Sodium Metasulphite For Chloramine Removal

[manticle]

No dramas. I'm typing on a phone so briefer than I intend to be. Question was fair enough.

 

[Wolfman]

Brewing a Belgium pale, dry stout and a Porter tomorrow. Will add some sodium Met to see if it makes a difference.

I still welcome a healthy discussion on this topic though.

 

[Parks]

Like I said I went to buy some campden tabs but on the packet it said "0.5g sodium metabisulfate". So my guess is 0.5g?

Did you watch the video Parks?

Yeah mate, he's pretty easy to listen to actually.

I am really after a specific "add x grams to remove y PPM chloramine/chlorine". I have been using the "pinch of sodium met" method but I thought I may have added too much.

RE chloramines being a problem - I did an English IPA recently before i started using Sodium Met which stunk of bandaid / rubber. Investigation suggested that chloramines are the most likely cause.

 

[treefiddy]

In theory, 1.34 mg of sodium metabisulfite will remove 1.0 mg of free chlorine. In practice,
however, 3.0 mg of sodium metabisulfite is normally used to remove 1.0 mg of chlorine.

Assuming Brisbane water is 6 ppm (mg/L) chloramine, there would be 0.12 g in 20 L.
So 0.16 g of metabisulfite minimum, 0.36 g maximum.

 

[kymba]

I was cleaning the fish tank last night and thought of this thread...supposedly, sodium thiosulphate the active ingredient in water aging stuff knocks out chlorine and chloramine instantly. Anyone know if this could be of any use to us brewers?

 

[drsmurto]

Firstly, I don't understand why you would add a reactive chemical like the metabisulphite ion to your mash if you are not using it to react with another compound. That makes no sense to me.

Secondly, for the metabisulphite ion (S2O52-) to react with a chloramine, it first needs to dissociate into the sulphite ion (SO32-). This is a pH dependant equilibrium. The lower the pH, the more sulphite you get which is why winemakers have to take pH into account when adding it to wine as the higher the pH of the wine, the more metabisulphite they need to add to get SO2 (which is in another pH dependant equilibrium with SO32-) which then protects the wine from oxidation and bacterial spoilage.

The problem you face as brewers is the pH of the mash is ~5.2-5.5 and so the equilibrium is drastically slowed down - ie. the dissociation becomes less favourable and so you need to add a lot more to achieve the amount of sulphite you need to react with chloramine.

Of course, all of this assumes you are doing this in a nice, aqueous solution, not a complex matrix of crushed malt and water. The higher temperature will also change the equilibrium.

So the numbers quoted in this thread and taken from somewhere else are stabs in the dark. I suspect most are adding it in excess.

The other issue you face is that if you do add an excess, once you separate the liquid from the mash and start boiling it, the pH decreases. So any excess metabisulphite in solution is now sped up in its dissociation to sulphite. Sulphite is not volatile, it is an ion and so will not be boiled off.

You are left with the very real possibility of sulphite in the wort when you pitch the yeast. Why is that an issue? Yeast use sulphite as well as sulphate to synthesise the sulphur containing amino acids they need. One of the by products of this synthesis is H2S - hydrogen sulphide. Yeast strains vary in the amount of H2S they produce, how much of it is used up to produce the amino and how much they release into the wort. I have not met anyone who likes the smell of H2S.

Hope that is of some use. Happy to continue this discussion and help destroy some of the myths and give you a better understanding of the science. Sulfur chemistry is what I get paid to do.

 

[benno1973]

Great explanation, thanks for that. The only thing I'd mention is that you're talking about adding it to the mash, but the general theme is treating HLT water prior to mashing, which means an aqueous solution with a higher pH. But really interesting about the H2S, maybe I should try reducing the amount I add, or just springing for a filter instead...

 

[Parks]

No one is adding it to the mash directly I don't think. The reading suggests the metabisulfite reacts very quickly in water to break down the chloramine - is this something you suggest is wrong?

 

[slash22000]

From what I've heard, you add 1/4 of a tablet to the mash water, before the mash. Apparently it only takes a minute or two before it's finished. Removes chlorine and chloramine.

I don't know jack about the science, but if you Google it, you'll find hundreds of brewers doing it worldwide, so even if it doesn't really help, I guess it doesn't hurt?

 

[drsmurto]

If you are adding it to water then the reaction is a few orders of magnitude slower again.

EDIT - that doesn't mean the reaction won't take place but it will be much slower. If you think it is removed in minutes (and I'll assume you are at least smelling it to check that it has in fact done what you think it has done) then you have added vastly more than needed. Much lower quantities left for a longer time would be a safer option.

 

[benno1973]

If you are adding it to water then the reaction is a few orders of magnitude slower again.

Ahh, I see. I just re-read your original post, so that makes sense. I tend to leave it overnight, and there's no chlorine smell, but I still may be adding way too much. The last beer I brewed was a simple pale/wheat with Mosaic hops and has a slight eggy smell and taste. It was confusing because it was a US05 yeast which generally doesn't contribute this, so I'd chalked it up to infection. Still could be, but I guess there's another option given what you mention about H2S.

