What's the difference between red and black licorice, besides color?

This article appeared on Boston.com on August 29, 2011 and was written by Northeastern University physicist John Swain. E-mail questions to drknowledge@globe.com or write to Dr. Knowledge, c/o The Boston Globe, PO Box 55819, Boston, MA 02205-5819.

Real licorice, which is in black licorice candy, is made from the roots of the licorice plant, which can also be spelled liquorice.

Red licorice isn’t really licorice at all, except in name. It’s just a red candy, which can be made with many different flavorings, including strawberry, cherry, raspberry, and cinnamon.

Despite similarities in taste, licorice is not related to anise or fennel.

American, Chinese, and European varieties of the licorice plant are all slightly different but have many similarities.

Each variety is a legume. Each produces a compound in its roots called anethole, which gives black licorice its distinctive flavor. Each also produces a compound called glycyrrhizin, a substance that is 30 to 50 times sweeter than sugar.

Glycyrrhizin can have negative physiological effects, including raising blood pressure and causing water retention, so it’s a good idea to exercise some care in eating licorice, especially people with heart problems, who might want to consider having a chat with a doctor if they eat a lot of it.

Licorice root, which can be chewed for its taste and sweetness, is an integral part of Chinese cuisine and traditional Chinese medicine.

If you are fond of licorice candies, you might want to be aware that the ingredients used to make them can vary. European candies, for example, often are flavored with aniseed oil and may contain very little substance from licorice plants.