Rule #1: If you CAN measure it, you probably SHOULD measure it. If you CAN take a note you probably SHOULD take a note. You’ve nothing to lose, lots to gain, and if you go back and review once in a while you’ll learn a thing or two along the way.
After (or perhaps along with) pH, in my opinion, the most important number you should know about your wine is its SO2 level. Proper SO2 levels protect wine from spoilage organisms and the effects of oxidation without imparting an unpleasant chemical odor or taste. The good news is it’s easy to monitor. The bad news is that the test is a little pricey — a 10-pack of Titrets is now pushing $15 at the Flying Barrel in Frederick MD. Buck-an-a-half a pop. And when you’ve got 6 or 8 different wines in various stages of production those tests can add up over time.
Still, too much or too little SO2 can really impact the quality of your final product so judicious use and management of sulfites is essential. As an added benefit, taking these measurements allows you to develop a feel for how the sulfite levels vary in your wines as you process them. As your intuition develops you’ll be able to get away with fewer tests.
My company closes for the week between Christmas and New Year’s. The perfect time to devote a day to moving wine. The red grapes have finally completed malolactic and will be coming off their gross lees. The whites are coming off their fine. The early summer fruits are getting bright and the late fruits are clearing nicely. I have data points for all of these wines but I’ve decided today will be a day of documentation. I’ll check key metrics on each — temperature, specific gravity, pH, acid and, of course, free SO2.
Like I said, the test is easy. The Titret contains a reagent in a vacuum. The “probe” is filled with an indicator solution that attaches to the Titret via a ball valve. Simply slide the probe onto the Titret to the marked position and snap the tip of the Titret. Submerge the probe into your wine sample and squeeze the ball valve ever so briefly. The vacuum will draw the indicator solution and some wine into the Titret where it will mix with the reagent. The indicator will cause the reagent to turn blue. Using the ball valve, continue taking little “sips” of your wine sample until the Titret loses its blue-ish tinge and you’re left with the original color of your wine. That’s the end point of your measurement. Now just stand the titret up and read the free SO2 directly off the scale. It’s that easy! (Note: For deeply colored wines — cabs, merlots, etc. — I like to draw a sample into a syringe to use for color comparison so that I don’t overshoot the endpoint as I conduct the measurement.)
***Special Note: It’s July 2007 now and I’ve only just found out that carbohydrates (sugars and tannins for example) can skew Titrette SO2 measurements to the high side. This renders any tests on sweet wines and red wines suspect and, for all practical purposes, irrelevant. The only thing worse than no measurement is a measurement that misleads. Some of my measurements below are clearly of no value. So noted… ***
And so here are my wine rainbows. Pretty, I’d say, but are they art?? Well, probably not. But I may make the image my Windows desktop — at least for a while… 🙂 Represented here you’ll find Cabernet, Merlot, Chardonnay, Seyval, Wineberry, Blueberry, Strawberry, Plum and Cherry — some in more than one style. The tests came in from about 16 ppm to 50 ppm. And remember, higher pH wines require higher levels of free suphur dioxide to protect them from spoilage and oxidation. Given healthy pH values, let’s say 3.2 to 3.6, I like to keep my free SO2 levels at 25 to 50 ppm.
Want to know more? There’s plenty more to know! Here’s an excellent two-page primer on SO2 from Accuvin. Also be sure to see my Recommended Links below for one or two excellent SO2 calculators that you can download or use on-line. Enjoy!