Is it better to age before or after stabilizing?

[NeverDie]

Those automated SO2 testers are expensive.

One of them is around $300: https://www.thebeveragepeople.com/products/testing/vinmetrica-sc-100a-sulfite-tester.html

Well, I guess in-for-an-inch eventually becomes in-for-a-mile. Is this Vinmetrica the best that there is, or is there anything faster/easier or more automated than the SC100A?

 

[RPh_Guy]

Unfortunately, it's not as easy to avoid as that, though. According to the second article that loveofrose linked to, you also need to compensate for any other kind of binding that might happen too.

I've generally used wine yeast, so I'm assuming the yeast produced some marginal amount of SO2 and used up all the binding sites.

I agree it's not the best, but it's been working for me so far (my ciders are retaining fresh fruit character). I'm not really focused on wine making and testing SO2 seems like a pain in the ass, so I'll only do that if I find that I can't prevent off-flavors/oxidation using a minimalist approach.
Just my philosophy.

 

[bob1852]

One of them is around $300: https://www.thebeveragepeople.com/products/testing/vinmetrica-sc-100a-sulfite-tester.html

Well, I guess in-for-an-inch eventually becomes in-for-a-mile. Is this Vinmetrica the best that there is, or is there anything faster/easier or more automated than the SC100A?

If you're going to get that, might as well just get the 300 and be able to measure pH and TA as well as SO2...

 

[Maylar]

One of them is around $300: https://www.thebeveragepeople.com/products/testing/vinmetrica-sc-100a-sulfite-tester.html

Well, I guess in-for-an-inch eventually becomes in-for-a-mile. Is this Vinmetrica the best that there is, or is there anything faster/easier or more automated than the SC100A?

I think that one is the industry standard. I haven't been able to justify it. I bought the titration kit and haven't even used that yet. I've been using the old "50 ppm" 1/4 tsp K-Meta or 1 Campden per gallon and winging it. So far nothing has grown in any of my brews and I haven't had geraniums in a bottle, so I guess it's working.

 

[NeverDie]

It occurs to me that an overly simplistic way (perhaps not the optimal way) to approach this would be from the get-go to simply add the maximum about of potassium metabisulfite that can't be tasted--which would be how much exactly? That might give enough headroom to cover a multitude of sins, and who really cares if it's more than the minimum needed? Apparently it's just the total amount of SO2 added that's what you taste, not the free SO2 per se.

This way, testing wouldn't matter or be needed, because you've already added the maximum amount possible without ruining the taste. Aside from possible allergies, is there any downside to this brute force approach?

 

[bob1852]

Aside from possible allergies, is there any downside to this brute force approach?

Yes,

Free SO2 continues to be lost over time (dissipation and/or binding), so you don't know when, and how much, you need to add to optimize the needed amount.

As mentioned, you can estimate by using some of the old wine techniques (adding 50ppm at every other racking or every few months), but without accurate measurement, you'll never know if the free SO2 is at the optimal amount.

 

[RPh_Guy]

Off flavor occurs from molecular SO2 over ~ 1.0-1.2 ppm.

 

[NeverDie]

Off flavor occurs from molecular SO2 over ~ 1.0-1.2 ppm.

I don't know how to interpret that. How many grams/gallon of potassium metabisulfite does that translate into? Regardless, it would be nice to know the ceiling on the potassium metabisulfite additions.

 

[NeverDie]

Even the SC100A is a bit more involved than what I'd prefer. In contrast, it looks as though the Titrets are definitely the easiest and fastest way to test:


Maybe 30 seconds and then done. Virtually no setup or cleanup. I like that.

Just as the best camera is the one I have with me, the best SO2 test is the one that I'm willing to actually use.

For mead, has anyone compared the results of a Titrets with one of the more accurate methods? At least for a traditional mead that's clear amber, color won't be a problem.

Note: The guy in the video forgot to check for pH to determine how much SO2 he should have. Although he seems happy at 30ppm, if it's plus or minus 30ppm, he might well have zero! If 30ppm is, in fact, the right target amount, it seems to me that he should have added another 30ppm SO2 just to be sure.

