Today's Food 101 column about taste from the Post:
Umami Dearest
Wednesday, September 4, 2002; Page F01
Some four thousand years ago, Chinese philosophers speculated that the world was made of five elemental substances: metal, wood, earth, fire and water. Two thousand years later, the Greek philosophers pared down the list to four: air, earth, fire and water.
A similar state of affairs has prevailed in the philosophy of taste. The Chinese believed in five fundamental tastes corresponding to their five elements: sweet, salty, bitter, sour and pungent. Perhaps as a legacy of our forebears, we in the West have limited our list to four: sweet, salty, bitter and sour. But are there more?
Four years ago I wrote in this space about umami (oo-MAH-mee, or if you prefer, Ooh! Mommy!), which, I cautiously stated "may actually represent a separate family of savory tastes . . . similar to the family of sweet tastes that are stimulated by sugar [and artificial sweeteners]." My caution was prompted by the fact that many scientists at the time were reluctant to increase their four basic tastes to five until some smoking-gun evidence came along. Philosophical speculation is one thing, but science requires verifiable fact.
Today, there is enough evidence to settle umami comfortably into place as a legitimate fifth taste. As a result, the popular food media are awash in a veritable tsunami of umami stories. Maybe it's time for a summary of what we know about it.
In 1907, chemistry professor Kikunae Ikeda of Tokyo Imperial University wrote, "There is a taste which is common to asparagus, tomatoes, cheese and meat but which is not one of the four well-known tastes of sweet, sour, bitter and salty." He named it umami, from the Japanese word umai, for "tasty." It has since been characterized as everything from meaty to savory and even chicken-brothy. Undoubtedly, some of the early opposition to accepting umami as a legitimate taste stemmed from our inability to describe it in words, which gave it a somewhat mysterious aura. But just try to describe what salt tastes like without using the word salty.
Ikeda was able to extract the essence of umami from the seaweed kombu; it turned out to be a family of chemicals called glutamates (glu-TAM-ates), which are salts of glutamic acid, one of the amino acids that are the building blocks of proteins (see box below). No less a slouch at business than at chemistry, Ikeda sold his formula for making monosodium glutamate (MSG) in 1917 to the Ajinomoto Co., which still supplies about one-third of the world's 200,000 tons of MSG per year. You can find it labeled Ac'cent in your supermarket.
Because of high glutamate content, such foods as mushrooms, tomatoes, fermented soy sauce (not all soy sauce is fermented) and Parmesan cheese, especially Parmigiano-Reggiano, deliver whopping umami kicks to our cooking.
Glutamic acid is the most common among the 20 or so amino acids that make up all animal and vegetable proteins. Wheat protein, for example, contains more than 30 percent glutamic acid (named after wheat's gluten), while the proteins in milk and meat contain about 20 percent and 15 percent glutamic acid, respectively. But proteins are generally huge molecules, and we can taste only molecules that are small enough to "latch onto" the taste-receptor molecules in our taste buds. So proteins become tasty only after they are broken down into their component, small-molecule amino acids. This happens, for example, during cooking meat or fish, fermenting soybeans, maturing fruits and ripening cheese.
Unknowingly, the virtues of umami have been exploited by humans for thousands of years. The Greeks and Romans made a sauce called garum, or liquamen, by salting and aging a mess of fish and fish guts. The salt draws out liquids, the liquids ferment and the proteins break down both physically and chemically into their flavorful amino acids, mostly glutamic acid. Similar fish sauces -- among them the pissalat of Provence, nuoc-mam of Vietnam, nam pla of Thailand and nuc nam of China -- are still used as flavor boosters. They're all absolutely loaded with umami.
The Latest Word
Umami got a big boost in the Western world early in 2000, when scientists at the University of Miami discovered a specific taste receptor for glutamates on the human tongue. That made believers out of a lot of skeptics. And just this year, in the March issue of the research journal Nature, scientists at the Howard Hughes Medical Institute, University of California at San Diego and the National Institutes of Health reported their discovery of a taste receptor that is sensitive to several of the amino acids found in proteins, not just glutamic acid.
So East may be East and West may be West, but Rudyard Kipling to the contrary notwithstanding, the twain finally appear to have met.
Among other things, what's exciting about the recent scientific findings is their evolutionary implications. Humans and other mammals have developed taste receptors for saltiness, with which to seek out essential sodium; we have developed taste receptors for bitterness, with which we could avoid plants containing bitter, toxic alkaloids; we have taste receptors for sweetness as a means of identifying carbohydrates, which are essential for energy. (Although most carbohydrate molecules are too big to interact with our taste receptor molecules, they are easily broken down into small, tasty molecules of sugars.) But until now, we haven't known of any receptors that might have helped us to seek out vital proteins by tasting and enjoying their breakdown products, the amino acids. That, it seems, is just what our umami receptors have been doing all along. |
