Citric acid is a natural preservative, flavoring, and antioxidant. It exists naturally in citrus fruits, pineapple, berries and cherries, tomatoes, and cheese. Lemons and limes contain particularly high concentrations.
In the food industry, citric acid adds a sour taste to sodas, canned tomatoes and tomato sauces, canned fruit, jams, and some fruit-bottomed yogurts. It is denoted by E330 on labels.
Highly biodegradable citric acid also serves as an environmentally-friendly cleaning agent, acting as a scale-dissolver and buffer.
Overall, citric acid is a safe and natural additive. While allergies are rare, symptoms may include sore throats and mouth ulcers. Those experiencing allergies to citric acid in food products will notice similar symptoms from eating citrus fruit.