Determination of free glutamic acid in a variety of foods by high-performance liquid chromatography.

A survey of free glutamic acid levels in a variety of foods was conducted. The foods were analysed by high-performance liquid chromatography (HPLC). Free glutamic acid was extracted from the food with 0.02 M potassium phosphate with subsequent precipitation of other food components with acetone. Impurities were removed by passing the extract through a C-8 or C-18 reversed-phase solid-phase extraction column. The free glutamic acid was derivatized with phenylisothiocyanate, and the derivative was separated by HPLC with detection at 254 nm. Free glutamic acid levels ranged from not found (< 20 ppm) in some spices to as high as 89% in another spice.