Fat lot of good: Scientists find a ‘sixth basic taste’

Some 20 years ago, umami was recognised universally as the fifth taste — described variously as ‘meaty’ or ‘savoury’, found typically in meat and seafood.

Published:July 29, 2015 3:55 am

For centuries, human cultures have recognised four basic tastes: sweet, sour, salty and bitter. In 1908, Japanese chemist Kikunae Ikeda identified a fifth basic taste — umami — imparted by the chemical monosodium glutamate, or MSG. Some 20 years ago, umami was recognised universally as the fifth taste — described variously as ‘meaty’ or ‘savoury’, found typically in meat and seafood; mushrooms, especially truffles; anchovies; and cheeses, particularly parmesan.

Research has now produced considerable mechanistic data to indicate there may be a sixth basic taste: fat. The researchers have proposed the name “oleogustus” to refer to the sensation. “Oleo” is the Latin root word for oily or fatty, and “gustus” refers to taste.

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“Most of the fat we eat is in the form of triglycerides, which are molecules comprised of three fatty acids,” Richard D Mattes, distinguished professor of nutrition science at Purdue University and a study author, said. “Triglycerides often impart appealing textures to foods like creaminess. However, triglycerides are not a taste stimulus. Fatty acids that are cleaved off the triglyceride in the food or during chewing in the mouth stimulate the sensation of fat.
“The taste component of fat is often described as bitter or sour because it is unpleasant, but new evidence reveals fatty acids evoke a unique sensation satisfying another element of the criteria for what constitutes a basic taste, just like sweet, sour, salty, bitter and umami.

“By building a lexicon around fat and understanding its identity as a taste, it could help the food industry develop better tasting products and with more research help clinicians and public health educators better understand the health implications of oral fat exposure,” he said.

The researchers used perceptual mapping to demonstrate that medium- and long-chain nonesterified fatty acids, or NEFA, have a taste sensation that is distinct from sweet, sour, salty, and bitter.

Although some overlap was observed between the NEFA and umami tastes, the overlap was likely due to unfamiliarity with umami sensations rather than true similarity, the researchers said. The shorter- chain NEFA stimulate a sensation similar to sour, but as chain length increases, this sensation changes, results of the research showed.

The basic ‘fat’ taste isn’t appealing by itself, the researchers said. What it could do to flavours though, was, they said. Mattes explained this was similar to the effect that bitter or MSG tastes, which are not pleasant on their own, had on the flavour of beer, chocolate, and a range of other foods. “Many things that are unpleasant in isolation, in fact contribute greatly to the appeal of foods,” Mattes was quoted as saying.

Earlier in February this year, Australian scientists from Deakin University in Melbourne reported similar results in the Flavour journal. “The evidence now is comprehensive and overwhelming enough to call fat a taste,” lead author Russell Keast told the Australian Associated Press.

(ADAPTED FROM STUDY EXTRACT & PURDUE UNIVERSITY RELEASE)

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