Why does this happend to fruits and vegetables with vitamin C in them?

Most of the fruits and vegetables that contain vitamin C will rapidly lose the vitamin to the surrounding air.

Why does this happend to fruits and vegetables with vitamin C in them?
It's called oxidation. Oxygen in air reacts with vitamin C
Reply:L-Ascorbic acid (Vitamin C) is oxidized to L-Dehydroascorbic acid.





However this reaction is not "rapid" in most fruits. Orange juice and tomato juice, for example, lose Vitamin C only slowly. The Vitamin C level indicated on the nutritional label of refrigerated orange juice is the level "when consumed" and many refrigerated orange juice products have 45 or more days "use by dates".