Replacing Potassium Metabisulfite

[Huba Huba]

I don't have a way to measure free sulfite but try to remember to replace my K Meta every 6 months. I recently bought a new LD Carlson 2 oz package, Looking on the internet the consensus seems to be that K Meta should be good for 12-18 months from manufacture. There is no date, "manufacture" or "best by" or even a lot number on the package, or on any of the old packages I still have. I always thought that it was good for up to 6-12 months after opened. As far as I know any package I buy could have been sitting on a shelf for 18 months.
How do you know if it is good?

 

[winemaker81]

I make enough wine that I typically buy an 8 oz bag every 12-18 months, depending on usage. However, I've used K-meta that was 2 years old.

Make up a K-meta sanitizing solution, with 2 to 3 Tbsp K-meta in 1 US gallon / 4 liters water with optionally 1 Tbsp acid. Sniff it VERY gently. If it burns your sinuses, it's plenty good.

I'm paranoid about sorbate, as when sorbate ages out, the risk is a batch of mini-Mount Vesuvius, e.g., refermentation in the bottle. If the K-meta reeks, it's still at least somewhat effective so I'm a lot less concerned.

 

[BarrelMonkey]

I make enough wine that I typically buy an 8 oz bag every 12-18 months, depending on usage. However, I've used K-meta that was 2 years old.

Make up a K-meta sanitizing solution, with 2 to 3 Tbsp K-meta in 1 US gallon / 4 liters water with optionally 1 Tbsp acid. Sniff it VERY gently. If it burns your sinuses, it's plenty good.

Sniff test is good. I would also add that if it's stuck together in big clumps it's also time for a new batch - you want it to be dry and powdery so that it can be accurately measured and dissolves fully before adding to your wine.

 

[Rice_Guy]

As a chem lab person, if the potassium metabisulphite is dry it will have years of shelf life. On chemicals I am concerned about I store them in glass. Meta reacts with metal so a plastic lid or at least a Saran liner should be used.
I make a sanitizer with meta. My test for effectiveness is carefully waft some headspace at my noise. It should burn if free SO2 present. On wines if I don’t test, I assume country wines are zero ppm and reds are about 10ppm.

 

[Huba Huba]

OK, sounds like replacing my K Meta every 6 months should keep me out of trouble. I did not know that I needed to do the same with K sorbate, I will start replacing that every 6 months also.
Do you worry about chems included in kits? I have bought a couple of RJS Dessert wine kits recently on sale/closeout and will not make them for a couple of months. Removed/refrigerated the yeast, should I just discard the Meta/KSorb that came with the kits and use my "fresher" ones.

 

[winemaker81]

OK, sounds like replacing my K Meta every 6 months should keep me out of trouble. I did not know that I needed to do the same with K sorbate, I will start replacing that every 6 months also.
Do you worry about chems included in kits? I have bought a couple of RJS Dessert wine kits recently on sale/closeout and will not make them for a couple of months. Removed/refrigerated the yeast, should I just discard the Meta/KSorb that came with the kits and use my "fresher" ones.

IME you don't need to replace K-meta or sorbate every 6 months.

Vendor docs indicate sorbate, in correct storage conditions, is good for 2+ years. Since mine is in a drawer in a clear plastic bag, I keep mine 12-15 months, which allows for time in the warehouse and on the LHBS' shelf. I have never had a problem doing this.

My habit is to date EVERYTHING when I buy it.

 

[Rice_Guy]

OK, sounds like replacing my K Meta every 6 months should keep me out of trouble. I did not know that I needed to do the same with K sorbate, I will start replacing that every 6 months also.
Do you worry about chems included in kits? I have bought a couple of RJS Dessert wine kits recently on sale/closeout and will not make them for a couple of months. Removed/refrigerated the yeast, should I just discard the Meta/KSorb that came with the kits and use my "fresher" ones.

This is excessive, , unless these chemicals get wet. They are shelf stable with dry normal warehouse storage.
K metabisulphite has years of life in the original plastic bag. On a percentage free SO2 calculation the pH of your juice / wine will be more important than the years in a plastic bag. The percentage error on how much we fill onto the plastic bag is more than the loss over five years. Sorbate is more reactive to humidity but again has years of life when in normal US storage. If I was in the Amazon with rain every day I could chart the water vapor transmission rate of the plastic bag and then have some concern. IF humidity was a serious issue for the manufacturer we would package those chemicals in aluminized film like seasoning packets in ramen noodles and flavored rice mixes. These films are rated to have vapor transmission rates like glass bottles and as Barrel said if the chemical has formed a lump it has degraded.
Yeast packets are designed for over kill, they out compete any wild yeast you might have in your equipment. On a practical basis if I have one live yeast cell out of the millions in a yeast packet it will ferment, but with a slow start up.

