Sulfite-free wines can be very interesting. I have been making them in California for 13 vintages, and have been able to achieve a degree of aromatic flavor interest and cellar longevity considerably beyond their sulfited counterparts. According to the elaborate research by William Younger in Gods, Men and Wine, the Romans had sulfites but chose not to use them on wine. From my own wines, I can see why. In my own wines, I choose to achieve a balanced microbial equilibrium rather than to sterilize the wine, but I can understand why other winemakers would want to use PCT technology, which has proven itself in fruit juices for twenty years.
There is no such thing as a sulfite allergy. SO2 is too small a molecule to be recognized by a T-cell, and the human body produces a gram per day of sulfites. There are other sorts of possible sensitivities such as a deficiency of sulfite oxidase enzyme in the liver, but these are exceedingly rare and to my knowledge have only been demonstrated in five U.S. citizens. For these people, the tiny amount of sulfites in a wine is the least of their worries.
Two articles I wrote about sulfur dioxide in 1982 for UC Davis Enology Briefs became very popular, but they contained a number of false or misleading statements which I corrected in "Sulfur Dioxide Revisited" in Wines and Vines magazine. In 1999, Dr. Lonvaud-Funel at the University of Bordeaux demonstrated that in red wines, SO2, which is entirely bound to pigments, was ineffective against Acetobacter. These organisms are suppressed instead by red wine’s oxygen-scavenging ability via phenolic oxidative polymerization, which is amazingly strong in well made wines. Dr. Vern Singleton at UC Davis demonstrated in 1987 that far from acting as an anti-oxidant, SO2 lowers the effectiveness of this reaction ten-fold or more by short-circuiting the wine’s oxygen uptake mechanism, an effect further researched by Dr. Andrew Waterhouse at UCD.
Supporting documentation can be downloaded from my Dropbox .
It is important for winemakers to understand that sulfite-free red wines, rather than being prone to oxidation, will be inclined towards serious reduction problems that may take many years in the bottle to overcome.