Citric acid and its salts are found naturally in citrus fruits, tomatoes, coffee, apricots, peaches, pineapples, and some berries.  In food processing, citric acid or sometimes, its salts are used as a flavoring agent or enhancer to impart a tangy, tart, or sour taste to foods, including beverages, candy, ice cream, baked goods, and chewing gum.  

Citric acid is also used as a buffer to maintain acidity in foods such as fruit juices, carbonated beverages, wines, jellies, and sherbet. 

As a sequestrant, it removes metal contaminants from food and allows preservatives to work better, maintaining food flavor.  Calcium citrate is used as a firming agent in canned tomatoes, and the citric salts, such as calcium, are a vehicle for adding various mineral nutrients.

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