 

[RPh_Guy]

For how frequently sulfite is used, there's a surprising lack of information available about how to use it. I think that's why most of us just wing it.

I'll try to explain what I know.

First, consider that sulfite products have a shelf life and degrade over time, especially with more oxygen exposure, so you might not be adding as much as you think you're adding.

To complicate matters, also remember that yeast produce sulfite during fermentation, varying by strain and possibly other variables. For example some wine strains allegedly may finish with up to 30ppm of sulfite in the wine.

Then, when you add metabisulfite to a liquid it reacts with oxygen. 1ppm dissolved oxygen (DO) neutralizes (oxidizes to sulfate) approximately 5ppm of the metabisulfite. If you aerated the heck out of it, it may contain up to 8ppm DO, neutralizing about 40ppm of the metabisulfite pretty much immediately.

After that, some of the resulting sulfite binds to various organic compounds (e.g. aldehydes) in the wine/must. Exactly how much binds is impossible to predict; I see figures ranging from 30-70%. (Why that's expressed as a percentage doesn't seem to make sense given that there's a finite amount of binding sites, so I don't even trust those widely variable numbers to be accurate.)
I hypothesize that binding capacity in wine is negligible because of sulfite produced during fermentation, but I have no data to support that.

Any remaining (unbound) sulfite is considered "free SO2", which is supposedly what protects the wine from oxidation since it's available to react with oxygen.
The bound sulfite may also be helping prevent oxidation to some degree.

In acidic aqueous media (e.g. wine), sulfite exists in equilibrium with molecular SO2. The percentage of molecular SO2 depends on the pH. You posted the chart above, I use a sulfite calculator.

Molecular SO2 is responsible for anti-microbial activity and supposedly is also what can cause off-flavor/aroma in the concentration I mentioned. Burnt match.
Allegedly 0.4ppm molecular SO2 starts to significantly inhibit bacteria/wild yeast and 0.8ppm greatly inhibits or kills the wild microbes and can start to affect Sacc. Sulfite tolerance varies by species and strain.

To know how much metabisulfite can be safely added to stabilize, you need to either know or assume that none of it will bind, or pick an arbitrary amount. Then after measuring pH you can calculate how much metabisulfite is needed to hit the target molecular SO2.
Edit: Of course, you can measure the free sulfite to a variable degree of accuracy and then calculate how much of that is molecular SO2.

To further complicate matters, bottling and aging both introduced oxygen, which will lower the amount of free sulfite.

Also FYI potassium and sodium metabisulfite are not interchangable since they provide different levels of sulfite by weight.
Campden is designed to provide 50ppm total sulfite at a rate of 1 tab per imperial gallon, or about 65ppm for 1 tab per US gallon.

Welcome to the crazy mixed up world of sulfite.

 

[NeverDie]

Is molecular SO2 any easier/faster to measure than free SO2? If so, maybe we can simplify this by relying on opti-white to handle anti-oxidation. After all, that seems to be job #1 for opti-white. Then we can ignore free SO2 and just worry about molecular SO2, if that's the part that kills the wild microbes.

 

[RPh_Guy]

To my knowledge only free sulfite can be measured.

 

[NeverDie]

I picked up a Titrets kit at my local homebrew store. If I add the SO2 just prior to bottling for the purpose of aging, how long do I need to wait before testing free SO2 levels? i.e. if there is binding after the SO2 addition which then needs to be compensated for by a calculated, further addition, does that binding happen instantly, in hours, in days, or longer?

 

[Maylar]

I think it's "free" right after you add it. Quantity based on pH, per those charts. Gotta break out the calculator and do a before/after test to verify I guess. Haven't got there yet, still using the old "50 ppm every other racking" trick. But I will give it a go next bottling session.

 

[NeverDie]

I dosed a mead to 150ppm free SO2, and, unfortunately, the SO2 can be tasted (not a good flavor, either). Therefore, whatever the taste threshhold is, it's something lower than 150ppm.

So, at present, the prognosis doesn't look good for the brute force method of SO2 dosing.

 

[Maylar]

Ick. I tend to be on the light side when I add sulfite. Like I'll use only a half tablet when I keg.

