Potassium Metabisulfite Question

[RPh_Guy]

One example of a brewing textbook:
Kunze Technology Brewing and Malting 6th English Ed. p 90.

Sterilization by Chlorination
Hypochlorous acid is formed by introducing chlorine gas into water. [...]
The equipment costs are low but harmful products (adsorbable organic halide, chlorphenol, trihalogenmethane and others) are formed when the water contains organic substances or phenols.

 

[Yooper]

What textbooks are you referring to specifically? It should be very easy for you to confirm your assertions with actual evidence.
Acceptance or practice does not mean correct or good science. Homebrewers do a lot of strange things that don’t really do anything and are based on false understanding and assumptions.

How many years have you been brewing? I've been a beer judge a long time, and have judged beers in competition that have chlorophenols. When inquiring into this, the brewers will mention that they brewed with tap water, but "low levels of chlorine". Many municipalities currently use chloramines, since they are more stable.

I understand that you know your stuff but maybe you haven't studied enough brewing science and texts to fully understand the interaction of chlorine compounds and the enzymatic activity of the mash, and/or the yeast's interaction during fermentation.

One of my favorite quick reads on this is a short article by noted brewing water chemistry expert @ajdelange: Water Filters | MoreBeer That's more about removing chloramines and why/how, but it answers the questions on why it needs to be done.

And an except from "Water" by Colin Kaminski and John Palmer may be helpful: Removing Chlorine from Brewing Water | My Fermentation

I know you keep saying that chlorine doesn't impact the mash, but that doesn't make it so. Brewers know it does, our brewing textbooks (which I can't post, because they are books and not available online) tell us it does, our tastebuds tell it does, etc.

 

[Yooper]

@barada83

@mabrungard is also a brewing water expert. You dismissed him, but maybe it's worth listening to him.

I know that homebrewers do indeed have some strange habits, but removing chlorine from brewing water isn't done because we have nothing better to do. It's because using chlorinated water makes beer taste bad, forming those chlorophenol off-flavors that are very distinctive.

You don't have to believe me. Try it. Brew an all-grain batch with chlorinated water, especially if the chlorine is in the form of chloramines. Brew one without. Taste them.

 

[barada83]

Just to clarify, in case it’s become unclear - chlorine should definitely be dealt with. It’s pretty easy too. You can do so though letting water sit, boiling, carbon filtration, or chemical treatment.

I don’t agree with the sentiment persistent in home brewing to chemically treat your water for chlorine and especially not for chloroamines if present. Adding sulfurous compounds to the complexity of beer as stated, can do no good. They don’t just disappear and sulfur is the basis for a lot of bad tastes, smells, and even health concerns. Treat it chemically as a last resort.

 

[RPh_Guy]

Adding sulfurous compounds to the complexity of beer as stated, can do no good. They don’t just disappear and sulfur is the basis for a lot of bad tastes, smells, and even health concerns.

You're way off the mark with these sentiments. A negligible amount of sulfate produced by dechlorination with sulfite will have zero effect on the beer.

 

[Yooper]

You're way off the mark with these sentiments. A negligible amount of sulfate produced by dechlorination with sulfite will have zero effect on the beer.

And idiots like me actually ADD it to my beer in the forum of gypsum to enhance my highly bitter IPAs.

 

[barada83]

Yooper - Thank you for the links. A lot closer to what I am looking for versus you’re wrong and and a troll. I wonder why they weren’t posted sooner during my rambling phase. I really am trying to keep learning and if something isn’t making sense I’m going to keep pushing until I get it figured out.

If you add metabi in excess quantities you will get sulfate and residual sulfites. So sulfates are ok, can be good or bad depending on purposes. It should be part of the thought process at the very least as to the effects even from just an experimental and repeatable view in your brewing. Sulfites might not be the same. Beer is not typically high enough ph where it exists as sulfur dioxide which is volatile and could come out during a boil. Here is an article as it applies to winemaking Improved Winemaking: Sulphur Dioxide.

And one on sulfites Sources and Impact of Sulfites in Beer | MoreBeer


I still am missing one thing. How, and in mechanisms, chloroamines form chlorophenols. Can anyone help me answer this? Because if they don’t, then you really don’t need to worry about sulfites in the first place.

 

[Yooper]

If you add metabi in excess quantities you will get sulfate and residual sulfites.


I still am missing one thing. How, and in mechanisms, chloroamines form chlorophenols. Can anyone help me answer this? Because if they don’t, then you really don’t need to worry about sulfites in the first place.

Correct- but we are adding minute quantities, and with the reaction that occurs, which is instantaneous, there is no residual sulfite to worry about.
https://www.homebrewtalk.com/threads/campden-tablets-sulfites-and-brewing-water.361073/
I'm NOT a chemist at all, but in one of my brewing chemistry classes, it was explained to me that the interaction between the enzymatic malt in the mash and the chlorine is what creates the precursors for the chlorophenols. I'm sure that you could find this info, but most of the really good papers/textbooks are behind paywalls so I don't have a quick and easy explanation.

The interaction with the yeast is very complex, and I barely understood it when it was taught to me and I'm way too far out of it to remember it, except "Chlorine, especially in the more stable form of chloramine, is bad for yeast". I imagine it's because chlorine will off-gas, while chloramines will not.