Some of the company’s best by code dates were chosen because the packaging starts to fade under the fluorescent lights in a store. The feeling was that it would be hard to sell.

 

[winemaker81]

@Rice_Guy, do you believe my "toss sorbate after 12-15 months" is too paranoid? I won't be offended if you do, as I respect your opinions regarding the chemical side of winemaking.

I'm a touch, see, and feel guy. With K-meta I can dissolve a small amount in water and gently sniff it. If it makes me cough my lungs out, I know it's good.

With sorbate, the only way I'll know that it's degraded too much is by having cases of wine blowing their corks. I had that happen once (caught it early, so only pushed corks partially out), and had to rebottle 2 cases of wine. From my POV it's cheaper and easier to buy small packages of sorbate (when I need it), and bin the small amount that remains after 12 to 15 months, than it is to unbottle 2+ cases of wine and later rebottle them.

As mentioned above, I looked at vendor docs, consider that the package spent an unknown amount of time in the warehouse and on the LHBS' shelf, and consider my less than stellar storage conditions.

You mentioned yeast -- that's a good reason to make a starter. My package of Avante will be used in the 5th ferment next fall. I'll make starters, and will know within 10-30 minutes if my yeast is viable. [Touch, see, & feel!]

All that said, my practice is to buy additives in quantities that will be used up in a year or so, then buy more at the time it's needed. This eliminates the question, "is it too old?". [Any powders that clump are immediately binned.]

 

[Venatorscribe]

OK, sounds like replacing my K Meta every 6 months should keep me out of trouble. I did not know that I needed to do the same with K sorbate, I will start replacing that every 6 months also.
Do you worry about chems included in kits? I have bought a couple of RJS Dessert wine kits recently on sale/closeout and will not make them for a couple of months. Removed/refrigerated the yeast, should I just discard the Meta/KSorb that came with the kits and use my "fresher" ones.

Re kit chemicals - I normally toss them. And sachets of finning agents I just blend into my compost bin or direct to garden soil. I stopped using sorbate some time back. I just hold wine in 10 lt food grade plastic carboys and leave for a good twelve months before bottling.

 

[Rice_Guy]

@Rice_Guy, do you believe my "toss sorbate after 12-15 months" is too paranoid? I won't be offended if you do, as I respect your opinions regarding the chemical side of winemaking.

There are two ways to measure the shelf life of potassium sorbate. 1) as a dry granular ingredient which needs to be dissolved into a water based liquid ie as produced waiting for incorporation into a food / beverage / cosmetic. A specification will give two to three years of shelf life. This is defined as lab analysis will still detect {? 99% ?} active ingredient. and 2) as something which is incorporated into a water based food, ie in final usage. Some forms as a 50% solution which can be poured from a 5 gallon pail will guarantee six months. Other references as using it as a preservative in cider will state one to a few months effectiveness. Sorbic acid is readily oxidized! As with all winery processes minimize the air in contact with the wine. Minimize iron, copper etc as normal to protect wine shelf life.
_________________________________________________
1) As copied from a supplier material data sheet / dry flowable powder:
Celanese; The finished products are stored at temperature and humidity monitored warehouse under GMP conditions (FSSC-certified). Removal from storage takes place according to the principle of first in first out (FIFO).
Transport and dispatch are carried out exclusively by authorized haulage contractors and distribution companies. The regulations governing the dispatch of food are observed.
During the storage of our products the following requirements must be fulfilled:
• Ambient temperature: max 30°C
• Dry conditions (max 65 % relative humidity)
• Protection from direct sunlight.
Sorbates are stored under these conditions in the unopened, originally sealed packaging unit, the shelf life is 3 years from date of manufacturing
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2) As analyzed in research on finished products / wet systems:
Sorbates PH
Sorbates are the more effective preservative against a wider spectrum of food spoilage microorganisms than benzoates or propionates When used at common pH levels of mildly acidic foods (pH 5.5 – 6.0).
Sorbates’ effectiveness increases with greater acidity (lower pH). Above pH 4.0, sorbates are more effective than sodium benzoate or sodium/calcium propionate.
At pH 2.5 – 3.0, sorbates are still somewhat more effective than sodium benzoate as a yeast and mold inhibitor, and more than twice as potent as propionates.
Sorbates are at their optimum effectiveness when used below pH 6.0. However they can function up to pH 6.5, but are relatively ineffective at pH 7.0 and above.

