An optical fiber chemical sensor for the determination of free glutamate in food samples was fabricated based on the
immobilization of 0.1 M copper(II) nitrate trihydrate onto sol-gel glass powder which was then mixed with methyl cellulose
to form a pellet. A distinctive colour change from light blue to dark blue was observed in the presence of glutamate in
less than 1 min. The colour change was measured by reflectance spectrophotometer at 691 nm. A linear relationship
between the reflectance intensity and glutamate concentration was observed in the range of 12.5 to 500 mM with a limit
of detection of 10.6 mM. This method is also reproducible with a relative standard deviation of less than 5%, no effect on
pH of the glutamate solution and a good recovery of above 80%. The sensor was used for the determination of glutamate
in common food items such as soups and flavor enhancers. The results obtained from the fabricated sensor were found
to be comparable with HPLC method.