What Is Umami? The Fifth Taste and the Chemistry of Savouriness
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A Japanese chemist tasting his wife's soup in 1908 decided that the savoury quality of the seaweed broth was not sweet, sour, salty or bitter but something else, boiled down thirty-eight kilograms of kelp to find out what, and extracted crystals of glutamic acid. Kikunae Ikeda named the taste umami, deliciousness, patented a way of making the seasoning, and was politely ignored outside Japan for ninety years, until the receptors on the human tongue that respond to it were identified and the fifth basic taste became official. It is the taste of parmesan, anchovies, ripe tomatoes, soy sauce, mushrooms, cured ham and human milk.
What the tongue detects
Taste, as distinct from flavour, is the small set of qualities detected by receptors on the tongue, and each one exists because it reports something worth knowing about food: sweet means energy, salt means minerals, sour means acid and possible spoilage, bitter means possible poison. Umami reports protein. The molecule that triggers it is glutamate, an amino acid that is a building block of every protein, and the tongue detects it in its free form, unattached to a protein chain, which is what happens when protein is broken down by ripening, curing, fermenting, ageing or cooking. A food rich in free glutamate is a food in which protein has already been partly digested, which is a signal of a nutritious and easily used meal, and the receptor that detects it, a modified form of a glutamate receptor found in the brain, was identified in 2000 and 2002, which is when the argument about whether umami was a real taste ended.
The synergy
Umami has a feature no other taste has, which is that two classes of compound multiply each other. Glutamate on its own gives a moderate savoury effect; add a small quantity of a nucleotide, inosinate from meat and fish or guanylate from mushrooms, and the perceived intensity rises by up to eight times, because the nucleotide binds to the receptor in a way that makes it hold glutamate more tightly. Cooks discovered this long before chemists explained it, which is why the classic stocks of the world pair the two without knowing:
- •Japanese dashi: kombu seaweed, which is glutamate, with dried bonito flakes, which are inosinate
- •Italian ragu: tomatoes and parmesan, glutamate, with meat, inosinate
- •Chinese stock: dried shiitake, guanylate, with pork or chicken bones
- •French stock: veal bones and a mirepoix of vegetables, simmered until both are extracted
- •The British store cupboard: Worcestershire sauce, anchovy paste and yeast extract, all concentrated glutamate
Where it comes from in food
Anything that ages, ferments, dries or cures gains umami, because time and enzymes break proteins into free amino acids. Parmesan aged three years has one of the highest glutamate contents of any food, and the white crystals in it are partly the amino acid itself; soy sauce, fish sauce, miso, anchovies, cured ham, ripe tomatoes, dried mushrooms, seaweed, marmite and stock are the standard sources, and slow cooking, browning and drying all increase what is there. Breast milk contains free glutamate at about ten times the level in cow's milk, which is thought to be why the taste is accepted from birth when bitter and sour are rejected. The reason a tomato tastes better ripe, a steak better aged and a cheese better old is in every case the same molecule accumulating.
The seasoning and the scare
Ikeda's patent produced monosodium glutamate, the sodium salt of the amino acid, manufactured now by fermenting sugar with bacteria in the way that yoghurt and vinegar are made, and it is chemically identical to the glutamate in a tomato. Its reputation in the West was destroyed by a letter to a medical journal in 1968 describing numbness and palpitations after Chinese meals, which produced decades of headlines, a name that has since been dropped as racist, and a body of research that has consistently failed to find an effect: double-blind trials, including those on people who report being sensitive, do not distinguish it from placebo at ordinary doses, and the regulators of the United States, Europe and the United Nations classify it as safe. The practical case for it is that it delivers savouriness with about a third of the sodium of salt, which is why health authorities have begun to look at it as a way of cutting salt rather than as a hazard.
The sixth and the rest
Umami's acceptance opened the question of how many tastes there are, and the candidates now under investigation include fat, for which receptors have been found, calcium, starch and the metallic and the sensation of water; the ones that will be accepted are those with a dedicated receptor, a distinct quality and a reason to exist. Meanwhile the taste that took ninety years to be believed has become a standard tool: chefs speak of layering it, food manufacturers add it under a dozen names, and the seaweed broth that Ikeda's wife made in 1908 turns out to have been a demonstration of the chemistry of every good stock in the world.
The takeaway
Umami is the savoury taste of free glutamate, an amino acid released when protein is broken down by ageing, curing, fermenting or cooking, identified by Kikunae Ikeda in 1908 and confirmed as a fifth basic taste when its receptor was found in 2000. Its intensity multiplies up to eightfold when glutamate meets the nucleotides in meat, fish or mushrooms, which is why dashi, ragu and every classic stock pair the two, and monosodium glutamate is the same molecule, cleared by every safety review since the scare of 1968.