K-meta Shelf Life

[mainshipfred]

I've always wondered about the shelf life of K-meta powder. Everything I read says one year though it's also mentioned to throw it out after 3 years. My thoughts have always been if it's sealed what could go wrong with it. However this may not be the case. While recently adjusting the sulfites on my peach wine I had to add about 3 times the amount (using FermCalc) to get to the proper level of free SO2. I bought 5 lbs in September of 2020 but didn't open the package until June of last year so it's over a year old.

I'm going to order a lesser quantity and when it comes in I'm going to put measured amounts in 2 of the same wines and check the free SO2 just to check. I'm a little worried since I don't usually check the SO2 after putting in the recommended amounts and afraid I may have not me my desired levels in previously sulfited wines. The ones in bulk I can adjust I'm just concerned about the ones I bottled.

 

[winemaker81]

I found a technical spec sheet that said when stored at < 25 C and < 45% humidity, the shelf life is 6 months. If this is correct, I've been doing it wrong for decades. I know I've stored K-meta as long as 2 years and suffered no ill effects, which does not mean it didn't degrade during that time. It's entirely likely that good fortune smiled upon me.

Silly question -- are you sure the SO2 test is accurate, e.g., are the testing materials old?

Regarding all additives except bentonite, I tend to order what I expect to use in the next 6-12 months.

 

[mainshipfred]

I found a technical spec sheet that said when stored at < 25 C and < 45% humidity, the shelf life is 6 months. If this is correct, I've been doing it wrong for decades. I know I've stored K-meta as long as 2 years and suffered no ill effects, which does not mean it didn't degrade during that time. It's entirely likely that good fortune smiled upon me.

Silly question -- are you sure the SO2 test is accurate, e.g., are the testing materials old?

Regarding all additives except bentonite, I tend to order what I expect to use in the next 6-12 months.

I was using up my old reagents but when I saw this issue I tested it with the new ones and the results were the same. I also reset the meter and tested the electrodes on and everything read good so it has to be the K-meta. When the new stuff comes in I'll let you know the results. I have several wines to bottle but I don't want to do it until I figure out what the problem actually is. From what I read the additional powder doesn't hurt anything, it's just the guessing game of how much to add and the additional tests required.

 

[winemaker81]

I was using up my old reagents but when I saw this issue I tested it with the new ones and the results were the same.

I figured you took precautions, but best to ask the question.

What PPM are you targeting? I'm a dinosaur, I simply add 1/4 tsp K-meta per 5 gallons at each racking (post-fermentation) and at bottling. @NorCal's recent post about his testing indicates that the ancient rule-of-thumb actually works. But with fresh K-meta.

If the new batch proves out what your current results indicate (old K-meta is degraded badly), then dump the old stuff. It sucks dumping that much K-meta, but that will suck FAR less than losing wine.

I purchase in 8 oz bags, typically twice a year. Between NorCal and you, I'm a believer in the old rule AND buying fresh K-meta periodically.

May is 41 years of winemaking for me, and I'm still learning. Anyone who isn't learning has their eyes and ears closed.

 

[mainshipfred]

I figured you took precautions, but best to ask the question.

What PPM are you targeting? I'm a dinosaur, I simply add 1/4 tsp K-meta per 5 gallons at each racking (post-fermentation) and at bottling. @NorCal's recent post about his testing indicates that the ancient rule-of-thumb actually works. But with fresh K-meta.

If the new batch proves out what your current results indicate (old K-meta is degraded badly), then dump the old stuff. It sucks dumping that much K-meta, but that will suck FAR less than losing wine.

I purchase in 8 oz bags, typically twice a year. Between NorCal and you, I'm a believer in the old rule AND buying fresh K-meta periodically.

May is 41 years of winemaking for me, and I'm still learning. Anyone who isn't learning has their eyes and ears closed.

