Free glutamate in foods: the source of taste and the signal of protein

Miro Smriga
European Committee for Umami
c/o: Ajinomoto Europe SAS, 153 rue de Courcelles, 75017 Paris, France
 miro_smriga@ehq.ajinomoto.com

Although the Japanese term umami, which stands for the fifth basic taste transmitted by free L-glutamate (Glu), may sound new to a Western ear, the use of the free Glu as a flavor enhancer in food has at least two thousand years of history. Romans, in their times fermented small fishes to break down proteins in order to obtain “fish sauces”, which contained high doses of Glu. These “fish sauces”, known in antique Rome as liquamen or garum(1), were widely spread throughout the Roman Empire and this “old technology” is still being used in South East Asia for fish sauce production. Most cultures use free amino acids to improve the sensory quality of food, and thus the popularity of ingredients with high doses of free Glu, such as Maggi cubes, Worchester sauce, tomato sauce, Parmesan cheese, or soy sauce attest to the global appeal of the Umami flavor.

Umami - along with sweetness - is a taste which human beings are predisposed to find pleasant. Umami can be combined with bitterness and saltiness to create a perfectly balanced combination of tastes.

Monosodium glutamate (MSG) is one of the main free Glu carriers. The intake of MSG added to foods varies among world regions, highest intakes being in Eastern Asia. While the intake of protein-bound Glu in typical Western diet ranges between 10 and 40 g/day/person, the intake of free Glu from MSG in Europe is lower than 1g/day/person. The reason for this mainly lays in the strong dose-dependency of the flavour effects of free Glu, which at higher dose is repelling. Due to this self-limiting property of free Glu and also for a well-developed compartmentalization of Glu within the body, the world regulatory authorities regard the carriers of free Glu (i.e., MSG) as a safe food additive/component for which acceptable daily intake (ADI) was not established.

Non-specified ADI means that the total daily intake of Glu, in levels necessary to achieve the desired taste effect and from its acceptable background in food, does not represent a hazard to health.  This conclusion has been supported by recent scientific data which documented Glu receptors not only on the tongue but also within the gastrointestinal tract, where they contribute to suitable metabolic use of dietary proteins and to the proper gastric functioning.

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