All citrus fruits contain ascorbic acid, also called vitamin C, and are considered acidic fruit. The higher the ascorbic acid content, the better the taste and quality of the fruit. Oranges, lemons, limes, grapefruit and other citrus fruits are among the most detoxifying foods and also contain other important nutrients such as vitamin A. Citrus fruits also contain citric acid and pantothenic acid, which is a B vitamin that helps to oxidize fats, carbohydrates and some amino acids.
Ascorbic acid, or vitamin C, has a chemical makeup of C6H8O6. The amount of ascorbic acid in citrus fruit depends on several factors. When fruit such as oranges are picked late in their season, the concentration of ascorbic acid is lower than in fruit picked earlier. Cultural practices, such as how much water and fertilizer the tree received during its growing season, also affect ascorbic acid content. For example, when trees are given fertilizers that are high in nitrogen, the fruit will have a lower acid content. Temperature also affects ascorbic acid content. When citrus fruit is grown in places that have cooler nights, vitamin C content is higher than in fruits grown in tropical locations. The fruit is not the only place where ascorbic acid is found in citrus fruits--up to 75 percent is located in the peel.
Citric acid has a chemical makeup of C6H8O7, one more oxygen atom than ascorbic acid. It is found in all citrus fruits and some other foods. Lemons and limes have the highest citric acid content of the citrus fruits. Citric acid is a white powder at room temperature and then it crystallizes when added to hot water. It is added to processed food products such as fruit- flavored candies, soft drinks and sourdough breads because it helps to enhance their tart flavors.
Lemons and Limes
Lemons and limes are the winners in the citrus acidity count. Vitamin C (ascorbic acid) can comprise up to 32 percent of the fruits’ weight. Lemon juice contains 187 percent vitamin C. Citric acid makes up 5 percent to 6 percent of the fruits’ content. Lemons contain approximately 3 percent pantothenic acid. Fresh lime juice contains 121 percent vitamin C and 1 percent pantothenic acid.
Oranges have the smallest concentration of vitamin C of all the citrus fruits. One medium orange typically contains between 50 and 70 mg of vitamin C. Oranges also have .08 to 1 percent citric acid. Different varieties of oranges have differing amounts of vitamin C. The cultivar “Pineapple” has the most, followed by the Hamlin variety. Valencia oranges, the most common oranges grown for their juice, have the lowest amount of vitamin C. Orange peel has 53 percent of the fruit’s vitamin C, while the juice contains 26 percent ascorbic acid. The pulp and “rag” have 21 percent.
Grapefruit, Tangerines and Other Citrus
Grapefruit is higher in vitamin C than oranges, second only to its citrus relatives lemons and limes. One cup of measured segments contains 120 percent vitamin C, 1.5 percent to 2.5 percent citric acid and 7 percent pantothenic acid. Mandarin oranges, tangelos and most other types of tangerine-type fruit must have 8 percent acidity in order to be considered for the commercial market. Their vitamin C content is 87 percent, which is typically lower than oranges because tangerines have lower acid levels overall.