Determination of Vitamin C (L‐ascorbic Acid and Dehydroascorbic Acid) in Food by Manual and Automated Photometric Methods

Abstract

L-ascorbic acid (AA) plus dehydroascorbic acid (DHAA) in foods were determined manually and with an automated sample processor according to the principles of the 2,4-dinitrophenylhydrazine method of Pelletier [J. Lab. & Clin. Med. (1968), 72: 6741 for biological materials but with modifications that rendered the methods simpler and applicable to foods. These methods eliminated interference from reductones (arising from sugars during food processing) and of diketogulonic acid (a product of the oxidation of DHAA). Sucrose in a concentration 30,000 times that of AA did not affect the vitamin C assay values. Fructose and glucose, in concentrations respectively 417 and 1668 times that of AA, increased the vitamin C values by only 2-3%. Since a higher range of concentrations of fructose and glucose together gave rather constant increase (8%) in vitamin C values, possible interference from the sugars in noncitrus fruits was eliminated by incorporating a mixture of these sugars in the solutions of standards and samples. Comparisons of vitamin C values in food between the proposed procedures and a modification of the widely used method of Roe [J. Biol. Chem. (1961b) 236: 16111 showed agreement (?5%) for 70% of the foods analyzed. Values were approximately 10% lower by the proposed procedures in the remaining samples. These differences were attributed to the greater specificity of the new methods. Precision of the new procedures was generally within a coefficient of variation of 6% and values (mean of 4 assays on different days) obtained with an automatic sample processor and with manual analyses agreed within 3%.

Photometric Methods for the Determination of Vitamin C

“…The interference of sugars can be minimized by carrying out incubation at 15˚C and measuring the absorbance only after adding sulfuric acid for 75 min. 56 The use of several acid mixtures has been proposed for replacing the tedious dropwise addition of sulfuric acid. Lack of specificity is found with many of these methods; interfering osazones can be separated by chromatographic methods such as TLC 57 and HPLC 58 , but at the cost of making these procedures tedious and cumbersome.…”

Effects of pH Level of L-Ascorbic Acid Solution and Soaking at Various Growth Stages on the Leaf Exogenous Ascorbic Acid Content of Lettuce and Japanese Bunching Onion.

“…It has been reported that DHA is still effective in the physiological activity of vitamin C (Erdman and Klein,1982 ;Russel et al, 1983). Furthermore, it is considered that DHA has substantially the same activity as AsA in physiological activity (Pelletier and Brassard, 1977;Mokady et al ., 1984).…”

Electrochemical Determination of Ascorbic Acid and Isoascorbic Acid in Ground Meat and in Processed Foods by High Pressure Liquid Chromatography

“…Samples (3-5 g) were homogenized in a polytron in enough cold 17% (w/v) HPO 3 (J. T. Baker Inc., Phillipsbury, NJ) to give a final concentration of 0.85% (v/v) HPO 3 (Pelletier and Brassard, 1977). Homogenates were centrifuged at 30,000g in a refrigerated centrifuge 4ЊC for 30 min.…”