Investigations on The Stability and Determination of Dehydroascorbic Acid

Abstract

The time intervals for complete reduction of dehydroascorbic acid by H2S at pH 4, 5, 6, and 7 at temps. of 0[degree], 25[degree], and 40[degree]C have been determined. The times are given for half destruction of dehydroascorbic acid at pH 0, 1, 2.2, 3, 4, 5, 6, and 7 at temps. of 0[degree], 25[degree], 40[degree], 70[degree], and 100[degree]C. The rate of destruction is least at pH 2.2. Borate considerably accelerates the destruction of dehydroascorbic acid, particularly at higher pH. A procedure is described which increases the specificity of the detn. of dehydroascorbic acid by in-dophenol titration. This involves extraction at pH 2, reduction with H2S at pH 5.3, and destruction of dehydroascorbic acid with borate to obtain a blank. This blank is considerable in extracts from a number of fruit and vegetable products. Little dehydroascorbic acid was found in most of the fresh fruits and vegetables and in the processed juices examined, but appreciable concns. were found in the fresh juices.