I use the purged keg technique.
I'm skeptical of HSA, but low DO on the cold side, defiantly worth some effort.
One challenge is dry hopping without exposing the wort to air. You could transfer from a pressurised fermenter to a purged keg with bagged hops in it, then after a few days transfer to a serving keg?
I'm also thinking about including a bag of hops in the fermenter from day dot, but there are risks with losing aromatics or over hopping.
Anyone got a solution that works for them?
I don't pre-boil the water mainly because I don't have time to boil and then cool but there is no doubt boiling will reduce DO. 100mg of sodium met per litre does help.Are people adhering closely to this method and pre-boiling their water?
And how do people "condition the malt prior to milling with 1-2% water by weight" ? (and specifically I'm wondering if I could rock up to my LHBS and ask to have it done there).
* Recommended to add 100 mg/L SMB. That will add 24 ppm Na and 76 ppm SO4 compounds.
I worked it out this way too, which effectively requires more CaCl2 to balance this additional sulphate - particularly in beers with roasted malts or moderate colour drier beers.Actually it will add 24ppm Na+ and 101 ppm SO4 2-. The SO4 2- comes from oxidation of SO2 so the mass of the extra oxygen must be counted*.
100ppm of SMS will add about 67ppm SO2, which will react with about 17 ppm of O2 if given enough time (100 x 32 / 190 = 16.8).
* This is a gloss for clarity. There's a hydration step in between.
Actually I'm curious about this - my original SO4 number was 96mg, but that was based on a 190mg addition of SMBS. Wouldn't the SO2 just gas off? And the SMBS decomposes in water to SBS so wouldn't really get the chance to be heated.Actually it will add 24ppm Na+ and 101 ppm SO4 2-. The SO4 2- comes from oxidation of SO2 so the mass of the extra oxygen must be counted*.
100ppm of SMS will add about 67ppm SO2, which will react with about 17 ppm of O2 if given enough time (100 x 32 / 190 = 16.8).
* This is a gloss for clarity. There's a hydration step in between.
Actually I'm curious about this - my original SO4 number was 96mg, but that was based on a 190mg addition of SMBS. Wouldn't the SO2 just gas off? And the SMBS decomposes in water to SBS so wouldn't really get the chance to be heated.
Na2S2O5 + 2HCl >> 2NaCl + H2O + 2SO2, or
Na2S2O5 + H2SO4 >> Na2SO4 + H2O + 2SO2
Na2S2O5 + H2O >> 2NaHSO3- (sic)
Which then, with O2 becomes:
2NaHSO3- + O2 >> Na2SO4 + H2SO4
So do we assume that half of the SMBS is being broken down by H2SO4 as well? It's still a 1:1 molar conversion from SMBS to sodium sulphate - and with which cation will the SO4 (from SO2) bond? Won't it still just gas off before it bonds to anything?
Aha. I've gone to Na2SO4 (sodium sulphate) + H2SO4 rather than the simple and logical 2NaHSO4 of sodium bisulpate.I think you have confused yourself.
The easier way to think of this is to ignore the cations, they aren't contributing to the reactions.
The metabisulphite anion (S2O5 2-) dissolves in water as the sulphite anion (2 x HSO3 -) if you look at the stoichiometry there the difference is H20.
The sulphite anion reacts with oxygen to form sulphate anion (SO4 2-). That's why we add it.
The H becomes a proton (H+) by donating the extra electron, we then drop it as we are ignoring cations, so the stoichiometric difference is O.
I mole of SMS weighs 190g. 2 mole of sulphate anion weigh 192 g. Therefore we get about 101% yield of sulphate anion if the SMS is fully oxidised
At normal pH there won't be enough molecular SO2 to matter: the pK is 1.53 so at water pH there is less than 0.001% dissociation.
Yes exactly - it's quite likely that with a lot of systems some of the sodium bisulphite won't be oxidised, hence my inclusion of CO2 purging, yeast/LME in the strike water and ascorbic acid so that I can reduce the SMBS. I'm more in the 20mg/L range than 100mg/L.Just a reminder to be careful with the sodium meta additions. It tastes pretty awful if there's much left in the finished beer - it reminds me of bottom-dollar cider.
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