Enzymatic methods in food analysis: determination of ascorbic acid.

The feasibility and expediency of enzymatic methods application in food analysis is demonstrated by the example of ascorbic acid (AsA) determination in foods. Enzymatic determination of ascorbic acid is based on its action as a second substrate of horseradish (HRP) and peanut (PNP) peroxidases in the reactions of o-dianisidine (OD) and 3,3',5,5'-tetramethylbenzidine (TMB) oxidation with hydrogen peroxide. The rates of the reactions are monitored spectrophotometrically by measuring the duration of the induction period on kinetic curves plotted in coordinates absorption-time. The proposed procedures are sensitive (c(L)=0.1 microM), simple, and rapid. The procedure using horseradish peroxidase and the reaction of TMB oxidation was used to determine ascorbic acid in fruit juices, milk and sour-milk products for babies' nutrition.