Ascorbate oxidase from starfruit (Averrhoa carambola): preparation and itsapplication in the determination of ascorbic acid from fruit juices

A study was conducted to utilize ascorbate oxidase (AAO) from very immature starfruit for the enzymatic determination of ascorbic acid (AsA) in colore d samples. The enzyme preparation was carried out by a combination of (NH4) (2)SO4 fractionation, DEAE-Toyopearl 650 M and ultrafiltration. A calibrati on curve for AsA was constructed by plotting the amount of AsA oxidized by the enzyme at a specified reaction time against the absorbance. The curve s howed a linear relationship in the range of 0-100 mu g ml(-1) AsA used. Usi ng the plot, the values of AsA in juice samples were determined and compare d with the conventional 2,6-dichloroindophenol method. (C) 1999 Elsevier Sc ience Ltd. All rights reserved.