Sulfur dioxide is used as a preservative in dried fruit to prevent it from spoiling, and also to preserve the fruit's gorgeous and appetizingly bright color. That's why unsulfured fruits tend to look brownish or black. It sounds gross, but sulfur dioxide is a gas that's created by burning coal or oil, which both contain sulfur. UnSulfured dried fruit is dried in natural sunlight to remove excess water content and to prevent it from spoiling. which is healthier compared to Sulfured dried fruit.