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Can you please explain to me the process occurring when oranges are damaged causing the concentration of vitamin C to decrease.
Igloo writes ...
Vitamin C (ascorbic acid) can be oxidised by oxygen in the air to form dehydroascorbic acid. Look for standard diagrams of these two structures.
At room temperature and in the absence of enzyme catalysts, this process is fairly slow, and vitamin C can be regarded as being fairly stable, especially in acidic conditions, which is how it is found in most fruit.
However, the redox process above rapidly accelerates in the presence of the enzyme ascorbic acid oxidase, and, as I have described in a previous answer, fruit damage causes the plant cells to rupture allowing this enzyme to mix freely with the fruit juice. So, as a result, the concentration of vitamin C falls fairly rapidly.
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updated: 26 September 2007
