Food Application of Newly Developed Handy-type Glutamate Sensor

Tests on physiological functions of umami have been actively conducted and a need recognized for a high-performance quantification device that is simple and cost-effective, and whose use is not limited to a particular location or user. To address this need, Ajinomoto Co. and Tanita Corp. have jointly been researching and developing a simple device for glutamate measurement. The device uses L-glutamate oxidase immobilized on a hydrogen peroxide electrode. L-glutamate in the sample is converted to α-ketoglutaric acid, which produces hydrogen peroxide. Subsequently, the electrical current from the electrochemical reaction of hydrogen peroxide is measured to determine the L-glutamate concentration. In order to evaluate its basic performance, we used this device to measure the concentration of L-glutamate standard solutions. In a concentration range of 0-1.0%, the difference from the theoretical value was minimal. The coefficient of variation (CV) value of 3 measurements was 4% or less. This shows that the device has a reasonable level of precision and accuracy. The device was also used in trial measurements of L-glutamate concentrations in food. There was a good correlation between the results obtained using the developed device and those obtained with an amino acid analyzer; the correlation coefficient was R=0.997 (n=24). In this review, we demonstrate the use of our device to measure the glutamate concentration in miso soup served daily at a home for elderly people, and other foods and ingredients.