Monosodium glutamate

• 1. Introduction

  ›

  Monosodium glutamate, known as MSG, is a sodium salt of glutamic acid, and on its own it is reported to taste highly unpleasant. It only comes alive when paired with a savory aroma. That strange behavior sits at the heart of a seasoning found in stock cubes, soups, ramen, gravy, stews, condiments and savory snacks. It also sits behind one of the most argued-over reputations in the kitchen. Where did this white powder come from, and who first isolated it? How did its production change across more than a century, from acid and wheat to bacteria and molasses? And why does a popular belief about headaches persist when carefully blinded studies keep failing to find the effect? Those questions run through the story ahead.

  583912

• 2. Ikeda and the Broth

  ›

  In 1866, the German chemist Karl Heinrich Ritthausen treated wheat gluten with sulfuric acid and identified a new compound. It took its name, glutamic acid, from the gluten it came from. Nobody yet knew what it tasted like in any useful sense.

  About four decades later, Kikunae Ikeda of Tokyo Imperial University was puzzling over dashi, the Japanese broth made from katsuobushi and kombu. He felt it carried a unique taste that science had not yet described. It was not sweet, salty, sour or bitter.

  In 1908, Ikeda isolated glutamic acid from the seaweed Laminaria japonica, the kombu of the broth, using aqueous extraction and crystallization. He named the taste umami, which means delicious taste.

  To find which form of glutamate would deliver that flavor best, Ikeda tested the taste of many glutamate salts, including calcium, potassium, ammonium and magnesium. Monosodium glutamate won on three counts. It was the most soluble, the most palatable and the easiest to crystallize.

  Ikeda called his product monosodium glutamate and submitted a patent to produce it. In 1909, the Suzuki brothers began commercial production under the name Ajinomoto, meaning essence of taste. Their first factory batches opened a production story with three very different methods.

  539414243

• 3. Three Ways to Make It

  ›

  For the first stretch of its commercial life, from 1909 to 1962, MSG came from acid. Makers boiled vegetable protein in hydrochloric acid to break its peptide bonds. Wheat gluten was the original raw material, because it holds more than 30 g of glutamate and glutamine in every 100 g of protein.

  Demand kept climbing, and chemists began studying other routes. The polyacrylic fiber industry had started in Japan in the mid-1950s, which made acrylonitrile a familiar industrial material. From 1962 to 1973, it served as the base for direct chemical synthesis of MSG.

  The current method is bacterial fermentation, and as of 2016 it supplies most of the world's MSG. The process resembles the making of vinegar or yogurt. Species of Corynebacterium are cultured with ammonia and carbohydrates from sugar beets, sugarcane, tapioca or molasses. The bacteria excrete amino acids into a culture broth, and L-glutamate is isolated from it.

  Sodium is added only later, to neutralize the product. Kyowa Hakko Kogyo, now called Kyowa Kirin, developed this industrial fermentation. Yields and production rates keep improving to match demand.

  Filtration, concentration, acidification and crystallization leave glutamate, sodium ions and water. That crystal has its own distinctive chemistry.

  433334444

• 4. Chemistry of the Crystal

  ›

  The finished compound usually appears as a monohydrate, a white, odorless, crystalline powder. In the solid, sodium cations and glutamate anions sit apart, with the glutamate in a zwitterionic form. Dropped into water, it dissociates into glutamate and sodium ions.

  MSG dissolves freely in water but is not hygroscopic. It will not dissolve in common organic solvents such as ether. It holds steady under ordinary food processing and does not break down during cooking.

  Like other amino acids, it will brown through the Maillard reaction when sugars are present at very high temperatures.

  The numbers on sodium are striking. MSG is 12.28 percent sodium by mass, while table salt is 39.34 percent. That puts MSG's sodium at about one-third of salt's, because the glutamate partner is so much heavier. The remaining 87.72 percent of MSG is glutamic acid.

  Cooks have tried other glutamate salts in low-salt soups. They proved less palatable than the monosodium form.

  353671415

• 5. The Right Dose

  ›

  Glutamate is not only a factory product. Tomatoes and cheese contain glutamic acid in this same form naturally, and so do stews and meat soups. In those foods, glutamate intensifies the umami flavor, and added MSG does the same job. It balances, blends and rounds the perception of other tastes.

  Amount matters a great deal. The best concentration varies by food. In clear soup, the pleasure score falls quickly once more than one gram of MSG per 100 mL is added.

  Cooks rarely use MSG alone. The ribonucleotide additives disodium inosinate, labeled E631, and disodium guanylate, labeled E627, seem to work synergistically with it. Ordinary salt is usually part of the mix as well.

  One blend carries the name super salt. It combines 9 parts salt with one part MSG and 0.1 parts disodium ribonucleotides. The ribonucleotides are themselves a mixture of disodium inosinate and disodium guanylate.

