SMB levels you should target completely depend on how tight your process and system is. Assuming a semi-poor system, targeting about 40mg/l of SMB is a great starting point that should not result in excessive sulfur, and this should be fairly in-line with what the pdf suggests. With a much more tight system, you may only target 20-25mg/l levels. If you wish to ensure no residual sulfur (aside from yeast derived), then regardless of tightness of your system, target ~25mg/l levels (safe level). I personally believe there is incremental improvement with incremental change as you develop your own process and system.
I don't think you risk a dumper if you err on the side of caution; plus you get a glimpse into how it affects the overall final product. Then, next time you can choose to go heavier/lighter on dosing as you see fit.
Thanks. That's exactly the kind of info I was looking for.
Here's the science...
http://www.********************/wp-content/uploads/2016/11/Metals-and-Beer-Stability.pdf
The metals catalyze reactions that result in free oxygen (i think, it's been a while since i took chemistry but that's what it looks like to me).
Thanks for that. I will read it in more detail when I can, but a cursory skim of it looks like it focuses on the commercial scale.
I would be really curious to see someone do an experiment to quantify O2 uptake from a copper IC, since that is the most common copper appliance used by homebrewers (especially an experienced low O2 brewer who has a tight process and can more precisely isolate the variable in question - hint, hint, gauntlet dropped).
I don't doubt the chemistry, I'm just curious about its impact on our scale as opposed to a commercial brewery scale.
It's funny, because in one of my old early homebrew books (maybe even Papazian - I don't know, I'd have to look for the source), there was a
recommendation to incorporate copper, if possible due to the flavor enhancement it can provide. Oh how times change.
The suggestion is to not use a small amount of vienna or munich in a predominantly Pils beer because the flavors come through to strong.
Okay, that makes sense if that's the intent, but if that's the case, it wasn't phrased very well because it says they contribute "undesirable flavors", and it only references small amounts, which could be (was) interpreted as saying larger amounts are okay, but small amounts will just F things up. (for reference, the exact quote is:"Vienna and Munich malts blended in small amounts with Pilsner can add undesirable flavor elements as less Sodium Metabisulfite (NaMeta, SMB) is used").
What you say makes a lot more sense. Thanks for the clarification.
So would you think a half pound of Vienna in a Pils (5 gal) would present too strongly in a moderately low O2 brew?
Aaaaaand lastly, do any of you guys purge your transfer lines with CO2 prior to putting wort through them? I'm not sure its necessary, but I always do that when racking (and "purge-ish" my receiving vessels as well). It would be an easy habit t to ransfer.