The pH was 3.65 so I was trying to get it to 60 ppm. I had 4 five gallon carboys each with a different yeast that I wanted to homogenize so on Friday I racked then filtered them with a 1 micron. On Saturday morning they were filtered with a .5 into a brute and back sweetened then back to the carboys. By this time it was down to 7 ppm. Fermcalc said 1.9 grams was needed to get to 60 ppm but it barely got to 20 ppm. Turns out I needed 5+ grams, can't remember exactly what it turned out to.

 

[balatonwine]

back sweetened

Doing that might change the chemistry.

I have found that wines with residual sugar can change the chemistry compared to a dry wine. And testing after adding Kmeta I have to add more to a sweet wine.

Dry wines seem to fit a more stable profile.

At least that is my experience. Experience can vary.

For what it is worth.

 

[mainshipfred]

Doing that might change the chemistry.

I have found that wines with residual sugar can change the chemistry compared to a dry wine. And testing after adding Kmeta I have to add more to a sweet wine.

Dry wines seem to fit a more stable profile.

At least that is my experience. Experience can vary.

For what it is worth.

Wow! that is very interesting. Not sure I would have ever considered that. Fruit wines, which I make very little of, is the only ones I back sweeten.

Thank you!

 

[stickman]

The last few sulfite products I purchased (Oenosteryl tablets, Vason k-meta powder) had a dated shelf life of 2 years if unopened. When I buy the powder, I get the 1kg product in its original bag and immediately repackage into several brown glass bottles with metalized cap liner. This way the unopened bottles should keep for at least 2 years, probably longer, as most of the degradation is due to repeated exposure to moisture, oxygen, and warm storage temperature etc.

 

[heatherd]

I'm glad you mentioned this @mainshipfred and @winemaker81. I stabilize after fermentation with k-meta, then do scheduled k-meta additions every three to four months of 1/4tsp per five gallons during bulk-aging, as read here that a couple of folks have tested theirs and found to be effective. I tend not to test because I haven't felt I needed to. I just ordered new k-meta and will chuck the old stuff.

 

[mainshipfred]

The last few sulfite products I purchased (Oenosteryl tablets, Vason k-meta powder) had a dated shelf life of 2 years if unopened. When I buy the powder, I get the 1kg product in its original bag and immediately repackage into several brown glass bottles with metalized cap liner. This way the unopened bottles should keep for at least 2 years, probably longer, as most of the degradation is due to repeated exposure to moisture, oxygen, and warm storage temperature etc.

A kg seems like a more reasonable amount. Mine came in a metal looking zip lock bag and was kept in my cooler at 57*. When I close it I always squeeze as much air out as possible. It was only opened once to fill my smaller container. When the issue first came up I took a small amount directly from the bag and the results were the same. I'm still going to get new but I think @balatonwine could possible have hit it on the head.

 

[Rice_Guy]

The risk to metabisulphite is that moisture allows the sulphite to ionize and if enough water is present it can allow free SO2 to be generated. There is little risk in a storage area that has low humidity. If you have significant free SO you should be able to look in your work area and see significant rust on steel items and you should be gagging in a closed area with it. Did your bag/ jar come with an EPA warning? ,,, ?does your old aunt with asthma gag when visiting you house? ? ,, probably not,
What percentage of the free SO2 do you think is released? It is toxic,, some folks have reactions to it,, you should be able to smell it if it is at 100ppm in air,, it is very reactive on metals,, it is considered safe enough to allow in non-protected home environments,, . . . Assuming 0.0001% has been released my scale isn’t accurate enough to measure the lost gas.

Consider storing your meta in glass, ,,, your goal is to exclude fresh air with fresh humidity that can react. If you want to be very picky consider adding a desiccant to the container.
I treat meta as if it is a ambient shelf stable chemical. Having been in meetings with our director of QA, a one year feels like a CYA. ,,, or a marketing tool to get you to toss and buy new.

