Citric Acid In Citrus Fruits

Citric acid gives fruit such as lemons, limes and grapefruit their sour tang. Until scientists discovered how to synthesize this acid, natural lemon juice was the only source of this useful flavoring agent. Today, citric acid gives soda its tang and helps create the bubbling reaction in effervescent antacids.

Identification

Citric acid occurs naturally, found in citrus fruits such as lemons, limes, grapefruits and oranges. According to Professor Oliver Seely, Jr. of California State University Dominguez Hills, all citrus fruits contain some degree of citric acid. Represented by the chemical formula C6H8O7, citric acid contains three carboxylic acid groups, each with a hydrogen atom that readily attaches to a hydroxide ion. To neutralize citric acid, scientists add a hydroxide solution to create a stable water molecule.

History

According to Michael Mattey and Bjørn Kristiansen in "Citric Acid Biotechnology," a Swedish scientist named Carl Scheele was the first to isolate citric acid from lemon juice in 1784. At that time---and until 1919---commercially harvested lemons were the only source of citric acid. In 1919, scientists discovered how to synthesize the acid in a laboratory using the "Aspergillus niger" fungus, ending the dependence on actual fruit for acid production.

Citric Acid in Food Production

The European Citric Acid Manufacturers' Association, ECAMA, notes that citric acid is most often used to flavor soft drinks, giving them a fresh, tangy taste. Most soft drinks include between 0.25 and 0.4 percent citric acid. Candy manufacturers also use citric acid as a flavor enhancer, especially for fruit or berry flavors. Citric acid functions as a preservative for canned fruits and veggies as well as a stabilizer for the emulsified fat in processed cheese.

Citric Acid in Effervescent Tablets

Citric acid is present in effervescent antacids and denture cleaners. According to Amerilab Technologies, citric acid is regularly used as the acid that, along with a base such as sodium bicarbonate, produces carbon dioxide when placed in water. The acid not only provides a citrus flavor that helps digestible medicines go down a little easier, but it also has a high water solubility, making it a better choice than tartaric acid or adipic acid.

Fruit Acid Levels

Not all fruits contain the same level of citric acid. According to a study published in the "Journal of Endourology" in 2008, lemon and lime juice contain the most citric acid whether the juice is freshly squeezed or from a concentrate. The study found little difference in the citric acid content between lemons and limes, lemons with 1.44 grams per ounce and limes with 1.38 grams per ounce.

Store-bought grapefruit juice, store-bought orange juice and fresh-squeezed orange juice all contained less citric acid than lemons or limes. Surprisingly, store-bought lemonade and powdered lemonade mixes contained, on average, six times less citric acid than fresh lemon juice.