Abstract
Ascorbic dehydroascorbic and diketogulonic acids in daily meals before and after cooking were respectively determined by the dinitrophenylhydrazine method.
The color of the extract of the cooked meals was bleached by charcoal in trichloroacetic acid solution.This procedure could make change also ascorbic acid into dehydroascorbic acid. Therefore, the value of ascorbic acid was the difference between total ascorbic acid and dehydroascorbic acid. The true values of dehydroascorbic acid could be obtained when the samples were treated with 2% SnCl2 in 5% metaphosphoric acid solution.
By the above method the percentages of each fraction of Vitamin C and an available Vitamin C in cooked meals upon that of the uncooked foods were estimated as follows:
Ascorbic acidaround 60%
Dehydroascorbic acid "180%
Diketogulonic acid " 160%
Available Vitamin C " 75%
However, it was observed that real intake of an available Vitamin C from cooked meals was around 50% upon the calculated values of Vitamin C in daily meals.
