A survey on the presence of free glutamic acid in foodstuffs, with and without added monosodium glutamate Tiziana Populin, Sabrina Moret * , Simone Truant, Lanfranco S. Conte Department of Food Science, University of Udine, Via Marangoni 97, 33100 Udine, Italy Received 12 September 2006; received in revised form 30 December 2006; accepted 14 March 2007 Abstract 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. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: MSG; Glutamic acid; Biogenic amines; Free amino acids; HPLC 1. Introduction L-Glutamic acid (Glu) is a widespread amino acid pres- ent in foodstuffs as the free and protein-bound form. Foods containing large amounts of free Glu (tomatoes, mush- rooms and cheese) are traditionally used to obtain savoury dishes (Giacometti, 1979; Yamaguchi & Ninomiya, 2000). Only the free form of Glu, in its L-configuration, presents flavour enhancing properties, and, for this reason, it is widely used as a flavour enhancer in the food industry, par- ticularly in the form of the monosodium salt. Monosodium glutamate (MSG) gives the typical aroma ‘‘umami”, recog- nized as the fifth basic taste, very similar to ‘‘meat aroma” or ‘‘broth aroma” (Bellisle, 1999). MSG can be added ‘‘pure” or as a ‘‘hidden ingredient” of yeast extracts or hydrolyzed proteins, both containing high percentages of Glu (Hegenbart, 1998; Nagodawithana, 1992). There is no complete agreement about the safety of MSG, even though the Food and Drug Administration (FDA) includes it among the substances generally recog- nized as safe (GRAS). A report from the Federation of American Societies for Experimental Biology (FASEB, 1995), identified two groups of people susceptible to high MSG doses: a group intolerant to high quantities of MSG and asthmatics. Even though MSG has been identi- fied as a determining factor of ‘‘Chinese restaurant syn- drome” and migraine (Bader, 1992; Rajda, Tajti, Komoro ´ czy, Seres, & Klive ´nyi, 1998; Schwartz, 1988; WHO, 1987), properly conducted double-blind studies among individuals who claimed to suffer from the syn- drome, have failed to demonstrate an unequivocal relation- ship between ‘‘Chinese restaurant syndrome” and MSG consumption (Geha et al., 2000; WHO, 1987). 0308-8146/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2007.03.034 * Corresponding author. Tel.: +39 0432 590725; fax: +39 0432 590719. E-mail address: sabrina.moret@uniud.it (S. Moret). www.elsevier.com/locate/foodchem Food Chemistry 104 (2007) 1712–1717 Food Chemistry