Citric Acid in Fruits

It's used as a cleaning agent, food preservative and gives your fruits their tart taste. Citric acid is a component of many fruits and vegetables in varying amounts to provide a flavor profile that can make your mouth pucker. Knowing how much citric acid is in different foods can help you understand why they taste the way they do.

Significance

Swedish chemist Carl Wilhem Scheele first isolated citric acid in 1784 from lemon juice, which has one of the highest percentages of citric acid. The acid is an organic compound, which means it contains carbon and occurs in nature. While you can find citric acid in fruits and vegetables, animal tissues also carry the acid. Today, citric acid can be created by combining cane sugar or molasses with the fungus Aspergillus niger. This chemical reaction produces a colorless, crystal-like compound that can be added to beverages, candies and other foods to give them a tart and/or sour taste.

Lemons and Limes

Fruits highest in citric acid tend to be citrus fruits, which are colorful fruits traditionally grown in warm climates. Citric acid can make up as much as 8 percent of the dry weight of lemons and limes. Lemon juice contains about 1.44 grams per ounce of citric acid, while lime juice has about 1.38 g/oz. This explains why lemons and limes tend to have a tart and/or sour flavor. The high concentration of citric acid means lemons and limes are rarely eaten whole, but instead diluted when squeezed into beverages or other food recipes.

Grapefruits and Oranges

The next-highest citric acid-containing foods tend to be grapefruits and oranges. Grapefruit juice contains about 0.75 g/oz. of citric acid -- almost half that of lemon juice. Orange juice has about 0.50 g/oz. of citric acid. The lower citric acid content is why both oranges and grapefruits are more suitable for being eaten as a whole fruit than lemons or limes.

Other Fruits

While most fruits contain some level of citric acid, other fruits, such as apples, cranberries, peaches, pears, raspberries and strawberries, are considered to be more acidic than low-acid fruits such as melons, bananas, figs and Asian pears.

Considerations

One of the reasons it is important to be aware of citric acid is that increased intake of citric acid is associated with a reduction of kidney stones. Citric acid is converted into citrate -- a mineral -- in the body and can bind with other minerals such as calcium and oxalate, which can cause kidney stones. The citrate encourages the minerals to be released from the body instead of building up and leading to kidney stones. Lemon juice has the most beneficial effects because it has the most citric acid -- try adding 4 oz. of lemon juice to about a half gallon of water and drink each day to reduce kidney stones, recommends Dr. Roger Sur, a researcher at the University of California-San Diego.