Determination of Amino Group Based on Glutaraldehyde and XTT: Its Application to Protein Determination in Food

Abstract

A rapid and convenient spectrophotometric method for determination of amino group was developed using the bifunctional reagent glutaraldehyde and water-soluble tetrazolium XTT. The method is based on the formation of XTT formazan by the reduction with dihydropyridine that generates in the reaction of glutaraldehyde with amino group. Only 5 min was required for an assay. The detection limit of lysine was 1 nmol/assay. When the method was applied to the determination of protein, the detection limit was 1.1 μg/assay for BSA. Satisfactory recovery data were obtained when casein was added to commercial milk (99–101%).