Testing Red Wine for Sulfur Dioxide SO2 ppm

If your pH is below 3.5, then 15ppm free SO2 is at the lower limit of adequacy, IMHO, as an antioxidant. You'll need progressively more free SO2 as the pH gets higher. Please note that the Ripper method commonly used for titrets and kits is not the most accurate, so you may want to shoot for 25-30ppm free SO2 to play it safe.

Seems like a lot of work to have different levels of SO2 in the different bottles. You probably won't taste the SO2 until at least 50 ppm, so how about putting 50 ppm free SO2 in all bottles you plan to age over a year? Some people I know don't taste free SO2 until over 100 ppm.

Gene

Posted this before but it didn't come through, so again - there is no point really in measuring SO2 levels while the wine is still fermenting as this one is. as a rule of thumn, you can assume there is prety much no free SO2 left after the ferment, do the the 1st sulfite addition based on that and only then start measuring if you want to keep precise control on the SO2 levels.

As Gene said, Ripper is known to exaggerate the levels, especially for red wines - the typical value I've seen around is 15-20ppm over the real level. So you should take that into account.

This being a Wineexpert kit, I think their standard recommendation is to add 1/4 tsp sulfite if you're bulk aging the wine before bottling, otherwise just follow the kit instructions. That said, there is no issue in fine-tuning the sulfite additions during bottling as Alan's asking about and it's not that much work - I'd just make sure to mark the different batches clearly to know when to open the bottle! If doing it this way, I'd shoot for something like +10ppm for 2 years aging, +25ppm for 5 years.

Lastly, are you sure the wine will last and improve in the bottle for that long? If not then go easy on the sulfite - oversulfiting is one of the most common winemaking mistakes and pretty hard to rectify.

Pp

How would I make a liquid "stock" solution for sulfite addition? My kit has two small packets, one is potassium metabisulfite and one of potassium sorbate. I'm thinking the first ten bottles get the recommended dosage of sulfite from the manufacturer, the next ten get 50 per cent more, and the last ten get double or 100 per cent the recommended dosage. My question again is how much sulfite powder do I weigh into say a 150 ml of water? I'm thinking thirds work best. Also, I don't know if my test kit is what you call a "Ripper". My test kit has be draw out 10ml of wine in a syringe, dilute it with 50mls of water. Add 1/8 of a teaspoon of "powder A" (labeled Oxalic Acid), swish, and then "powder B" (Don't know?). And then I swish it around and start adding drops of "Solution Y" (Don't know?) two drops at a time until the colour turns. Each two drops represents two ppm. Then I do a second test, nearly the same as the first except I add 25 drops of "Solution X" (Don't know?) and then add "Solution Y" until it changes colour. Then I subtract the ppm of the second test from the first test to establish the wine's ppm. It's a kit made by Spagnol's Beer and Wine Making in New Westminster B.C. here in Canada. Sound familiar? Thx.

"pp" wrote in message news: snipped-for-privacy@j27g2000cwj.googlegroups.com...

It does sound familiar as I'm actually pretty close to you - Burnaby - and visit that store 3-4 times a year. I've seen this one but haven't used it so can't really say for sure. I wonder if it's a proprietary product because I haven't seen it anywhere else. They also carry Titrets and that's what most people usually use unless they go with a full blown lab equipment. These are glass ampules that contain a test solution and you keep drawing sample wine into them until the colour changes. The test is based on the Ripper method.

I haven't seen oxalic acid mentioned anywhere in SO2 tests so can't say how the Spagnol's tests works - maybe somebody else knows here? For the test precision, you could test 2-3 batches of different wines with both methods and see how much the results differ. Or just calibrate based on the smell, taste and development of the wine - but it can take a while to relate those impressions to the sulfite levels.

For the stock solution - what works well for me is the method from Iverson's book. 1/4 tsp of sulfite powder gives about 50ppm free sulfite for 5 gals of wine, i.e., 25 bottles. So if I'm doing small additions for bottling, I'd dissolve the 1/4 tsp in 25ml of water. Adding 1 ml of the solution into a bottle then boosts the sulfite by

50ppm, so if I want to raise it by say 10ppm, I'd add 0.2ml. A 1 ml pipette works great for measuring this, a 1 ml syringe would probably work just as well.

If you do the additions to the bulk wine, you can use the same approach, just calculate for the # of gallons you have. There is no reason to add too much water to the sulfite powder - I find 20-25ml per 1/4 tsp is a good compromise in getting a decent precision and not diluting the wine unnecessarily.

Pp