potassium metabisulfite (KMS) addition for bottle conditioning

[Sipina]

I've been recently reading and researching about the usage of KMS in the brewing process. I will be gradually implementing more steps that make sense for my system to reduce oxygen however the first thing I would like to try out is the addition of KMS when bottling. I will soon be bottling my next batch which is a bit more on the hoppy side.

My main concern is the conversion of KMS into H2S upon refermentation in the bottle. Supposedly the yeast can uptake the SO2 and convert it into H2S which will be perceived as strongly sulphuric in the end product. I've read quite a few posts on different places where people discuss and have read mixed experiences. Some report no issues while some reported the presence of H2S in the end product. I wish to avoid H2S at all costs in the end product.

I do not cold crash before bottling. I transfer my beer from PV to a bottling bucket where I add the sugar solution into which I would this time add the KMS powder. For transfering I have used an auto-siphon however I might use the pipe at the bottom of PV or even possibly bottle direct from the PV and add the sugary + KMS solution into bottles however this would mean implementing more than one new step and possibly make the picture of KMS effect less clear altough getting even less oxidation is of course desirable.

I would be more than happy to hear some of your thoughts and some tips&tricks regarding KMS usage and racking the liquids. CO2 purging is not an option the moment.

Happy brewing!

 

[Skeeter686]

I've been recently reading and researching about the usage of KMS in the brewing process. I will be gradually implementing more steps that make sense for my system to reduce oxygen however the first thing I would like to try out is the addition of KMS when bottling. I will soon be bottling my next batch which is a bit more on the hoppy side.

My main concern is the conversion of KMS into H2S upon refermentation in the bottle. Supposedly the yeast can uptake the SO2 and convert it into H2S which will be perceived as strongly sulphuric in the end product. I've read quite a few posts on different places where people discuss and have read mixed experiences. Some report no issues while some reported the presence of H2S in the end product. I wish to avoid H2S at all costs in the end product.

I do not cold crash before bottling. I transfer my beer from PV to a bottling bucket where I add the sugar solution into which I would this time add the KMS powder. For transfering I have used an auto-siphon however I might use the pipe at the bottom of PV or even possibly bottle direct from the PV and add the sugary + KMS solution into bottles however this would mean implementing more than one new step and possibly make the picture of KMS effect less clear altough getting even less oxidation is of course desirable.

I would be more than happy to hear some of your thoughts and some tips&tricks regarding KMS usage and racking the liquids. CO2 purging is not an option the moment.

Happy brewing!

I have successfully used potassium metabisulfite and ascorbic acid in the keg to mitigate oxidation of an IPA. However, when switching to a slightly different method for adding these, I somehow miscalculated the amount and the excessive metabisulfite did ruin the beer with sulfur aroma.

I have never used it when bottling, myself. I assume it should work, but I would advise you to be careful about ensuring that you're adding the appropriate amount to each bottle.

One other comment I'll add is that my wife uses potassium metabisulfite along with potassium sorbate to stabilize mead. I believe that the yeast are only suppressed in the presence of both of these chemicals, but you may want to confirm that potassium metabisulfite won't interfere with the yeast carbonating your beer.

 

[mashdar]

H2S flavor threshold is reportedly ~15ppb, whereas typical wine racking dose of SO2 is 10-50ppm.

If it can be converted (?), even low rates might be perceived? But I suspect it wouldn't be totally ruined; give it a try! (Probably max 50ppm SO2)

 

[BrewnWKopperKat]

For transfering I have used an auto-siphon however I might use the pipe at the bottom of PV or even possibly bottle direct from the PV and add the sugary + KMS solution into bottles however this would mean implementing more than one new step and possibly make the picture of KMS effect less clear altough getting even less oxidation is of course desirable.

With my most recent bottling process update, I did 'split batches' at bottling time. With 2.5 gal batches, there is enough wort for testing up to six different changes (e.g. three slurries and two bottle conditioning environments) at the same time.

 

[Snuffy]

Additives to think twice about​

1. Sulfites. Sulfites are a preservative many people are sensitive to that can severely aggravate asthma. Their use on fresh fruits and vegetables is banned in the United States, but sulfites are present in other foods. (Avoid products listing sulfur dioxide, potassium bisulfite, sodium bisulfite or sodium sulfite on the label.)

 

[Bassman2003]

As a low oxygen brewer, the use of KMB or SMB is usually confined to the mash and expended with oxygen before pitching the yeast. Yeast and raw KMB/SMB is thought to not be a good mix. I would not use these for bottling additions. Maybe ascorbic acid but that has mixed reviews as it may be an oxidizer in certain situations. Some experimentation with blind tastings and control observations would be fairly easy with bottling to really see what makes a positive impact.

 

[Maylar]

One other comment I'll add is that my wife uses potassium metabisulfite along with potassium sorbate to stabilize mead. I believe that the yeast are only suppressed in the presence of both of these chemicals, but you may want to confirm that potassium metabisulfite won't interfere with the yeast carbonating your beer.

Commercial yeasts are fairly tolerant of sulfites, but for bottle conditioning I would limit them to "1/2 dose", which is about 25 ppm.

For wine and mead, it's the sorbate that inhibits yeast growth. However, grapes carry Lactic Acid Bacteria (LAB) in nature, and that can metabolize sorbate into a nasty wine fault called geraniol which makes the wine smell like geranium flowers. The addition of sulfite prevents that from happening. I use it in my mead too.

 

[BrewnWKopperKat]

With regard to improving the bottle conditioning process (not re-packaging from kegs), recently there were some longer running topics/posts (some in Brewers Friend forums, but mostly over in AHA forums) where competition brewers mentioned how they went from uppers 30s to lower 40s by refining their bottle conditioning process.

In these discussions, I did not see consensus on the use of KMB, SMB, or ascorbic acid. Apparently, those using KMB/SMB found dose rates that were effective and didn't create off flavors.

In my 'split batch' bottling trials, I had some bottles that sugested that ascorbic acid - in combination with other items - made some difference. When I used ascorbic acid without those other items, it didn't help. I didn't include KMB/SMB in those trials - and I currently have no interest in using it during packaging.

 

[MaxStout]

I've had good luck with AA and SMB in my bottled beer, so I'll add a data point to this discussion, FWIW.

I had read about this a few years back on another site devoted to LODO, one I cannot link here, unfortunately. However, it's easy to find online.

The site mentioned using AA in conjunction with SMB, about 10ppm of each. They stated that AA alone could actually cause more oxidation, so you need to add the metabite. They also said to use SMB, not KMB, as potassium could be harmful to yeast.

I started adding 10ppm of the two to the bottling bucket, which comes out to about 0.2g of each for a 5 gallon batch. I weigh it to make sure I don't go over on this. I just dissolve it in the beaker of priming sugar solution.

I've done this the last couple dozen or so brews and I have noticed my bottled beer has a longer shelf life than before.

With the last few brews I've bumped up the dose to 20ppm each, with no effect on the yeast and no noticeable off-flavors.

 

[Bassman2003]

No doubt, sulfites work magic when it comes to oxygen. As long as they do not affect your flavor a little dose does a lot.

 

[Hoochin'Fool]

For my last 2 hoppy beers, I've done what MaxStout does: mixing up a priming solution, adding the ascorbic acid and k-meta to that, and then dumping it into the fermenter and giving it a gentle stir, then bottling directly from the fermenter's spigot. Still early, but it seems to be an improvement.

Haven't tried this with any of my stouts yet, but will for my next.

Also, if k-meta is bad for yeast health, it hasn't hurt my bottle carbonation (or flavor) any.

 

[dmtaylor]

You might get H2S. But it will disappear with age.