Does it make a difference if I buy apricots preserved with sulfur dioxide versus those that aren't?
Most of the prepackaged, bright orange dried apricots for sale in mainstream supermarkets have been treated with a preservative called sulfur dioxide. All of the food scientists we consulted agreed that sulfur both preserves the natural orange color of the fruit and fights against the development of mold. It does so by drastically slowing the activity of an enzyme in the apricots called polyphenoloxidase, which oxidizes other compounds in the plant tissue and creates brown and gray pigments. (Incidentally, the same browning compounds are also present in apples, pears, bananas, avocados, and potatoes, among other foods.) The use of sulfites is regulated by the Food and Drug Administration and is generally considered safe, though sulfites have been known to produce allergic reactions in some people, especially those who suffer from asthma.
We taste-tested prepackaged dried apricots preserved with sulfur dioxide side by side with some organic, unsulfured dried apricots we bought at a natural food store. Honestly, the unsulfured apricots were thoroughly unappealing—dry, shriveled, brown, and sour tasting. At a quick glance, one test cook mistook them for dried mushrooms. By comparison, the apricots treated with the preservative were bright orange, plump, moist, and sweet, by far the better choice for eating out of hand. Dr. Barry Swanson, professor of food science and human nutrition at Washington State University in Pullman, explained that the sulfur dioxide also limits the reaction of amino acids with glucose and other sugars in the fruit. This leaves a larger portion of the natural sugars in the fruit intact. So, in fact, apricots with sulfur dioxide may taste sweeter than their unsulfured counterparts.
Dr. Swanson did warn, however, that the two types of apricot may well have been different varieties, harvested at different stages of maturity, and dried for different lengths of time at different temperatures. In short, to make a definitive assessment, we would have to begin with the same product, and there is no guarantee that we did. We simply used what was available at stores in our neighborhood. Steve Kollars, director of product development for Sunsweet Growers in Yuba City, California, confirmed Dr. Swanson's hunch, saying that our samples were indeed different varieties.
The sulfured apricots were grown in Turkey, and Mr. Kollars characterized them as more sweet and bland than the varieties grown in California, our unsulfured specimens, which he described as more acidic. With regard to texture, Mr. Kollars explained that that the use of preservatives allows the fruit to be processed with more moisture, making for a plumper end product.
All of the above information notwithstanding, we went ahead and made coffee cake fillings out of both types of apricot, and we were truly shocked by the results. The mixture made from the Californian unsulfured apricots was indeed brown—it looked more like prune filling than apricot—but the flavor was fantastic. It tasted bright and truly of apricot, with a great balance of tart and sweet. The mixture from the preserved Turkish apricots was an attractive orange, but its flavor was dull and overly sweet by comparison. If you can overlook the ugly brown color of the former and don't wish to snack on the apricots as you cook, we recommend Californian unsulfured fruit for this recipe. Look at the label on the bulk bin in the store where you make your purchase; the apricots' point of origin is usually listed.