In home wine making there are as many opinions about the use of sulfites as there are carboys. Some winemakers love em', adding Campden Tablets at every racking to ensure a wine that will age for the next 150 years. Routinely bathing hydrometers, thermometers, carboys and anything else that touch their wine, with sulfites. Other winemakers hate em', taking a more holistic wine making approach and shunning anything foreign, anything man-made. Making wine with off flavors that add "complexity" and are at risk of spoilage if not consumed within just a few months. Between these two extremes lies the reality of sulfites, to make consistent quality wine with a clean balanced taste you NEED EM'. Yes, we need them but with a gentle and balanced hand. This is where science and art mix, where the "love em' " and the "hate em'" crowd can find common ground to both make quality wine. In this article I am going to discuss this common ground. The science in using sulfites is easily defined, but it is up to you, the winemaker, to define the art.

Sulfites are nothing new to mankind. Ancient Egyptians used sulfites for disinfecting wine vessels; monks used sulfite in wine making as a preservative. This strange substance has been responsible for perfect wines and wines that are nothing more than science experiments gone awry. But what exactly is a sulfite and what does it do? For wine making, sulfites are broken into two categories, bound and free. Free sulfites come in the form of sulfurous acid, H2 SO3, or "molecular sulfite." It is this sulfite that has the ability to cross cell walls and destroy unwanted bacteria or bind with oxygen to prevent oxidation of the wine. If your grapes are infected with Botrytis, free sulfite can bind with gluconic acid to minimize its effects. The amount of free sulfites is also completely dependant upon the wine's pH. The higher the wine's pH the lower amount of free sulfite available to protect it. Federal regulations permit a maximum of 350 ppm of total sulfite in wine, but prudent winemakers will add the minimum necessary to achieve its antioxidant and anti microbial effects. What is that level and how do you get there?

Sulfites are commonly added two ways. The first is crushing Campden Tablets; the second is adding a measured amount of Potassium metabisulfite, known as K-meta. For this discussion we will examine the uses of K-meta in home wine making Winemakers who routinely measure their free sulfite levels will say that 40-ppm will protect their wine in the bottle from micro-organisms that can cause off odors and flavors. In the case of primary fermentation, if moldy or damaged fruit is used, this 40-ppm may not get the job done. On the front of LD Carlson's 2 oz. jar of K-meta they recommend .67 grams of k-meta per gallon of must to kill wild yeast. This works out to a sulfite concentration of 100 ppm. During primary fermentation, if making a kit wine, just follow the directions. If making a wine from fruit or juice, then things can be a bit tricky. Still the 40-ppm in the bottle is a great benchmark, but how do we get there?

To accurately determine the sulfite in your wine you will need a few tools. These tools can be found in George's on-line catalog. The first is Titrets from Chemetrics. You get ten tests to determine the ppm between 10 and 100. This kit is more accurate with white wines then red so your reds will have to be diluted to determine the sulfite level. For reds use a 50% dilution and watch for color change from blue to red, note this point and multiply the results by 2 to get the free sulfite level. To make this test more accurate you will also need the Titrettor accessory pack. This is a holder for the Titrets and allows better control while testing. The second tool is "Precision" pH control paper. This is paper that when dipped in a solution will give its approximate pH. PH levels depend on the style of wine. As a general rule of thumb use 3.2 for sweet, 3.4 for white and 3.6 for reds as a baseline in determining how much K-meta to add. You should target a free sulfite concentration 25% higher for each 0.1 pH increase above this baseline. Also pick up a small scale or medical grade teaspoon measurer for measuring out precise amounts of K-meta. The small scale works best but we are going to use the teaspoon measurer for this exercise. Now that we have all our components ready to go, what do we do with them? Take a moment to get comfortable, maybe pour another glass of your favorite homemade wine because here comes the MATH.

