A survey on the presence of free glutamic acid in foodstuffs, with and without added monosodium glutamate

A survey on free glutamic acid (Glu) content in a variety of foods (broths, soups, sauces and salad dressings), with and without added monosodium glutamate (MSG), was carried out. A simple procedure, involving a dilution step for liquid samples or homogenization with 0.1 N HCl for solid and slurry samples, followed by derivatization with o-phthaldialdehyde, HPLC separation on C18 column and spectrofluorometric detection, was employed to quantify Glu, as well as a number of other free amino acids and biogenic amines. Broths and soups with added MSG had Glu contents of 92.7–341 mg/100 g. The highest amounts of Glu in foods with no added MSG were found in products containing hydrolyzed proteins (up to 129 mg/100 g). None of the products ready for consumption exceeded the limit of 10 g/kg of food, established by the European Directive, 95/2/CE [European Parliament and Council Directive (1995). No. 95/2/EC of 20 February 1995 on food additives other than colours and sweeteners. Official Journal, L061, 1–40].Relatively high amounts of biogenic amines were found in marmite (77.3 mg/100 g of putrescine and 32.2 mg/100 g of tyramine) and soy sauce while broths and soups showed generally low amounts of biogenic amines, putrescine being the most represented.