Kinetic-potentiometric determination of monosodium glutamate in soups and soup bases and of glutamic dehydrogenase

Abstract

A simple and selective procedure has been developed for the determination of glutamic acid and glutamic dehydrogenase by using an ammonia gas-sensing electrode. Glutamic acid is deaminated by bacterial glutamic dehydrogenase in the presence of β-NAD⁺. A linear relationship exists between the initial rate of ammonia release and the substrate concentration or the enzyme activity. Optimum conditions for the determinations were established. Glutamic acid in the range 1.0 × 10^–4–1.0 × 10^–3M and enzyme in the range 0.0500–0.750 U can be determined with relative errors of about 2%. A method is given for determining monosodium glutamate in soups and soup bases. The method was compared with the official AOAC method; satisfactory agreement was achieved.