The human body produces its own glutamate for a number of essential functions. Glutamate is not only taken in with our food supply but is also synthesized by our bodies.
Glutamate was first identified more than 100 years ago by the German chemist Heinrich Ritthausen, but it was Professor Kikunae Ikeda of Tokyo Imperial University who in 1908 realized for the first time that glutamate gave foods a unique taste and named this taste “Umami,” the fifth basic taste after sweet, salty, sour and bitter.
After isolating glutamate as the source of umami taste from the traditional Japanese kelp (seaweed) broth, Ikeda invented a method to isolate glutamate from wheat protein called gluten. He tested many different glutamate salts such as sodium, calcium, potassium, but the one that was more stable and had clear umami taste was sodium glutamate. This is how the umami seasoning monosodium glutamate (MSG) was born. Mono meaning one, monosodium glutamate refers to the salt of glutamate that contains only one molecule of sodium. Today, MSG is made by the fermentation of starches such as sugar cane or molasses and does not contain gluten.
Glutamate is also commonly found in many umami rich foods, such as tomatoes, cheese, meats, and many fermented soy and fish sauces. Hence, although the classification of umami as a basic taste is a recent development, fermented fish products, such as nam pla in Thailand and nuoc mum in Vietnam and other Southeast Asian countries, have been used traditionally to enhance the flavor and add umami to dishes. The level of free glutamate in these fermented fish products is as high as Parmesan cheese.
People have actually been familiar with umami for centuries (without recognizing the term), as a part of the stocks or bouillon in Europe, tomato sauce and cheese in Italy and Greece, fish sauce called “Garum” in ancient Rome, and soy sauce in Southeastern Asian countries.
Umami and Food Palatability
Shizuko Yamaguchi and Kumiko Ninomiya
Journal of Nutrition. 2000;130:921S-926S.
Faculty of Applied Bioscience, Department of Nutritional Science, Tokyo University of Agriculture and Technical Committee, Umami Manufacturers Association of Japan, Tokyo, Japan
Umami is the term that identifies the taste of substances such as L-glutamate salts, which were discovered by Ikeda in 1908. Umami is an important taste element in natural foods; it is the main taste in the Japanese stock “dashi,” and in bouillon and other stocks in the West. The umami taste has characteristic qualities that differentiate it from other tastes, including a taste-enhancing synergism between two umami compounds, L-glutamate and 5′-ribonulceotides, and a prolonged aftertaste. The key qualitative and quantitative features of umami are reviewed in this paper. The continued study of the umami taste will help to further our general understanding of the taste process and improve our knowledge of how the taste properties of foods contribute to appropriate food selection and good nutrition.
Glutamate is not only taken in with our food supply but is also synthesized by our bodies. From a nutritional perspective, glutamate is a non-essential amino acid. Most dietary glutamate is rapidly metabolized in the gut and is used as an energy source. This paper shows that the body produces its own glutamate for a number of essential functions.
Intestinal Glutamate Metabolism
Peter J. Reeds, Douglas G. Burrin, Barbara Stoll and Farook Jahoor
U.S. Department of Agriculture/Agricultural Research Service, Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX
Journal of Nutrition. 2000;130:978S-982S.
Although it is well known that the intestinal tract has a high metabolic rate, the substrates that are used to generate the necessary energy remain poorly established, especially in fed animals. Under fed conditions, the quantification of substrate used by the gut is complicated by the fact that potential oxidative precursors are supplied from both the diet and the arterial circulation. To circumvent this problem, and to approach the question of the compounds used to generate ATP in the gut, we combined measurements of portal nutrient balance with enteral and intravenous infusions of [U-13C]substrates. We studied rapidly growing piglets that were consuming diets based on whole-milk proteins. The results revealed that 95% of the dietary glutamate presented to the mucosa was metabolized in first pass and that of this, 50% was metabolized to CO2. Dietary glucose was oxidized to a very limited extent, and arterial glutamine supplied no >15% of the CO2 production by the portal-drained viscera. Glutamate was the single largest contributor to intestinal energy generation. The results also suggested that dietary glutamate appeared to be a specific precursor for the biosynthesis of glutathione, arginine and proline by the small intestinal mucosa. These studies imply that dietary glutamate has an important functional role in the gut. Furthermore, these functions are apparently different from those of arterial glutamine, the substrate that has received the most attention.