Flavour enhancers are additives added to food to intensify its flavour and/or aroma, either by amplifying a specific taste or by enhancing the overall perception of all flavour characteristics. However, flavour enhancers themselves do not impart any flavour or odour to food.[1][2]
Like other food additives, they are identified by their name and/or a code number in the E numbering system, where “E” stands for Europe. Flavour enhancers are listed under the range E620–E650.[3]
Almost all flavour enhancers authorised for use in the European Union fall into three main groups or classes: glutamates, inosinates, and guanylates. Among these, the most commonly used are monosodium glutamate (E621), disodium inosinate (E631), and disodium guanylate (E627).[4]
Based on currently available scientific evidence, flavour enhancers, when used in accordance with established guidelines, do not pose a risk to human health.[5][6]
Contents
Glutamates
Glutamates include glutamic acid (E620), one of the amino acids that make up proteins, and its sodium, potassium, calcium, and ammonium salts. These molecules enhance the umami taste in food, considered the fifth basic flavour perceived by humans, alongside salty, sweet, bitter, and sour. Umami is often described as similar to the taste of meat broth.[7][8]
Glutamates are numbered from E620 to E625.
Monosodium glutamate, the sodium salt of glutamic acid, was the first flavour enhancer to be used industrially and remains the most widely used among glutamates. It is commonly added to foods such as soups, savoury snacks, and sauces to induce the umami taste. On ingredient labels, it may also appear under names such as sodium glutamate, glutamic acid monohydrate, vetsin, Ajinomoto, or monosodium L-glutamate.[2][9]
Inosinates
Inosinates include inosine monophosphate (IMP) or inosinic acid (E630), one of the nucleotides involved in the synthesis of DNA and RNA, and its sodium, potassium, and calcium salts. Like glutamates, they act as flavour enhancers by intensifying the umami taste.[4]
They are approximately ten times more potent than glutamates and are numbered from E630 to E633.
The most widely used inosinate is disodium inosinate, which is frequently combined with disodium guanylate to form a mixture known as disodium 5′-ribonucleotides (E635).[7][8][10]
Guanylates
Guanylates include guanosine monophosphate (GMP) or guanylic acid (E626), one of the nucleotides involved in the synthesis of RNA and DNA, and its calcium, potassium, and sodium salts. Unlike glutamates and inosinates, guanylates do not impart an umami taste themselves but are capable of strongly enhancing a wide range of other flavours.[4]
They are numbered from E626 to E629.[10]
The most widely used guanylate is disodium guanylate (E627). Due to its relatively high cost, it is generally used in combination with monosodium glutamate or disodium inosinate.[7][8]
Examples of flavour enhancers
The following is a review of the flavour enhancers listed among the food additives authorised in the European Union under Commission Regulation (EU) No 1129/2011, adopted on 11 November 2011. This regulation amended Annex II of Regulation (EC) No 1333/2008 of the European Parliament, and was itself subsequently amended in 2013.[1]
| E-number | Additive class and derivatives |
|---|---|
| Glutamates | |
| E620 | Glutamic acid |
| E621 | Monosodium glutamate |
| E622 | Monopotassium glutamate |
| E623 | Calcium diglutamate |
| E624 | Monoammonium glutamate |
| E625 | Magnesium diglutamate |
| Guanylates | |
| E626 | Guanylic acid |
| E627 | Disodium guanylate |
| E628 | Dipotassium guanylate |
| E629 | Calcium guanylate |
| Inosinates | |
| E630 | Inosinic acid |
| E631 | Disodium inosinate |
| E632 | Dipotassium inosinate |
| E633 | Calcium inosinate |
| Other compounds | |
| E634 | Calcium 5′-ribonucleotides |
| E635 | Disodium 5′-ribonucleotides |
| E640 | Glycine and its sodium salt |
| E650 | Zinc acetate |
Health effects
For many years, monosodium glutamate was thought to cause allergic reactions and food intolerances, often referred to as the “Chinese restaurant syndrome.” However, based on numerous studies, the scientific community has established that this flavour enhancer, when consumed in authorised amounts, is safe for consumers, including children.[10][11]
Although the purine moiety of inosinates and guanylates is metabolised into uric acid, which plays a role in the development of gout, the quantities ingested from flavour enhancers are negligible compared with those naturally present in foods. Therefore, their contribution to gout development appears to be insignificant.[12]
More broadly, studies on flavour enhancers have found no evidence of adverse effects on reproduction, carcinogenicity, or teratogenicity.[6]
It can therefore be concluded that, when used in accordance with established guidelines, flavour enhancers are not harmful to human health.[13]
References
- ^ a b Commission Regulation (EU) No 1129/2011 of 11 November 2011 amending Annex II to Regulation (EC) No 1333/2008 of the European Parliament and of the Council by establishing a Union list of food additives. https://eur-lex.europa.eu/eli/reg/2011/1129/2013-11-21
- ^ a b European Union. Guidance notes on the classification of a flavouring substance with modifying properties and a flavour enhancer. 27 May 2014. https://food.ec.europa.eu/system/files/2016-10/fs_food-improvement-agents_flavourings-guidance_modifying_properties.pdf
- ^ Food Standards Agency. Approved additives and E Numbers. Last updated: 16 July 2025.
