Also known as glucitol
Sorbitol is a polyol (sugar alcohol) that is found naturally in a number of fruits, including apples, pears, and plums.
Sorbitol has a clean, sweet taste. It is about 60% as sweet as sucrose on a weight basis.
Sorbitol is only partly absorbed by the body, and its absorption is fairly slow. Absorbed sorbitol can be converted to glucose. Its caloric value depends on several factors, including how much is consumed, and individual variation in absorption rate. In the United States, sorbitol provides 2.6 calories per gram for labeling purposes. In the European Union, it is listed at 2.4 calories per gram.
Sorbitol behaves much like sucrose in food systems, with respect to providing bulk and interacting with other components to produce suitable texture. It is particularly good at binding moisture (humectant activity).
Sorbitol and the other polyols generally do not participate in browning reactions that provide characteristic color to baked goods.
The human body can absorb sorbitol and convert it to glucose, but it does not do so efficiently. Unabsorbed sorbitol can cause some digestive system unhappiness, including gas, rumbling sounds (borborygmus), and diarrhea. You can read about this in my recent essay, "Polyols--Digestive Issues".
Sorbitol is a common ingredient in sugar-free chewing gum.
The laxative effect of prunes is due to a combination of the fiber content and the sorbitol present in the fruit. Plums will have the same effect, but it's easier to eat 5 or 6 prunes than to eat 5 or 6 plums.