Accurate glutamate monitoring in foodstuffs by a sensitive and interference-free amperometric biosensor

L-Glutamate (Glu) is a well-known flavour enhancer that is present in several foodstuffs either as an additive or a natural compound. Glu monitoring is an important issue since the excessive intake of this flavour enhancer can cause allergic and neurotoxic effects. Glu is currently determined by chromatographic or capillary electrophoretic methods, which require extensive sample pre-treatment and expensive equipments. A suitable alternative is represented by amperometric biosensors, low cost devices that could provide specific, rapid and repetitive analyses of complex matrices. In the last decade a number of biosensors for glutamate detection have been proposed, but the above mentioned requirements have not been completely met. In order to face these problems a proper selection of the electrode material and the use of permselective films are required. This work describes the development and optimization of an amperometric biosensor for glutamate monitoring in foodstuffs. The biosensor is based on glutamate oxidase (GLOD) immobilized by a gel of bovine serum albumine and glutharaldeyde onto a platinum electrode modified with a permselective overoxidized polypyrrole film. Different experimental conditions have been tested for the enzyme immobilization, and the optimized biosensor, integrated in a flow injection system, has been characterized in terms of linearity, LOD, LOQ, repeatability and stability of response. The excellent anti-interference characteristics towards the main interferents present in real food matrices have allowed the application of the biosensor in the accurate monitoring of Glu in different kind of foodstuffs.