05 May 11 Is umami really a fifth taste?
Taste, a sense often neatly organised into four categories –– sweet, sour, bitter and salty, and more latterly five with umami –– may, in fact, be significantly more complicated.
According to Bruce Halpern, professor of psychology, neurobiology and behaviour at Cornell University, New York, mammalian sensory systems are complex, and he gives the following analogy. “We only have four photoreceptors, so people might conclude that we can only see four colours, but we know from seeing wide spectrums of colour, that this is not true.”
Just as colour cannot be described in four colours, taste cannot be neatly organised into four or five categories. “We really don’t know how we fully taste,” he notes.
According to Halpern, some scientists believe four or five tastes exist, while others are convinced these recognised tastes are high points or patterns in a broad spectrum of perceptions of taste. There is evidence to support both sides.
Researchers are constantly disproving theories once thought to be true. For example, one study in Germany was mistranslated and thought to suggest that different regions of the tongue picked up on different tastes. Halpern explains that the interpretation of the study was “completely untrue,” and disproved over 20 years ago, yet is still included in some secondary school and even university textbooks.
Halpern believes one explanation for the little knowledge we have about how humans perceive and process taste is because the majority of molecular data comes from studies performed on non-human species.
“When you try to study the physiology of taste and your data is largely from one species, associating it with the psychophysical or behavioral or pleasantness judgments of something from another species is very difficult,” Halpern says.
In 1908, Japanese chemist Kikunae Ikeda, a professor of the Tokyo Imperial University, extracted a single salt of glutamic acid, commonly known as monosodium glutamate, or MSG, from seaweed. When Ikeda published his findings, he equated this flavorful compound with the term “umami.”
Some scientists today consider umami the fifth taste.
Halpern believes that umami isn’t a taste, but a concept. In Japanese, umami is used sparingly to describe something exceptional; for example, the best french fries you’ve ever tasted.
Prof Harry Lawless, food science at Cornell, explains that umami is modified in its definition in western cultures and has been translated as delicious, savoury, meaty and brothy. According to Lawless, umami is detectable in any water solution of monosodium glutamate. Glutamic acid is not an unusual or artificial ingredient and is naturally occurring in foods such as tomatoes, provolone cheese, and mushrooms in low concentrations.
Though scientific research supports the human perception of umami, some are hesitant to label it a ‘fifth taste,’ included with bitter, salty, sweet and sour. “Umami is kinda BS –– there are only four tastes. I’ve never tasted anything ‘umami’ before,” says Thomas Moore ’14.
Our brains respond to [umami]. We just hadn’t identified it until relatively recently. It is hard for people to change … this ‘umami denial’ may be an anti-science reaction,” says Prof Kathy Arnink, food science at Cornell.
New theories emerge, old theories are disproved. Opinions change as the science of sensory and taste perception evolves. The way Halpern sees it, “we learn more all the time, but there is still an awful lot more to be learned.”
“I have observed a tendency for some people to disbelieve all new scientific findings. There seems to be a misunderstanding about the scientific method among part of the non-scientific population,” says Arnink.
“Science is all about changing and improving our knowledge. Of course we will sometimes refute earlier ideas, or, as in this case, add to them. That is not a failure of science. That is a goal of science- improving our ideas and knowledge.”
Source: The Cornell Daily Sun
For a long time, scientists debated whether umami was indeed a basic taste; but in 1985 at the first Umami International Symposium in Hawaii, the term Umami was officially recognised as the scientific term to describe the taste of glutamates and nucleotides. Now it is widely accepted as the fifth basic taste.
Umami represents the taste of the amino acid L-glutamate and 5’-ribonucleotides such as guanosine monophosphate (GMP) and inosine monophosphate (IMP).
It is described as a pleasant “brothy” or “meaty” taste with a long lasting, mouthwatering and coating sensation over the tongue. This is due to the detection of the carboxylate anion of glutamate in specialised receptor cells present on the human and animal tongue.
Its fundamental effect is the ability to balance taste and round the total flavour of a dish. Umami clearly enhances the palatability of a wide variety of foods. Glutamate in acid form (glutamic acid) imparts little umami taste; whereas the salts of glutamic acid, known as glutamates, can easily ionise and give the characteristic umami taste. GMP and IMP amplify the taste intensity of glutamate.