Do all wines have Sulfites?
Yes - Sulfites are a natural byproduct of the fermentation process. According to Professor Roger Boulton, Ph.D., University of California at Davis, even if no sulfur dioxide (SO2) is added to wine, fermenting yeasts will produce SO2 from the naturally occurring inorganic sulfates in all grape juices. Fermenting yeasts present on all grape skins generate naturally occurring sulfites in amounts ranging from 6 to 40 parts per million (ppm.) Thus, says Boulton, it is impossible for any wine to be completely free of sulfur dioxide.