4.1 Potassium sorbate reaction in food​

It is known that the stability of potasium sorbate in foodstuffs is influenced by so many factors such as pH ratio and water activity, temperature, food combination, metal ions, packaging and presence of other food additives. The sorbate is relatively unstable and degrades in aqueous model of food systems and 35% of it losses after three months of storage at 30 °C and in foods with intermediate moisture, less than 25% after 40 days remains at 35 °C. The sorbate reacts with other groups in food products such as as carboxyl group and forms conjugates with them through double bonds. Thus, by degradation and polymerization of the sorbate via oxidating agents at the conjugated double bonds (CDB), the peroxides and degradated products such as carbonyl compounds including malondialdehyde, croton-aldehyde, and fumaraldehydic acid (FA) are generated. It has been shown that sorbate in food products can react with the secondary amines, ascorbic acid and ferrous salts and form different adducts at high temperatures, which in turn leads to the food browning (Ferrand, Marc, Fritsch, Cassand, & de Saint Blanquat, 2000; Thakur, Singh, & Arya, 1994). But the potent reactivity of sorbate in the presence of iron salts such as gluconate, citrate, and ferric

 

[winemaker81]

Thanks for posting. I read through the info twice, and scarily enough, I think I understand it.

• Ambient temperature: max 30°C / 86 F
• Dry conditions (max 65 % relative humidity)
• Protection from direct sunlight.
Sorbates are stored under these conditions in the unopened, originally sealed packaging unit, the shelf life is 3 years from date of manufacturing

My takeaway is that storage conditions are key.

Temperature. My cellar typically ranges from 57 F to 74 F (14 C to 23 C) around the year, so it's within storage parameters. Anyone storing the product in higher heat conditions needs to be concerned, e.g., my garage in the summer resembles the surface of Mercury.​

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Humidity. We have a dehumidifier which keeps the humidity below 50%, but when it gets full of water (and stops working), at certain times of year the humidity can spike to 75%, which is a problem. In the main part of the house, the humidity is probably fine. If I stored things in my garage, I'd get a lot less shelf life, as humidity in Raleigh spikes as high as 80% in the summer.​

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Sunlight. All my additives are kept in a drawer, so they're all protected from sunlight, so that's not a problem.​

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Packaging. All my additives are in plastic ziplock bags, which are far from "original packaging", but better than "wrapped loosely in a tissue". I press air out of packages when resealing them, but the plastic is not the greatest barrier.​

I have adjusted my estimate so I will keep sorbate for up to 18 months from date of acquisition. This is my risk tolerance, and others may feel differently.

A 1 oz bag of sorbate is $2.40 USD at my LHBS. Corks, capsules, and labels for 19 liters of wine are 4 times that, not including labor to address refermentation in the bottle. So for me it makes sense to buy when needed, and not worry about binning whatever remains 18 months later.

Now ... I feel the need to go through my drawer and investigate the shelf life of all my additives. I know I have things like calcium carbonate that are at least 5 years old -- that particular one may be fine, but others may not.

 

[Rice_Guy]

If you step back to post 4, as a lab person who used chemicals, the lab had a bell jar for keeping things that are hygroscopic dry. My home environment has recycled cheese dip glass where I put things that I want to keep out of ambient humidity. If I was in Houston or Miami I would also collect the silica gel packets that get added to some tools and food and regenerate them, then insert in the jar. Standard lab regeneration was a 150C electric oven at least an hour. (ex a toaster oven) (Lab grade has a pink to blue indicator) Different ingredients have assorted potential to suck moisture out of the air. ex Fermaid O has a lot of sugars and salts so it will cake, and when I get new Fermaid it automatically goes into a jar. Practically speaking I have found it convenient for shelf space so all bag materials go into tall containers. Yes , like you, there is a date on acid blend.

One has to react every chemical separately. ex the formaldehyde reagent in a Vinmetrica YAN kit will crystallize forming large white flakes if at 50F / 10C or lower like a refrigerator at the web based supplier.