 

[mabrungard]

Adding metabisulfite to your brewing water BEFORE ADDING ANY GRAINS is a relatively harmless practice if you limit your dosing to the prescribed amount. You have to perform this treatment before adding the grain since chlorine compounds react almost instantly with wort compounds to create those chlorophenols that create the mediciny taste and aroma in beer. You need to neutralize those chlorine compounds first.

The one campden tablet per 75 liters of water dosing rate is based on a chlorine or chloramine residual of 3 ppm. That dosage is stoichiometrically derived and should leave very little sulfite residual in the wort. I noted that someone said that one water supply quotes 6 ppm. That would require double the dosage.

Even if there is a bit of excess metabisulfite added to the brewing water, unreacted metabisulfite is very unstable at high temperature and the boil should break down and drive off the excess.

As mentioned above, if your water supply uses chlorine, there may not be a need to neutralize the sparging water in the HLT since the chlorine MIGHT be driven off by the heating. But its a big IF. I suggest that treating all brewing water before heating is a wiser choice.

 

[Niksko]

I'm currently grappling with this issue in Melbourne.

I brewed an IPA about 2 months ago, and every bottle I've opened has had a slightly medicinal taste. I've also experience the exact same flavour in some of the beers my dad has brewed.

I dosed the strike and sparge water for my currently fermenting beer (also an IPA) with potassium metabisulfite, so fingers crossed I can get rid of this taste.

 

[manticle]

I doubt it's melbourne water.

Either an infection or you are using a chlorine based sanitiser and not rinsing correctly.

 

[Wolfman]

Mants, do you have the latest Melbourne water report?

 

[slash22000]

Water reports should be freely available to you, Wolfman. Get in contact with your water supplier and they should be able to provide you with one, they probably have it on the net to download.

 

[manticle]

Can't post the link at the moment but google 'typical water analysis melbourne'. I think the most recent is 2012.

Somewhere in my email I have the two reservoirs that service your area. I'll have a look.

 

[manticle]

Brunswick east is supplied by silvan and winneke.

 

[slash22000]

Recently came across this study in chlorine/chloramine removal from brewing water: http://hbd.org/ajdelange/Brewing_articles/BT_Chlorine.pdf

There is a wicked amount of chemistry all through there, but page 17 has a fairly simple table that compares various methods of chlorine/chloramine removal. I quote:

"When Campden tablets or sodium metabisulfite are used, all chlorine and chloramine are converted to chloride ion in a matter of a couple of minutes."

This is with adding the recommended amount of 1 tablet per 20 gallons.

 

[technobabble66]

Recently came across this study in chlorine/chloramine removal from brewing water: http://hbd.org/ajdelange/Brewing_articles/BT_Chlorine.pdf

There is a wicked amount of chemistry all through there, but page 17 has a fairly simple table that compares various methods of chlorine/chloramine removal. I quote:


This is with adding the recommended amount of 1 tablet per 20 gallons.

V interesting. Great find.

Note that boiling is also moderately effective: Taking an hr to get 10L to boil roughly halved the chloramine levels, & then an hour of boiling comes close to full removal of chloramine.
However, that's opposed to the Campden tablets (potassium/sodium metabisulfate) which halves chloramine in under a minute, close to full removal in a few minutes.

For that study, 1 tablet = 695mg of roughly pure potassium metabisulfate.
If using sodium metabisulfate, you'd use about 15% less. Though that's an insignificant difference to really stress about.

That's 1 tablet per 20 gallons, assuming the chloramine levels are 3mg/L, and there's no free chlorine.
Free chlorine needs about half the amount of tablet per mg/L.

Page 23-25 has the detail about Campden tablets.

Also,
"Our recommendation of 1 Campden tablet per 20 gallons is designed to cover this nominally “worst case” of 3 mg/L chlorine all as chloramine. In most cases this will be more than required and there will be sulfur dioxide left over after the chlorine has been reduced. Some of this will be driven off when the wort is boiled but some of it will react with organics in the mash reducing them. This results in the formation of “reductones”, i.e. reduced state sub- stances which are considered desirable as they are supposed to prevent oxidation and staling. In reducing organic material in the mash, the sulfur dioxide is converted to sulfate. If all of it undergoes this fate then the maximum found in a brew made from water treated with one Campden tablet per 20 gallons will be about 8 mg/L as calculated above."

"A another convenient rule of thumb is a refinement to the 1 tablet per 20 gallon rule. Add twice the chloramine value to the free chlorine value and divide by 6. This is the number of tablets required for 20 gallons. Scale this value accord- ing to how many gallons need to be treated."

"To add fractional tablets, dissolve, or rather suspend, a tablet in 100 mL of water and, just after agitating, measure out the number of mL which corresponds to the percentage fraction required. For example, if a third of a tablet is required, measure out 33 mL."