Sodium metabisulfite question

[Doctormcbrewdle]

Hi all. I'm wondering, Does sodium metabisulfite get completely driven off during the boil? Or does it remain active?

 

[MHB]

Interesting question
Short answer is going to be probably, given the sort of amounts used in brewing.
Its ridiculously soluble at 100oC, where it will break up into SO2 and Sodium Sulfite, the SO2 should be readily ejected at boiling temperatures.
Unless you have added heaps (100's grams), it should be all gone in the boil, don't breath the fumes... no fun at all.
Mark

 

[Doctormcbrewdle]

Reason I ask is because my beer has been off the charts good since I stopped using it. Though, I also overhaled other practices around the same time too..

 

[MHB]

Would depend how much you were using, assuming you are adding some to dechlorinate your water, we would be talking half a gram or so per 23L batch, if you were using heaps more that could cause problems. not necessarily with the SO2 but some of the breakdown products.
Mind you if you made a bunch of other changes I wouldn't go blaming the Met without a long hard look at your other processes.
Mark

PS - Its a useful chemical, but like many things sometimes less is more, salt in cooking, hops in beer...
M

 

[Lyrebird_Cycles]

Hi all. I'm wondering, Does sodium metabisulfite get completely driven off during the boil?

Yes.

It's a standard analysis in the wine industry to heat a sample for 15 minutes after the free SO2 is measured to drive out all the bound SO2. That part which has oxidised to sulphate will remain but there will be no SO2.

It probably wouldn't matter anyway, many brewing yeast produce SO2 during ferment.

 

[Doctormcbrewdle]

Which is another reason bottlers can never make as gooder product as keg packaging without secondary fermentation I guess because yeast priducing this inside a bottle stays in the bottle

 

[captsensible23]

When adding sodium metabisulfite to the strike liquor, what would be the go to rate?
Should I add the same amount to the sparge liquor as well?
Cheers

 

[Aksarben]

Well this is interesting. I never heard of anyone adding Sodium Metabisulfite to their boiling wort. In the wine industry, and where I work, we use liquid SO2 or KMBS which is Potassium Metabisulfite for juices before fermentation and post fermentation and also small mounts from 5-30 ppm to finished wines to keep them at a certain free SO2 ppm level according to Molecular 0.9 ppm, for keeping concerns.

Yeast do produce some SO2 during fermentation, but I don't think that you would ever notice it in smell or taste, as the actual act of fermentation literally boils off the free SO2 (not total). When I measure free SO2 on a finished wine it usually in the 1-3 ppm range, which is an insignificant amount. You're more likely to have hydrogen sulfide produces in secondary fermentation rather than more free SO2. In champagne (sparkling wine) production, where yeast and yeast nutrients along with sugar are introduced to the wine to be bottled, it produces not only alcohol but CO2 and does so according to how much sugar in g/l is introduced before bottling. However, when disgorging, (removing the settled yeast plug in the neck next to the crown cap) we have a dosage of either wine that has been sweetened with sugar, or straight wine (for dry sparkling) but it always has a pretty stiff dose of copper sulfate in it to bind with the H2S and prevent off odors later on when finally opened.

To the OP, any bisulfite that was added to water would produce the detectable Sulfur Dioxide if in present with any acids. This part is what sanitizes and also smells. During boiling there is 0 ppm of left over SO2 as it is quite volatile. Total SO2, will also be driven off by boiling.