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July 28, 2003
Volume 81, Number 30
CENEAR 81 30 p.57
ISSN 0009-2347



Seasoning originally isolated from seaweeds boosts the flavor of many food products

A. Maureen Rouhi

The first cooking trick I ever picked up, when I was about eight years old, was to mix in a pinch of "vetsin" to any entrée just before it is to be served. This magic ingredient of pure white crystals made an enormous difference in flavor that even as a child I could discern. Years later, I learned what this "vetsin" stuff was: monosodium l-glutamate (MSG).

YUM-YUM Sold in the U.S. as Accent, monosodium l-glutamate is added to a variety of products.


MSG may be the most widely used flavor enhancer after salt and pepper. Annual worldwide demand is about 1.1 million tons, according to Leo Hepner, president of the U.K. consulting firm L. Hepner & Associates, which specializes in fermentations and biotechnology. About 70% of the demand comes from Pacific Basin countries. The rest comes from South America (about 15%) and Europe and North America (about 15%).

Most of the supply comes from companies based in Japan (Ajinomoto and Kyowa Hakko) and South Korea (Cheil Jedang), Hepner says. But in the past three years, Chinese companies have joined the ranks. Their entry, he says, makes it likely that the price of MSG--currently $1.30 per kg--will decrease considerably in the next few years.

MSG is produced by fermentation. Certain bacteria convert molasses or starch hydrolyzate to l-glutamic acid, which is neutralized with sodium hydroxide to form MSG. Before fermentation was adopted, the main source of l-glutamic acid was extraction from wheat gluten, which contains as much as 25% of the amino acid by weight.

The flavor-enhancing property of MSG was discovered in 1908 by Kikunae Ikeda, a chemistry professor at Imperial University of Tokyo and founder of Ajinomoto. He isolated the substance in a seaweed that for centuries Japanese cooks had been using to make food taste better and found that it was l-glutamate. MSG first came to market in 1909 under the trade name Aji-No-Moto. In the U.S., a popular brand is Accent.

Ikeda suggested that free l-glutamate elicits a taste that is distinct from the four known primary tastes: sour, sweet, salty, and bitter. He proposed calling this fifth taste "umami," after the Japanese word "umai," which means delicious. The best equivalent English word is "savory," as exemplified by protein-rich foods such as meats and cheeses. He reported the discovery and his hypothesis about a fifth taste in 1909 in the Journal of the Chemical Society of Tokyo. A translation of that paper was published just last year [Chem. Senses, 27, 847 (2002)].

Acceptance of umami as a basic taste came only decades after Ikeda laid out his hypothesis, after other umami substances were identified--inosine 5'-monophosphate (IMP) and guanosine 5'-monophosphate (GMP)--and taste responses were investigated in humans and animals. Identification of l-glutamate taste receptors in 2000 by researchers Nirupa Chaudhari and Stephen Roper at the University of Miami School of Medicine dispelled any lingering doubts.

On its own, MSG doesn't have much taste, but its effect is noticeable when added to soups, stews, and snacks, among other foods. Synergisms between MSG and IMP or GMP are known. Adding a pinch of MSG to food containing these nucleotides enhances the umami taste up to eight times the original. Food products claiming "No MSG" may contain disodium salts of IMP and GMP as alternative flavor enhancers.

Reports of adverse reactions to MSG, collectively called "Chinese restaurant syndrome," began surfacing in the late 1960s. Conditions ranging from chest pains to migraine headaches were blamed on MSG. For a while, signs proclaiming "No MSG added" in Asian restaurants were inescapable as MSG suffered the bad rap.

No credible studies substantiate any harmful health effects caused by MSG, according to Lisa Katic, director of public affairs for the Glutamate Association, an organization of manufacturers, national marketers, and processed food users of MSG. "We go by what organizations like the [Food & Drug Administration] communicate to the public, which is that MSG is safe and that there are no ill health effects from consuming food containing MSG."

The toxicology of MSG has been studied extensively, and its safety has been affirmed by organizations other than FDA. l-Glutamic acid is one of the 20 amino acids that make up natural proteins. The World Health Organization and the Food & Agricultural Organization both have established the acceptable daily intake for l-glutamic acid and its salts as "not specified."

This means that, on the basis of available data and the amount needed to achieve the desired effect, a numerical limit for daily intake is not necessary. According to the Glutamate Association, such a classification is the safest category for a food additive.

In the U.S., any food product to which MSG is added must include it in the ingredient list. But the absence of MSG in the ingredient list does not mean that the product has no free l-glutamate, because many foods contain it naturally, including milk, eggs, potatoes, tomatoes, mushrooms, walnuts, and cheese. Also, free l-glutamate can be introduced into products through hydrolyzed proteins. If hydrolyzed proteins are in the ingredients list, the product cannot make a "no MSG added" claim, according to FDA.

The bad rap about MSG seems to have faded. "That's because good and credible information has gotten out to the public," Katic says. "The science has reiterated MSG's safety, the safety has been communicated efficiently, and the public is confident that this food ingredient is safe."

Back in my kitchen, I haven't used free-flowing, pure, white crystal MSG for years. But I do use bouillon cubes regularly. When I checked the ingredients, indeed, they include MSG.


Related Stories
Taste receptor for amino acids
[C&EN, March 4, 2002]

[C&EN, September 10, 2001]

[C&EN Archive]

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