- ^ a b c Yamamoto T., Inui-Yamamoto C. The flavor-enhancing action of glutamate and its mechanism involving the notion of kokumi. NPJ Sci Food 2023;7(1):3. doi:10.1038/s41538-023-00178-2
- ^ Zanfirescu A., Ungurianu A., Tsatsakis A.M., Nițulescu G.M., Kouretas D., Veskoukis A., Tsoukalas D., Engin A.B., Aschner M., Margină D. A review of the alleged health hazards of monosodium glutamate. Compr Rev Food Sci Food Saf 2019;18(4):1111-1134. doi:10.1111/1541-4337.12448
- ^ a b Ekelman K. and Raffaele K.C. Disodium 5′-guanylate and disodium 5′-inosinate. Additives evaluation branch, division of health effects evaluation. Center for food safety and applied nutrition. Food and Drug Administration, Washington, DC, USA.
- ^ a b c Briand L. and Salles C. 4 – Taste perception and integration. Editor: Etievant P., Guichard E., Salles C. and Voilley A. Booktitle: Flavor. Woodhead Publishing. 2016;101-119. doi:10.1016/B978-0-08-100295-7.00004-9
- ^ a b c Nelson D.L., Cox M.M. Lehninger. Principles of biochemistry. 8th Edition. W.H. Freeman and Company, 2021.
- ^ Moldovan O.L., Rusu A., Tanase C., Vari C.E. Glutamate – A multifaceted molecule: Endogenous neurotransmitter, controversial food additive, design compound for anti-cancer drugs. A critical appraisal. Food Chem Toxicol 2021;153:112290. doi:10.1016/j.fct.2021.112290
- ^ a b c EFSA. Call for data for the re-evaluation of ribonucleotides (E 626-635) as food additives. 28 June 2023.
- ^ Geha R.S., Beiser A., Ren C., Patterson R., Greenberger P.A., Grammer L.C., Ditto A.M., Harris K.E., Shaughnessy M.A., Yarnold P.R., Corren J., Saxon A. Multicenter, double-blind, placebo-controlled, multiple-challenge evaluation of reported reactions to monosodium glutamate. J Allergy Clin Immunol 2000;106(5):973-80. doi:10.1067/mai.2000.110794
- ^ Brulé D., Sarwar G., Savoie L., Campbell J., Van Zeggelaar M. Differences in uricogenic effects of dietary purine bases, nucleosides and nucleotides in rats. J Nutr 1988;118(6):780-6. doi:10.1093/jn/118.6.780
- ^ EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS); Mortensen A., Aguilar F., Crebelli R., et al. Re-evaluation of glutamic acid (E 620), sodium glutamate (E 621), potassium glutamate (E 622), calcium glutamate (E 623), ammonium glutamate (E 624) and magnesium glutamate (E 625) as food additives. EFSA J 2017;15(7):e04910. doi:10.2903/j.efsa.2017.4910