Methods for Determining L-Glutamate in Soy Sauce with L-Glutamate Oxidase

Abstract

L-Glutamate in soy sauce was determined with L-glutamate oxidase partially purified from the aqueous extract of a wheat bran culture of Streptomyces sp. X-l 19-6. L-Glutamate was determined spectrophotometrically by measuring a-ketoglutarate or hydrogen peroxide with a good correlation coefficient with conventional autoanalyzer analysis with L-glutamate decarboxylase. The value obtained by hydrogen peroxide method indicated 85% of that of conventional method. L-Glutamate was also determined electrically by monitoring oxygen consumption of the enzymereaction mixture. This method is very simple and rapid but spend a large amount of enzyme.