Lets make a couple of assumptions. The first is that you added some K-meta to the must 24 hours before pitching the yeast, lets say 1/4 teaspoon of K-meta for a 5-gallon batch. You've done your first racking from the primary to the carboy; your wine is clearing nicely and its time for another racking. Your first step should be to draw a sample and test with a pH strip. Then test with the Titrets kit. Lets say it's a white wine with a pH of 3.8 and sulfite at 20 ppm. If we are shooting for the 40-ppm sulfite benchmark then we will need to add enough K-meta to bring the sulfite up to 80 ppm. Remember the effect that pH has on sulfite: (3.8pH - 3.4 pH) = .4 pH difference...(.4 x 10) = 4...(4 x 25%) = 100%. So to get the effect of 40 ppm of sulfite in a wine we will need to achieve 100% more then 40 ppm, which is 80 ppm. If the wine had a 3.6 pH then it would look like this (3.6 - 3.4) = .2 pH...(.2 x 10) = 2...(2 x 25%) = 50%. So to get the effect of 40 ppm we would have to achieve 50% more or 60 ppm. Now lets compensate for the 20-ppm of sulfite already contained in the wine.

This is a pretty simple formula if you understand what the values mean. The basic formula is (ppm needed x liters of wine) divided by 0.57, if using K-meta. PPM in the equation is in decimal form, 60 ppm would be .060. To find out how many liters you have take the number of gallons times 3.785 liters per gallon. Five gallons of wine equals 19 liters. K-meta contains approximately 57% sulfite; this is where the 0.57 comes from. So using the first example above we start with 20 ppm. We need to add 60 ppm to get to the recommended 80 ppm based on the pH. Our equation now looks like this (.060 x 19) divided by .57 = 2 grams of K-meta. So if you had a scale you would measure out 2 grams of K-meta, dissolve it in water, add it to your wine then rack. If you are like me and do not have a scale its time to take out the trusty measuring spoon and do some more math.

K-meta averages 5.5 grams to 6.3 grams per teaspoon. I am going to use the lower end of 5.5 grams to do this math. All you do is take the amount of grams needed, in this case 2 grams of K-meta, and divide it by 5.5 grams per teaspoon. You come up with .3636 teaspoon or approximately 1/3 of a teaspoon. The 40-ppm is a general rule of thumb.

After examining our sulfite levels we are ready to put our math to a test. Last month we examined how to get various sulfite levels in our wine. Yes, this is great if we have all the testing materials, but what does this mean if we are just following directions in a wine kit, or are making our first homemade batch? I purchased a Titrets set from George and conducted a few experiments on my wine.

I tested a number of kits, store bought, and homemade wines. The results are certainly interesting and informative. I tested two kit wines, two store bought wines and two homemade wines.

Kit Wines: Both are Vintners Reserve Beaujolais’ kits. I picked these kits because they are very popular due to their early drinking. The first one I ruined because of cleanliness issues. The second one turned out great and I am enjoying a glass right now. Here are the results.

#1 – I added an extra 1/4 tsp. of K-meta to try and salvage the first wine, but I just sprinkled it on top and did not dilute it first. Using the Titrets from George I measured 40 ppm after approx. 5 months in the bottle.

#2 – For the 2nd VR Beaujolais kit I did not add any extra K-Meta. I followed the directions and did not add any extra K-Meta for aging. Using the Titrets kit I ended up with 36 ppm after approx. 2 months in the bottle.

Store bought wines: Both are whites from 2004. The first is Robert Mondavi’s reserve Riesling, the second is Covey Run’s 2004 Riesling. Mondavi’s is from California and Covey Run’s is from Washington.

#1 – Mondavi’s 2004 Riesling tested at 12 ppm using the Titrets set.

#2 – Covey Run’s 2004 Riesling tested at 12 ppm.

Homemade wines: I have made an apple/raspberry wine and an apple cider from juice.

#1 – The apple/raspberry was made from Wal-Mart apple juice and some frozen apple/raspberry concentrate. They both stated no preservative. After about 2 months of bulk aging the wine tested at 70 ppm. WOW!! No preservative? That’s what it said on the bottles of juice I used; don’t know if I believe it.

#2 – I made some apple cider and here are the results. Using Kroger apple juice I tested it twice at 100 ppm. The interesting thing about the cider is that I never added any K-Meta to the must. The only K-meta I used was to clean the primary and the carboy for secondary fermentation. I always rinse any residual K-meta from the surface using boiling water to ensure I get it rinsed clean. I used Champagne yeast to ferment the cider and can’t believe it would give off that much SO2.

I have come to a couple of conclusions concerning K-meta use in you wine.