Lemon juice has been valued for culinary, cosmetic and medicinal uses for thousands of years. Added to food, this citrus juice imparts a sharp, sour taste, while helping preserve the ingredients by preventing the process of oxidation that causes food to spoil. Lemon juice owes many of its characteristics to the acids it contains.
Lemon juice is a tangy, acidic liquid extracted from the fruit of the lemon tree, Citrus limon. The lemon is a small, light-yellow fruit with a pungent rind (peel) that contains pale yellow segmented pulp that holds the fruit’s juice. A medium lemon yields between 2 and 3 tbsp. of lemon juice, according to Food.com.
The lemon is native to the southern regions of Asia, from where it spread to the Mediterranean region, the Middle East and Northern Africa, according to the George Mateljan Foundation. It was first cultivated in America when Columbus arrived in the New World with lemon seeds in 1493 and planted them in Haiti. Today, it is widely distributed in numerous warm, sub-tropical regions of the world.
An acid is a compound with a sour taste that turns blue litmus paper red, writes the Physical and Theoretical Chemistry Laboratory at Oxford University, England. Depending on the temperature, acid can be in liquid, solid or gaseous form. An acid’s strength is measured in terms of its pH, or power of hydrogen, which is a numerical value denoting its hydrogen ion concentration. The more acidic a compound is, the lower its pH.
Lemon juice is a very acidic fruit juice with an average pH of 2.3, writes Robert Clemens in his book “Organic Acids in Citrus Fruits.” He notes that citric acid is the predominant organic acid in it, with smaller but significant amounts of ascorbic acid (vitamin C). The juice also contains malic acid. According to a study by the National Institutes of Health, lemon is a rich source of citric acid, containing 1.44 g per ounce. The USDA National Nutrient Database reports that each cup of lemon juice contains 112.2 mg of ascorbic acid and 0.251 mg of pantothenic acid.
Drugs.com cautions that citrus juice is often associated with aggravating the symptoms of GERD, or gastroesophageal reflux disease, a chronic digestive disorder that results when stomach acid flows backward (refluxes) into the food pipe. It also might erode or discolor tooth enamel.