What Makes Fruits Lose Vitamin C?

Since before Hippocrates first described the condition, scurvy-afflicted sailors and other people who went months without vitamin C experienced loose teeth, bleeding gums and painful skin rashes from a disease known to the Romans as scorbutum. Researchers didn't understand the cause of the disease until the early 20th century when vitamin C was first discovered. Vitamin C's scientific name, ascorbic acid, literally means "without scurvy." While full-blown cases of scurvy are rare today, how you store and cook your food can maximize the vitamin C it retains and ensure that your food gives you sufficient ascorbic acid.

Water

Water-soluble vitamin C readily leaches out of fruits and vegetables when they soak in water. That includes water used for cooking and rinsing, so limit the amount of time your fruit spends in water if you want to maximize the vitamin C it retains. Boiling and stewing also reduces the ascorbic acid in food, so if you're going to cook your fruit, choose dry cooking techniques such as roasting, baking, grilling or sauteing to keep the food's vitamin C content intact.

Heat

The act of cooking foods also reduces their vitamin C content. For fruit, this may not be much of an issue. Most of the fruits that are richest in vitamin C -- citrus fruits, kiwi, guava and strawberries -- typically reach the plate raw. However, turning these fruits into sauces or preserves lowers their available ascorbic acid. Fruits that you use as vegetables such as peppers and tomatoes can suffer major vitamin C loss through cooking. Whenever possible, enjoy fruits rich in vitamin C in their raw state.

Light

Storing fruits rich in vitamin C in strong light also reduces their nutrient content. Light oxidizes the fragile vitamin, slowly depleting the fruit's natural reserves of ascorbic acid. Fruits with a thick inedible rind suffer less vitamin C loss than thin-skinned fruits that you eat whole such as strawberries. Maximize the vitamin C your citrus fruits retain by waiting to peel the fruit until just before you eat them. Not only will they keep more of their vitamin C, they'll also have a fresher flavor.

Time

Even your best efforts at preserving this ephemeral vitamin cannot stop some losses due to time. The same processes that cause accelerated vitamin C loss -- leaching into water and oxidation due to light and heat -- occur at cooler temperatures too, albeit more slowly. Because vitamin C naturally leaves fruits and vegetables over time, picking produce that has spent less time in transit typically has a higher vitamin C content. Whenever possible, buy local produce to minimize the time from farm to table. Frozen foods can also preserve larger quantities of vitamin C because manufacturers freeze them so quickly that they retain the nutritional value of the fruit in peak condition.