So2

[Gardenfish]

This is in the newbee guide---

For wine: 1/8 teaspoon (1 gram) of powder per gallon of wine provides 150 ppm free SO2. A little bit goes a long way, so be careful! Generally speaking, the target free SO2 for red wines is 20-30 ppm and 25-40 ppm for white wines.
(Text from http://www.grapestompers.com/description_chem.htm).

So would one use 1 gram or per gallon(150ppm) or .2 grams per gallon(30 ppm) for red wine? Is this the same for honey?

Gardenfish

 

[Medsen Fey]

Hello Gardenfish,

It might be helpful if you post up your recipe/process details so we can see what you are working with. Also, it is key to know the pH.

Do you have the testing supplies to measure the free SO2?

Medsen

 

[Gardenfish]

I was reading this as a general statement. I am assuming it shows the ppm for a gram as a reference point and that the ppm's given for reds and whites are a general guidline for each variety. I have not sulfited any of my batches so far and do not know that I will. I am thinking of adding some strawberry juice to the secondary of my Gardenfishes Yo's strawberry batch and since the alc is already 17.2% I may want to sulphite to keep it from going further and helping with oxidization. I will study the pro's and con's further and listen to any and all advise before I decide. I do not have anything to measure so2. What kind of kit would I need?

Thanks,Gardenfish

 

[Medsen Fey]

I am assuming it shows the ppm for a gram as a reference point and that the ppm's given for reds and whites are a general guidline for each variety.

I am thinking of adding some strawberry juice to the secondary of my Gardenfishes Yo's strawberry batch and since the alc is already 17.2% I may want to sulphite to keep it from going further and helping with oxidization.

I do not have anything to measure so2. What kind of kit would I need?

For some in depth reading on sulfites, check the link in This Thread. In part 17, they talk about recommended amounts.

The PPM concentrations of free SO2 you have listed are very general and apply for dry wines. If there is residual sugar the required level will run higher. As I mentioned, the pH is a major factor as the lower the pH, the more of the SO2 is in the molecular (active) form. This calculator can help you derive the amounts need for your goal, and there is table (if you scroll down) that shows the effect of pH. To maintain a molecular SO2 of 0.8 PPM (a typical goal for microbial stability) at a pH of 3.2 you need 21 PPM of free SO2, whereas at a pH of 4.0, you need 128 PPM of free SO2 (a 6-fold difference).

High pH wines are hard to keep stable, and I expect that meads are similar especially with fruit and/or residual sugar. Sulfite alone may not be enough to keep a mead with residual sugar from refermenting if you don't use sorbate as well, but that depends on many factors.

To measure the free SO2 the most common way is the Ripper method. There are titrets you can use. I happen to use the Vinoferm test kit for both TA and Free SO2 (you have to buy the iodic solution for SO2) as I find it very easy to use. Accuvin test kits are also simple. All of these kits use the same method, which may have accuracy of +/- 10 PPM easily, so we are not necessarily as able to be as sure of our targets as you might like. This is especially true when you consider that your pH meter may have accuracy of +/- 0.1 or more (a good argument for buying a pH meter with an accuracy of 0.01 which cost a little more).

More accurate results can be obtained using the aeration oxidation method, but you can read up on that. Easier (but costly) is to send a sample to a lab where you can get accurate testing.

If this didn't make it complicated enough, using it with sweetened meads you'll find the sugars and gluconolactone will bind a considerable amount of SO2 (which won't be measures as "free" with the test kits). These bound forms may still prevent bacterial infection, however they won't be effective at preventing yeast activity. That may be okay and having a lower free SO2, you can still have enough to have some antioxidant activity.

The use of SO2 in mead making is a topic that is wide open for experiments and testing. I suspect we will find that the behavior differs somewhat from wine due to the honey components such as gluconolactone. If I've made it sound more complicated than it has to be, well... that's just me. Some folks take a simple approach - 1 Campden tablet per gallon (440 mg of potassium metabisulfite) at the time of racking, and perhaps re-additions after every other racking. This may work, but you may grossly under or over shoot the mark. I think it is worth taking the time to measure and get the level where you want it.

I hope that helps.

Medsen (not a bigwheel, but definitely going in circles) :laughing6:

 

[afdoty]

and there is table (if you scroll down) that shows the effect of pH. To maintain a molecular SO2 of 0.8 PPM (a typical goal for microbial stability) at a pH of 3.2 you need 21 PPM of free SO2, whereas at a pH of 4.0, you need 128 PPM of free SO2 (a 6-fold difference)
:

Since the topic came up, I’ll ask a question. Lets say you stabilized at PH 3.2 and then, later, raised the PH 4.0. Besides tasting like Potassium Bicarbonate, would it be any more/less stabile compared to mead stabilized at an original PH of 4.0?

 

[wayneb]

I'll jump in here by saying that your stability will vary with time, as the free SO2 contributed by any sulfite addition will attenuate over time, since the sulfur dioxide comes out of solution and dissipates in the air. The antimicrobial activity of any mead with sulfites added will thus diminish over time, and that makes the comparison you're asking about a very difficult one to quantify.

That said, higher pH is problematic for several reasons. Not only does it require substantially higher doses of metabisulfite to get a sulfite level capable of exhibiting antimicrobial activity than when the pH is lower, but starting at a pH of about 4.0 and higher another whole class of different microbes can begin to infect your must. Lower pH meads are inherently more stable, all other things being equal.

 

[afdoty]

I'll jump in here by saying that your stability will vary with time, as the free SO2 contributed by any sulfite addition will attenuate over time, since the sulfur dioxide comes out of solution and dissipates in the air.

Got it! Thank you.