 

[Bilsch]

Yooper - Thank you for the links. A lot closer to what I am looking for versus you’re wrong and and a troll. I wonder why they weren’t posted sooner during my rambling phase. I really am trying to keep learning and if something isn’t making sense I’m going to keep pushing until I get it figured.

You essentially kicked open the door of the church and yelled.. god doesn’t exist. What did you expect to happen?

There are many learned people around here with a massive amount of combined brewing experience, which would be helpful to that learning thing you mentioned. And much like it was in school, works best if you listen more and argue less.

 

[RPh_Guy]

Beer is not typically high enough ph where it exists as sulfur dioxide which is volatile and could come out during a boil.

You mean low pH.

 

[barada83]

You mean low pH.

Good catch. Yes. Acidic / low pH.

 

[Yooper]

The original question:

So I have read some, probably not all, threads on PM/campden tabs being used to rid tap water of Chloramines. My question is if you add too much does the excess get boiled off or will there be residual yeast killing compounds still in the wort after the boil that would not allow fermentation after pitching the yeast and kill them?

The thing with forums is that we try to answer a question. This is the Brew Science forum, so of course we try to give answers that have a scientific basis and that often generates discussion and more questions.

But still, the idea is to answer the question, which was answered in the very next post:

Excess metabisulfite is decomposed during the boil, so you don’t need to worry for your yeast. However, you don’t want to overdose since it adds ionic content that may not benefit the beer.

Yooper - Thank you for the links. A lot closer to what I am looking for versus you’re wrong and and a troll. I wonder why they weren’t posted sooner during my rambling phase. I really am trying to keep learning and if something isn’t making sense I’m going to keep pushing until I get it figured out.

I still am missing one thing. How, and in mechanisms, chloroamines form chlorophenols. Can anyone help me answer this? Because if they don’t, then you really don’t need to worry about sulfites in the first place.

We are all here to learn (I learn every day), but we don't want to take away from the OP's question. If we want to discuss chlorophenols in great detail (or have a 'rambling phase') please start a new thread/question. Thanks!

 

[mabrungard]

I appreciate that Barada83 is a learned person. While I have a Masters in Environmental Engineering that included intense study of all things water and wastewater, I was quickly humbled decades ago when I tried to assert my knowledge without understanding the MORE complex chemistry of brewing. I was schooled on the subject through interactions such as this forum and I learned beyond my engineering training and experience. Not all the 'truths' from medicine and biology are likely to apply to brewing (or more correctly, there is more to this subject than you realize).

Regarding the degradation of bisulfite to sulfur dioxide, there are plenty of sources that attest to this phenomena. Sodium sulfite is a daughter product of sodium metabisulfite and it represents what is present in our water and wort solutions. This resource confirms that heating does drive off SO2: https://www.southernionics.com/pdf/pb/Sodium_Bisulfite_40.pdf

 

[RPh_Guy]

This resource confirms that heating does drive off SO2: https://www.southernionics.com/pdf/pb/Sodium_Bisulfite_40.pdf

This resource provides no data about how much SO2 is driven off. Are there any sources that do?

It's important to consider the pH. The average pH of the solution in that document is 4.0. In comparison, the fraction of sulfite species present in wort (pH 5.4) as volatile sulfur dioxide is more than 1 order of magnitude smaller.

The chemistry shows that over 99.97% of the sulfite in wort is ionized and therefore not volatile (using a pKa2 of 1.81).
The mechanism by which sulfite breaks down in wort is oxidation, not evaporation. For anyone using sulfite just for chlorine/ chloramine removal, any residual sulfite will oxidize to sulfate immediately upon mash-in by reaction with oxygen radicals.

This matches extensive low oxygen brewing experience, which provides ample anecdotal evidence that sulfite is not driven off during the boil, at least not entirely. I'm working on a reliable testing method so I can provide scientific data for this.

 

[barada83]

“The chemistry shows that over 99.97% of the sulfite in wort is ionized and therefore not volatile (using a pKa2 of 1.81).”

That’s exactly right. There’s a resource I posted a few posts previously discussing sulfites in wine making which is dealing with other a much more acidic environment in which the reaction equilibrium pushing the aqueous sulfites towards the less soluble hydrogen disulfide.

One of the more interesting ways to get rid of sulfites / sulfides described in the article Was to spray against the side of a vessel causing a better exchange condition for a dissolved gaseous compound to come out of solution. But with beer being way less acidic, it is also way more soluble in water. (There’s a telling chart that goes through the status of sulfite through the ph range).

Now, with reaction equilibrium and the availability of hydronium ions in the system, there WILL be Sulfur dioxide in the solution that can gas off. Just not much.

I don’t like being called a troll is all. Brewing is more complex than anyone realizes. Sometimes we all are wrong. Me included.

 

[dmaxweb]

I'm using a blend of county and RO water. Do I calculate the amount of potassium meta bisulfate needed based only on the amount of county water in the blend?

 

[dmtaylor]

I'm using a blend of county and RO water. Do I calculate the amount of potassium meta bisulfate needed based only on the amount of county water in the blend?

Yes