Develop Amperometric biosensor for determining MSG levels in liquid foods.

Determining the existence of L-glutamate in both clinical and food samples is important. It is a neuroexcitory amino acid linked to several behavior patterns. It is a common food additive in the form of monosodium glutamate (MSG), and is linked with "Chinese restaurant syndrome."

A highly sensitive and stable L-glutamate sensor would be useful if it could rapidly detect MSG. With this objective in mind, Taiwanese scientists set out to develop a compact, portable sensing system using an L-GLOx modified biosensor, which can be applied to quantitatively determine the levels of MSG in liquid foods. The investigators used a screen-printed carbon electrode deposited with palladium as the basis of their research. To fabricate the sensor, polyvinyl alcohol functionalized with methyl pyridinium methyl sulfate (PVA-SbQ) containing a layer of l-glutamate oxidase (L-GLOx) was formed on the electrode.

To improve the sensitivity and reproducibility of the sensor, the scientists evaluated different types of immobilized layers. Amperometric biosensors function by the production of a current when a potential is applied between two electrodes. Amperometric measurements were performed using a laboratory-built potentiostat. Samples, spiked with various concentrations of standard solutions, were analyzed.

The scientists used the difference between the baseline and the steady-state current to calculate various concentrations of MSG. Recovery was determined by comparing the amount of MSG added with the amount of MSG detected. The sensor achieved a fast, sensitive response to change in the concentration of MSG.

The enzyme electrode exhibited a linear calibration range when determining different concentrations of MSG in a range from 50 nM to 100 nM and a correlation coefficient of 0.997. The detection limit of MSG was 50 nM. No significant difference was found in the response to 10 nM MSG over the course of 100 tests. Based on these results, the scientists believe that their electrochemical biosensor is sensitive enough and can be reproduced to detect MSG. The sensor could be a useful tool for detecting MSG in liquid foods.

Further information. Chuan-Liang Hsu, Department of Food Science, Yuanpei University, No. 306 Yuanpei St., Hsinchu City, Taiwan; phone: +886-3-5381183; fax: +886-3-5381183; fax: +886-3-6102342; email: clhsu@mail.ypu.edu.tw.