K-meta/Citric solution

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It has been my understanding K-meta is most affective at a pH of 2.0. I started with 2 grams of K-meta and 4 grams of citric and added citric until I got to a pH of +/-2.0.
It turns out one part K-meta to 4 parts citric gets you to around 2.0. I've been using 2:3 for years for no scientific reason.

I ran out of titrant solution so I couldn't test for ppm's but I can say 1:4 grams in 100ml of water is over 200 ppm.
 
It has been my understanding K-meta is most affective at a pH of 2.0. I started with 2 grams of K-meta and 4 grams of citric and added citric until I got to a pH of +/-2.0.
It turns out one part K-meta to 4 parts citric gets you to around 2.0. I've been using 2:3 for years for no scientific reason.

I ran out of titrant solution so I couldn't test for ppm's but I can say 1:4 grams in 100ml of water is over 200 ppm.
This seems really high to me...

1g K-meta in 100mL is 6000ppm (handy calculator here).

My recipe for sanitizing solution is 6g K-meta + 1lb (~450g) tartaric acid in 8 US gal/30L water, which yields 0.1M tartaric acid pH ~2 and ~100ppm SO2. Citric acid is a bit weaker (but much cheaper!) than tartaric, so maybe use, say 900g (30g/L), ~0.15M citric acid.
 
I've been using 2 to 3 Tbsp K-meta + 1 Tbsp acid in 1 US gallon water, because that was the recipe I was given. That's WAY off, ratio-wise.
And according to Daniel Pambianchi (Modern Home Winemaking), 10g sulfite and up to 3g citric acid in 1L water. That's about 600ppm and pH ~2.5.

I think some of the disconnect is the intended application. If you're just going to do a quick spray/soak before using equipment, the higher dose might be appropriate. For longer term soaking/sanitary storage, perhaps the lower dose.
 
Recently read an article and I started using 3 tbsp citric acid per gallon of warm water to help clean racking hoses and other difficult to clean parts. Then following with 3 tbsp/gallon kmeta for sanitizing.

I also recently cracked my first carboy using this method. The temperature differential was very minimal but under a vaccum, the carboy is much more susceptible to damage. Hindsight is obvious now.

I blow compressed air through the hoses to remove residual sanitizer.

Might be overkill but I'm trying to make my hoses last as long as possible.
 
I blow compressed air through the hoses to remove residual sanitizer.

Might be overkill but I'm trying to make my hoses last as long as possible.
I rinse everything in water after use, including racking hot water through tubing and canes, then hang hoses to dry. Prior to next usage, everything is sanitized.
 
The chemistry course answer is that there is a property called pKa where half of the molecule is disassociated as free SO2 and half is in a complex. For the bisulphite ion this is at pH 1.8,, Other ions will have different points where this reversible reaction occurres.

The essence is that the lower we can push the pH the higher the percentage of free SO2 will be in the liquid. We can also increase the ppm of free SO2 by increasing the concentration of metabisulphite > bisulphite ion in the solution.

pH 2 is not a magic number.
 
I used just K-meta for decades, adding acid only in the last 2 or 3 years. IME, plain 'ole K-meta works fine for sanitizing, but adding acid makes it better.

Something to consider is if "better" is important.

From my research, simply cleaning all equipment well removes the vast majority of all contaminants, including microbial life. Recall the "sanitizing" is the removal of microbial life to below a threshold where it is not a threat to the wine. We are not sterilizing, e.g., the removal of all microbial life, which is not necessary for winemaking, nor is it practical.

If a common formulation for K-meta solution (e.g., 2 Tbsp K-meta, 1 Tbsp acid, 1 US gallon water) is fully effective, is there any value in making a better solution?

This is a good discussion. While I'm unlikely to change my K-meta solution formulation, it helps me understand the chemistry behind it. A lot of folks are using my above the formulation I mentioned above, and this formulation probably developed because it works. Now we know why it works.

As I'm fond of saying, understanding why is more important that what or how.


From my research, there isn't necessarily a need to sanitize with K-meta if all equipment is properly cleaned. Yet I do it. Why?
Because after cleaning, my equipment is probably sanitized, but after cleaning + K-meta, I know it's sanitized. If nothing else, it gives me peace of mind and eliminates a potential problem.
 
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And while we're on the subject - don't store your acidified K-meta solution in a spray bottle. It's fine to use temporarily (and convenient for sanitizing many winemaking items), but if you leave it in there it will erode the mechanism.

I have not found this to be an issue. I have twobottles of Kmeta solution I purchased probably 5-6 years ago and those were replacements for ones that were about that same age. I don't recall exactly why I replaced them, they still mostly worked, as I recall, but I have slept a bunch of times since then.
 
I have not found this to be an issue. I have twobottles of Kmeta solution I purchased probably 5-6 years ago and those were replacements for ones that were about that same age. I don't recall exactly why I replaced them, they still mostly worked, as I recall, but I have slept a bunch of times since then.
You must buy much nicer spray bottles than me! 😄

(Or it may again depend on the strength... for a quick spray I use a few % w/v, which will be 10000-30000ppm. Much more than my 'soaking' sanitation solution...)
 
I have not found this to be an issue. I have twobottles of Kmeta solution I purchased probably 5-6 years ago and those were replacements for ones that were about that same age. I don't recall exactly why I replaced them, they still mostly worked, as I recall, but I have slept a bunch of times since then.
It depends on the mechanism. Yard pump sprayers typically have metal parts, but those rated for bleach do not. I assume your spray bottle has no metal parts that touch the liquid, or are a metal unaffected by sulfite (assuming such a thing exists).
 
I've had major corrosion when storing Kmeta sanitizing solution in a canning jar with a canning lid. Keep it away from metal!

I found a chemical resistant spray bottle that I use for my Kmeta solution, and another for StarSan. They work great!
 
I doubt these are particularly nice, just the cheapest ones I walked past in Lowes one day and they work great, around me, they cost about $4 US each. If I get even 3 or 4 years out of one, I figure I got a good deal.
Those are all plastic. In this case, cheaper quality is actually good!
 
I've been using 2 to 3 Tbsp K-meta + 1 Tbsp acid in 1 US gallon water, because that was the recipe I was given. That's WAY off, ratio-wise.
What type of acid specifically do you use? Acid blend? I’ve been using StarSan or a kmeta solution of 2.5 tbls per gallon. So far so good.
 
Citric acid is not recommended because of the citric acid cycle in bacteria. I used tartaric for KMS solutions for sprays and short-term barrel storage.
On the other hand, you can use citric acid additions and MLF to create diacetyl if you like buttery wines.
 
If you mix sanitizer with tap water from a carbonate rock (pH 7 to 8) then better is important. If you have tap which is extremely soft as from the Louisiana bayou (pH 5 to 6) I could say who cares? Likewise if mixing up with distilled water and 0.1 gram of any acid.
, but adding acid makes it better. . . Something to consider is if "better" is important.
Another consideration is organic load. Bisulphite ionic form is useless ao oxidizing organics (bacteria/ fungi). Low pH is a kill treatment for many families of bacteria and fungi. ,,, ie there are two sanitizing principals.
canned foods are treated to kill nine log cycles of microorganisms. ,,, Washing with hot water and soap can remove six to seven log cycles of population. If we have done a good job washing it doesn’t matter, >>>> how sloppy are we?
 
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