Monosodium [mon-uh-soh-dee-uhmglutamate [gloo-tuh-meyt] (MSG) is a seasoning salt and one of the most abundant naturally occurring non-essential amino acids. The glutamate of MSG confers the same umami (savory) taste of glutamate from other foods (e.g. meats, poultry, fish, eggs, dairy products, and kombu seaweed), being chemically identical.

Industrial food manufacturers market and use MSG as a flavor enhancer because it balances, blends and rounds the total perception of other tastes. Professor Kikunae Ikeda from the Tokyo Imperial University isolated glutamic acid as a new taste substance in 1908 from kombu, and named its taste ‘umami.’

He noticed that the Japanese broth of bonito fish flakes and kombu had a peculiar taste that had not been scientifically described at that time and was differed from sweet, salty, sour, and bitter. To verify that ionized glutamate was responsible for the umami taste, Professor Ikeda studied the taste properties of many glutamate salts such as calcium, potassium, ammonium, and magnesium glutamate.

All salts elicited umami in addition to a certain metallic taste due to the other minerals. Among those salts, sodium glutamate was the most soluble and palatable, and crystallized easily. Professor Ikeda named this product monosodium glutamate and submitted a patent to produce MSG. Suzuki brothers started the commercial production of MSG in 1909 as Aji-no-moto, meaning ‘essence of taste’ in Japanese, the first time that monosodium glutamate was manufactured.

MSG has been used safely for more than 100 years to season food. During this period, extensive studies were conducted to elucidate the role, benefits and safety of MSG. At this point, international and national bodies for the safety of food additives consider MSG safe for human consumption as a flavor enhancer.

The ‘MSG symptom complex’ was originally termed as the ‘Chinese Restaurant Syndrome’ when anecdotally Dr. Robert Ho Man Kwok reported the symptoms he felt after an American-Chinese meal to the New England Journal of Medicine. Kwok suggested multiple reasons behind the symptoms, including alcohol from cooking with wine, the sodium content, or the MSG seasoning. But MSG became the focus and the symptoms have been associated with MSG ever since. A controlled double-blind multicenter clinical trial failed to demonstrate the relationship between MSG Symptom complex and the consumption of MSG in individuals that believed to react adversely against MSG.

Pure MSG does not have a pleasant taste until it is combined with a consonant savory smell. As a flavor and in the right amount, MSG can enhance other taste-active compounds, improving the overall taste of certain foods. MSG mixes well with meat, fish, poultry, many vegetables, sauces, soups, and marinades, and increases the overall preference of certain foods like beef consommé. But like other basic tastes (except sucrose), MSG improves the pleasantness only in the right concentration: an excess of MSG is unpleasant. The optimum concentration varies with the type of food; in clear soup, the pleasantness score rapidly falls with more than 1 g of MSG per 100 ml.

There is also an interaction between MSG and table salt (sodium chloride), and other umami substances such as nucleotides. With these properties, MSG can be used to reduce salt intake (sodium), which predisposes to hypertension, heart diseases, and stroke. The taste of low-salt foods improves with MSG even with a 30% salt reduction. The sodium content (in mass percent) of MSG is roughly 3 times lower (12%) than in sodium chloride (39%).

MSG is one of several forms of glutamic acid found in foods, in large part because glutamic acid, being an amino acid, is pervasive in nature. Glutamic acid and its salts can also be present in a wide variety of other additives, including hydrolyzed vegetable protein, autolyzed yeast, hydrolyzed yeast, yeast extract, soy extracts, and protein isolate, which must be labeled with these common and usual names.

Since 1998, MSG cannot be included in the term ‘spices and flavorings.’ However, the term ‘natural flavor’ is now used by the food industry when using glutamic acid (which is similar to MSG, lacking only the sodium ions). Due to lack of FDA regulation, it is impossible to determine what percentage of ‘natural flavor’ is actually glutamic acid. The FDA considers labels such as ‘No MSG’ or ‘No Added MSG’ to be misleading if the food contains ingredients that are sources of free glutamate, such as hydrolyzed protein. In 1993, the FDA proposed adding the phrase ‘(contains glutamate)’ to the common or usual names of certain protein hydrolysates that contain substantial amounts of glutamate.

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