That tangy flavor found in some of the foods you eat may be due to citric acid, a naturally occurring acid found in many foods, most notably citrus fruits. Food manufacturers use citric acid both as a flavor enhancer and as a preservative in a variety of foods, including jams, jellies, and canned fruits and vegetables.
The United States Food and Drug Administration considers citric acid to be safe when used as a food additive. Typically, a person consumes about 500 mg citric acid per day, which is about the same as two ounces of orange juice. You also have citric acid in your body, as part of normal metabolism and in bone health.
Citric acid appears to be perfectly safe, but there are some anecdotal reports of people who are sensitive to foods that contain citric acid.
United States Food and Drug Administration. "Citric acid." Accessed August 21, 2009. http://www.accessdata.fda.gov/scripts/fcn/fcnDetailNavigation.cfm?rpt=scogsListing&id=82.