In the 18th century, sailors discovered that citrus fruits could eliminate scurvy. The word "ascorbic," as in ascorbic acid from vitamin C, means "no scurvy." British sailors were called limeys for carrying large stores of limes aboard ships as a source of vitamin C. One orange can supply 116 percent of the daily value for vitamin C. However, vitamin C is very sensitive to heat, light and oxygen, which can deplete nutritional content.
Identification
Vitamin C is critical to life, and many mammals--with the exception of man, other primates and guinea pigs--can synthesize it from glucose. Humans need to rely on external sources for vitamin C's antioxidant benefits, which help provide some protection from cancer, cataracts and cardiovascular and joint diseases. Citrus fruits such as limes, lemons, oranges, grapefruits, tangerines and the juices made from these fruits are excellent sources of vitamin C.
Growing Factors
The use of fertilizers, especially nitrogen, can lower the content of vitamin C in citrus fruits. Potassium in soil also influences vitamin C levels. Climate is a factor; areas with cool nights produce citrus fruits with the highest vitamin C.
Harvesting
Vitamin C content changes throughout the harvest season of citrus fruits. As fruit ripens, it loses vitamin C. Immature fruit has the highest level. Fruit positioned on the sunny side of trees has more vitamin C.
Varieties
Each variety of oranges has different vitamin C content. Early-maturing varieties have the highest levels. For example, navel oranges have more vitamin C than late-maturing Valencias. Additionally, the longer the Valencia orange stays on the tree, the lower the vitamin C content.
Processing
About 25 percent of vitamin C can be lost by boiling or steaming food. Longer cooking times can result in a loss of more than half of vitamin C, according to the website whfoods. Because vitamin C levels degrade faster in fresh juice, orange juice from frozen concentrate contains more vitamin C, usually providing at least 100 percent of the recommended daily amount. Some vitamin C is lost in canned orange juice due to heating during the canning process.
Containers
There is a higher loss of vitamin C with enamel-lined cans than with plain tin cans because of vitamin C reaction with tin. Orange juice in glass containers loses 10 percent of vitamin C after four months of storage. Cardboard cartons lose up to 20 percent. Cartons that have specially designed oxygen and light barriers protect against rvitamin C loss and extend shelf life. Frozen orange juice in foil-lined cardboard cans loses less than 10 percent of its vitamin C after 12 months at -4 degrees F.
Storage
Oxygen destroys vitamin C. According to an article in the Journal of Agriculture Food Chemistry, cardboard orange juice containers lost vitamin C due to oxidation by residual air trapped in the container during processing. The loss was faster in the first two weeks and accelerated with higher storage temperatures. According to Ultimate Citrus Page, "When fresh citrus is stored at 38 degrees F for 12 weeks, there was no loss of vitamin C, but when stored at high temperatures, the loss was great." For optimum vitamin C intake, eat raw fruits as soon as possible after purchase. Cut fruit just before eating. Store fruit in the refrigerator.
Member Comments