  How much of any of this the body can handle became a question for scientists.

  71415812

• 6. Putting Symptoms on Trial

  ›

  The idea that MSG causes discomfort has a name: Chinese restaurant syndrome. A 1995 report by the Federation of American Societies for Experimental Biology, prepared for the United States Food and Drug Administration, examined the claim. It concluded that MSG is safe when eaten at customary levels.

  The report did note one wrinkle. A subgroup of otherwise-healthy people developed an MSG symptom complex after 3 g of MSG taken without food. But the symptom reports were anecdotal, so MSG as the cause was not established.

  Good experiments must be designed carefully. They need a blinded, placebo-controlled design, and the MSG must be given in capsules because glutamates have such a unique aftertaste.

  In a 1993 study, 71 fasting participants received 5 g of MSG and then a standard breakfast. There was a single reaction. It came after the placebo, in a person who identified as MSG-sensitive.

  A study in 2000 recruited 130 subjects who reported sensitivity. They faced multiple challenges, and those showing at least two symptoms continued. Only two of the 130 responded to all four challenges. With prevalence that low, the researchers concluded the response was not reproducible.

  Other questions followed the same pattern. Studies of MSG and obesity have given mixed results, and the evidence does not support a causal link with asthma.

  2021223217

• 7. Doses and the Body

  ›

  Food Standards Australia New Zealand weighed in with its own technical report. It found no convincing evidence that MSG is a significant factor in severe illness or death. Symptoms resembling the syndrome may appear in small numbers of people given large doses without food. Those effects are neither persistent nor serious, and eating food alongside the MSG likely softens them.

  The report cited data from the United Kingdom showing an average intake of 590 mg a day. Extreme users, at the 97.5th percentile, consumed 2,330 mg. In a highly seasoned restaurant meal, intake of 5,000 mg or more may be possible.

  When a very large bolus above 5 g is swallowed, plasma glutamate rises significantly. It typically returns to normal within two hours. Foods that supply metabolizable carbohydrates blunt the peak at doses up to 150 mg per kilogram of body weight.

  Humans can metabolize relatively large quantities of glutamate, which the gut produces naturally during protein hydrolysis. Dietary MSG does not raise glutamate in the brain or affect brain function.

  The median lethal dose is between 15 and 18 g per kilogram of body weight in rats and mice. That is five times the figure for table salt, which is 3 g per kilogram in rats.

  One caveat remains from 1987 and 1995 expert reviews. A small number of unstable asthmatics may respond to doses of 1.5 to 2.5 g taken without food.

  2918193123

• 8. Labels and Names

  ›

  The United States Food and Drug Administration has given MSG its generally recognized as safe designation. Labeling rules are subtler than that status suggests. Since 1998, MSG cannot be folded into the phrase spices and flavorings.

  Glutamic acid and its salts also hide in other ingredients, including hydrolyzed vegetable protein, autolyzed yeast, hydrolyzed yeast, yeast extract, soy extracts and protein isolate. These must be specifically labeled. Yet the food industry uses the term natural flavors for glutamic acid, which lacks only the sodium ion. The FDA does not require disclosure of the components or amounts of natural flavors.

  In Australia and New Zealand, Standard 1.2.4 of the Food Standards Code requires MSG to be declared on packaged foods. The label gives the additive class name, such as flavour enhancer, followed by either MSG or the number 621.

  The European Union treats MSG as a food additive permitted in certain foods, within quantitative limits. It carries the E number E621 and the HS code 2922.42.

  On shelves, MSG travels under many names, including sodium glutamate and Sodium 2-aminopentanedioate. Trade names include Accent, made by B&G Foods of Parsippany, New Jersey, and Sazón, distributed by Goya Foods of Jersey City. Tasting Powder and Ve-Tsin, from Tien Chu Ve-Tsin, are others. Aji-No-Moto, from Ajinomoto, is made across 26 countries from a head office in Japan.

  In Pakistan, one of those names became the target of a ban.

  In January 2018, the Punjab Food Authority banned Aji-No-Moto, commonly called Chinese salt, from food products in Pakistan's Punjab Province. The product contains MSG.

  A wider prohibition followed. The Supreme Court issued an order on the 10th of February 2018, and the ban on importing and manufacturing MSG was enforced on the 28th of February 2018.

  The reversal came in 2024, when the federal government lifted the ban. It acted after objections from Japan and a review of the scientific evidence by an expert committee.

  The committee drew experts from several institutions, including the Pakistan Council of Scientific and Industrial Research, the National Agricultural Research Centre and the Pakistan Standards and Quality Control Authority. Its confirmation that MSG is a safe food additive ended the ban.

  4546474811