 

[NeverDie]

Ick. I tend to be on the light side when I add sulfite. Like I'll use only a half tablet when I keg.

Why?

 

[Maylar]

Why?

I don't want to taste it, and I don't know the threshold for that, as you mentioned. I submitted a cider to a comp once that was judged as being sulfurous. It had been a perfect ferment and aged for almost a year, so I believe whatever the judges tasted was due to my additions at bottling.The same cider after 2 months in the keg scored 10 points higher. And in a keg the air space is purged with CO2 so the chances of oxidation are low.

I do use a full dose when racking for aging, and that's generally 4 - 10 months before bottling.

Optimum SO2 level is pH dependent and my ciders are always below 3.5. I've not measured a mead yet - have you?

 

[NeverDie]

Optimum SO2 level is pH dependent and my ciders are always below 3.5. I've not measured a mead yet - have you?

Not yet. I will be soon though: I just recently acquired SO2 Titrets for that purpose.

 

[NeverDie]

I dosed a mead to 150ppm free SO2, and, unfortunately, the SO2 can be tasted (not a good flavor, either). Therefore, whatever the taste threshhold is, it's something lower than 150ppm.

So, at present, the prognosis doesn't look good for the brute force method of SO2 dosing.

Reporting back: I blended part of the 150ppm SO2 mead with a young new mead that hadn't yet been treated with metabisulfite in a 1:2 ratio, yielding a theoretical 50ppm SO2 in the combined, blended mead. It worked: the bad SO2 taste went away. It seems there was no permanent damage from dosing the SO2 too high (150ppm) on the first mead. Also, by inference, apparently 50ppm SO2 is below the SO2 taste threshhold.

 

[RPh_Guy]

50ppm SO2 is below the SO2 taste threshhold.

At that particular pH.

 

[NeverDie]

Reporting back: I tried the titrets. It seems mainly good for getting a ballpark number, and it's hard to get a more accurate number without knowing what the ballpark number is first. Otherwise, it might take 100 steps of letting minuscule amounts of the sample into the titret, waiting for the color to suddenly change. Also, it's hard to regulate just how much sample gets sucked in per step. Maybe with practice I would get better at that....

Another limitation is that the results aren't good if there is tannin in the sample. Given how important adding tannin can be for mead, that's a serious limitation.

 

[Maylar]

Bummer. There's always gonna be tannin in what I make. I'm thinking of mixing a Campden tablet in a gallon of water just to see what the kit reads it as.

And did you buy the titret holder gizmo? Reviews for the kit say you really need it.

 

[NeverDie]

And did you buy the titret holder gizmo? Reviews for the kit say you really need it.

Yup. Because I have it, I haven't tried without it. However, I'm fairly sure it's just a matter of bending the tube a little bit, which you could do yourself, to let in more sample. That's all that the titrettor does.

The valve leaked on the very first titret that I tried. If it wasn't sucking in sample, it was sucking in air. Just unlucky I guess. The other two titrets I tried afterward didn't share that problem.

I measured one mead at 16ppm sulfite. Afterward I ran it through my ChemDex coffee filter to filter out particles in it, and then I immediately tested it again: 14ppm. I had expected a much bigger drop than that given all the oxygen exposure. Maybe it takes more time than that for the newly acquired oxygen to react with and diminish the sulfite?

 

[B.rad0034]

It seems like stabilizing may (?) also help with clarifying the must. I had a couple of test batches that I cold crashed, with little to no visible improvement--still very cloudy. But after adding the stabilizing agents and continuing the cold crash, a lot settled to the bottom and they cleared up quite a bit overnight.

Is it better to cold crash first, as I did, or is it better to add the stabilizing agents and then cold crash? Or, does it make no difference? My theory was that the cold crash would weaken anything alive in the must, and the stabilizing agents would then be more effective if applied after the cold crash had been going for, say, 24 hours or longer.

Off gassing vastly improves your product to be clearer, faster. Swirl your product at least a minute every day getting rid of excess o2 (which is yeasts waste). The bubbles cause unwanted particles to be put into suspension over and over, thus off gassing is huge on clarity!