 

[mainshipfred]

There are probably more variables than I'm aware of but it seems the back sweetening could have something to do with it. I just did a before and after test with the old Kmeta to a dry red wine. The starting free SO2 was 25 ppm, when adding the FermCalc recommended amount to get it to 50 ppm it tested at 46 ppm. I've heard some is immediately bound so that could play a role in the finish number. Even though it is probably degrading 25 to 46 with a target 50 is a lot better than 7-20 with a target of 60. BTW it was packaged 6-19 but not opened until 6-21.

 

[Rice_Guy]

there are several places where error is built into the measurement as the pH that was used in the Fermcalc formula and the minimum ppm in one drop of titrant and if you used an analytical balance for weighing and the chemicals in your free SO2 test. You seem to have accomplished target dosage within expected error.

There are probably more variables than I'm aware of but it seems the back sweetening could have something to do with it. I just did a before and after test with the old Kmeta to a dry red wine. The starting free SO2 was 25 ppm, when adding the FermCalc recommended amount to get it to 50 ppm it tested at 46 ppm. I've heard some is immediately bound so that could play a role in the finish number. Even though it is probably degrading 25 to 46 with a target 50 is a lot better than 7-20 with a target of 60. BTW it was packaged 6-19 but not opened until 6-21.

As far as bound sulphite. The base level / floor on binding is ten ppm. If you were starting below ten that factor would start being important.

 

[mainshipfred]

As far as bound sulphite. The base level / floor on binding is ten ppm. If you were starting below ten that factor would start being important.
[/QUOTE]

I'm not sure I'm understanding this. Would you mind elaborating?

 

[crushday]

I've always wondered about the shelf life of K-meta powder.

I’ve had this question. I use powder during winemaking and for sanitation solution for equipment. For storage, however, I use Inodose tablets. There is no expiration date stamped on the box or any of the blister packs. I looked on the Scott Labs website and there’s no mention of the tablets expiring, only a warning to use the tablet if the blister pack is opened.

Additionally, I can’t find anywhere that Campden tablets have an expiration date either.

Even after all the afore dialog, there’s still a question to be answered…

 

[mainshipfred]

I don't like beating a dead horse but this Kmeta thing has got me puzzled. I just received my new Kmeta and wanted to do something fast. Filled two 5 gallon carboys with tap water and sulfited it to 15 ppm because my meter won't read below a certain number. Then added 1.2 grams of the old and new which was supposed to get it to 55 ppm.

After testing the old came in at 48 ppm and the new 46 ppm. Now I only did one test each so it's not good lab protocol and there is a slight margin for error but I think it is close enough to see that the old is still good.

If you see any holes in my findings please let me know. BTW, this is the first time I ever saw a color change in a titration and it was immediate.

 

[BarrelMonkey]

After testing the old came in at 48 ppm and the new 46 ppm. Now I only did one test each so it's not good lab protocol and there is a slight margin for error but I think it is close enough to see that the old is still good.

What method do you use to measure SO2?

 

[mainshipfred]

What method do you use to measure SO2?

I have the Vinmetrica 300.

 

[BarrelMonkey]

I have the Vinmetrica 300.

So Ripper method? I was a bit confused by the color change comment - I have run Rippers and the color change (colorless to purple from the iodine-starch reaction) comes immediately if there is zero SO2 (since there is nothing to react with iodine apart from the starch indicator). If there's a lot of SO2, then you have to add a lot of the iodine titrant to react with all the SO2 before you see a long-lasting color change. But maybe the Vinmetrica method is different?

Regardless, ripper method should be pretty reliable on a sample in water, and your new/old samples look identical. I agree with your conclusion and @Rice_Guy's earlier comment that K-meta should be pretty stable at room temperature as long as it's dry and in a sealed container.

 

[BarrelMonkey]

For storage, however, I use Inodose tablets. There is no expiration date stamped on the box or any of the blister packs.

If you look on the top of the box there are some numbers. I think that the first 6 digit number is the manufacture date and the last 4 digit number the expiration date. For example, on my box the first number is 210621 (21st Jun '21 in European/English format) and the last number is 0624 (June '24). So I think your Inodose tabs should be good for at least a few years