Chances are you’ll see sodium acid pyrophosphate or sodium bisulfite listed on the label of a package of frozen French fries. They’re added to deal with that bane of potato lovers, the dark, gray tuber. This discoloration is due to a chemical reaction between iron and chlorogenic acid, natural components of a potato. In a freshly cooked potato these form a colorless complex which then turns gray on exposure to oxygen in the air. The color is unappetizing but has no detrimental effect on health or nutritional value. Sodium acid pyrophosphate and sodium bisulfite both bind iron and prevent it from reacting with chlorogenic acid. Some people are allergic to sulfites and have to be aware of their possible presence in French fries. Interestingly, chlorogenic acid is also found in green coffee beans and has been claimed to be the reason that green coffee beans are of help in weight loss. There is insufficient evidence to make this claim but that hasn't stopped marketers from jumping onto the driver's seat of the green coffee bean bandwagon. The passengers who climb on will be falling off.