Author explains sulfite uses

Some dried fruits are treated with sulfites to retain the vibrant natural color of the fruit, which would otherwise be lost during the drying process.

Sulfites are antioxidants that retard the oxidation of fruit which results in its characteristic browning of fruit when exposed to the air, according to Robert Wolke, author of “What Einstein Told His Cook: Kitchen Science Explained” and a columnist for the Food section. Sulfites are also antibacterial and, consequently, help to prevent spoilage.