It’s fairly common for beginner home winemakers to hear intimidating, chemically-sounding terms like “postassium metabisulphite” and wonder if they are adding dangerous compounds to their wine. It’s natural to have concerns, but you might be surprised to learn that sulphites are also natural.
What Are Sulphites?
First of all, it’s interesting to note that sulphites are natural in that they occur in nature. In fact, sulphites occur in wine as a byproduct of fermentation, even if no additional sulphites are added. During fermentation, yeast metabolizes the sugars in grape juice, producing not only alcohol and carbon dioxide but also small amounts of sulphur dioxide (SO₂). This natural production of SO₂ serves as a microbial preservative and antioxidant, contributing to the wine's stability and longevity. Consequently, all wines, even those labeled as "sulphite-free," contain some level of naturally occurring sulphites due to the yeast’s metabolic activity.
Okay, so sulphites occur naturally, but what are they? Sulphites are compounds that contain sulphur dioxide (SO₂), which is widely used in winemaking as a natural preservative and sanitizer. Common forms include potassium metabisulfite and sodium metabisulfite. In home winemaking, they are generally used interchangeably.
Why Are Sulphites Used in Winemaking?
- Preservation:
- Prevent Oxidation: Okay, so whenever we use the term “preservative” things start to sound scary, and perhaps rightfully so, because the industrial food producers do in fact put some scary compounds in our food. But when you think of sulphites, think of antioxidants like ascorbic acid, also known as vitamin C. Sulphites are powerful antioxidants, and thus they protect wine from oxidation, which can spoil the wine’s flavor and aroma and lead to browning. Sulphites help maintain the wine's freshness and longevity.
- Inhibit Microbial Growth: Sulphites prevent the growth of unwanted bacteria and wild yeast, which reduces the risk of spoilage. With the bad guys out of the way, our yeast can ferment the wine correctly.
- Sanitization:
- Equipment Sanitizer: Winemakers often use sulphite solutions to sanitize winemaking equipment, which helps eliminate harmful microorganisms that could contaminate and produce off-flavors in our wine.
Are Sulphites Safe?
- Regulated Use:
- Safety Standards: This brings to mind thoughts like “everything in moderation”, or “too much of a good thing.” Vitamin A is necessary for survival, but too much can kill you. Arctic explorers learned this the hard way after eating the liver of polar bears. Sulphite levels in wine are regulated by food safety authorities worldwide, including the FDA in the United States and the European Food Safety Authority (EFSA). These regulations make sure safe amounts are used for consumption, and that’s a good thing.
- Typical Levels: Most wines contain sulphite levels well within safety limits. For example, commercial wines typically contain between 20-200 parts per million (ppm) of sulphites, with the upper limit for most wines being around 350 ppm, and most home winemakers use way less than that. One Campden tablet per gallon of wine produces a mere 30 ppm. To put this in perspective, dried apricots or sun-dried tomatoes can have suphite levels above 1000 ppm. Also, wine doesn’t require high levels, and at high levels, you would taste the sulfur, and wine makers do not want to taste sulfur. Thus, sulphite levels in wine are typically many times lower than what’s found in different types of food.
- Common Misconceptions:
- Allergies and Sensitivities: Some people have sulphite sensitivities or allergies, but these allergies are relatively rare. Compare this to lactose intolerance. Many estimates place worldwide lactose intolerance near 75%, yet milk doesn’t get a bag rap. For those with Sulphite sensitivities, symptoms may include headaches, hives, or asthma-like reactions. However, for most people, sulphites in wine pose no risk. Many people who drink wine and report headaches wrongfully attribute their headache to sulphites when in fact they are having a reaction to natural histamines found in wine, which is greater in red wines.
- Natural Occurrence: Sulphites occur naturally during the fermentation process, so even wines labeled as "sulphite-free" will contain trace amounts of naturally occurring sulphites.
- Moderation:
- Safe Consumption: We are repeating what we said before. Everything in moderation. When used correctly and in moderation, sulphites help produce high-quality, stable wine without posing a danger to the wine maker or drinker. If you used sulphite levels in your wine where you began to taste it, that level would still be an order of magnitude less than what you would find, for example, on dried apricots.
So What Have We Learned?
Yes, there are many scary things in the world, but sulphites are not one of them. Okay, I admit that sulphites have an image problem in that the name sounds too industrial. Maybe sulphites could benefit from some professional marking, and perhaps a stylist. Maybe if we changed the name from “sulphites” to “fuzzy bunny slippers”, then everyone would feel that “warm fuzzy” feeling using sulphites for the first time. So remember, sulphites are a natural and essential additive in both home and professional winemaking. Sulphites help protect the wine’s quality, prevent spoilage, and maintain its freshness for long-term aging. So I guess we can relax and tip a glass to that!