oxidized after bottling and developed a "purple haze." I always pH'ed my mash and adjusted accordingly, but never adjusted my sparge water. After some troubleshooting, I suspected that the high pH was at least part of the issue and started adding acid to my sparge water, and this problem largely went away. My two cents...

Chalk one up for the old advice to acidify the sparge water to less than a pH of 6 to minimize tannin/polyphenol extraction in the sparge.

Did I just say chalk?