Umami - the fifth taste

Food and science sit uncomfortably together in the minds of most consumers, but when it comes to large-scale food production, their overlap is often unavoidable. To try and bridge this void, the organisers of this year's Cheltenham Festival of Science invited the public along to hear how science is unravelling the mysteries of taste. In particular, they focused on why the Japanese believe that beyond the four tastes of sweet, sour, salty and bitter, there is a fifth called umami -- a savoury taste so appealing that it promotes a feeling of well-being.

Whether food scientist or foodie, the event revealed some interesting research results that could lead to new appetite-controlling food products in future.

For the past few decades, gastronomists around the world have debated why this so-called fifth taste, which has been part of Japanese cuisine for centuries, has eluded Western palates. It was Japanese scientist Dr Kikunae Ikeda, back in 1908, who first discovered that glutamic acid, an amino acid, was responsible for the umami taste. More recently, scientists have found that the natural compounds inosinate and guanylate also play a synergistic role in making foods that contain glutamate taste even better.

All of these compounds occur naturally in certain foods, such as meat, fish, vegetables, and dairy products -- even mother's milk. But it has proved surprisingly difficult to pin down exactly what the umami taste is, and the effect it has seems to go beyond simply taste to something more spiritual.

Taste receptors

Researchers have now identified the receptors on the tongue that respond to glutamate. And the more scientists explore the umami concept, the stranger it gets.

Speaking at the Festival, Edmund Rolls, a professor of experimental psychology at Oxford University, explained how brain scans are being used to show what happens in our brain as we eat different foods. It appears that eating glutamate activates our taste centres in a way that no other substance does. "Whereas most foods activate a part of the brain called the secondary cortex, glutamate also activates another part of the brain, the left lateral orbifrontal cortex," he says. Could this be why it seems to act on a second level, giving people an emotional feeling of well-being?

The Japanese may not know how it works but they are experts in producing food rich in umami. For example, the Japanese stock called dashi -- the base for many Japanese dishes -- is rich in umami or glutamate.

Guest speaker Ichiro Kubota, executive chef at the London restaurant Umu, explained to the festival audience how dashi can be prepared using umami-rich ingredients, such as kombu (the seaweed kelp), shitake (mushrooms) and bonito (dried fish flakes). His experience of umami is "the indescribable but comforting taste of mum's home cooking."

Enhanced flavour

Even the Japanese rice wine saki is high in glutamate and is said to enhance the experience of eating food -- a concept that Kumiko Ohta, Xavier Chapelou and Jean-Louis Naveilhan, founders of saki import business Isake, are keen to impart to the western market. Whether eating Japanese or western food, they say the saki combines with the glutamate in food to produce a synergistic umami affect that our tongues and brains find very appetising.

But you don't have to be Japanese or eat Japanese food to appreciate umami. It is present in western diets too in the form of parmesan cheese and sun-dried tomato, mushrooms and tuna, to name but a few. It is also present in the synthesised form of monosodium glutamate (MSG).

This compound was first introduced to UK consumers in Chinese food but is now used in many other savoury products. However, in recent times consumers have complained of 'Chinese restaurant syndrome' and believe that MSG is responsible for feelings of nausea and headache experienced after eating Chinese meals.

This has resulted in some producers avoiding its use in products. However, manufacturers of MSG have conducted many studies and say they can find no such effect.

Professor Rolls believes such symptoms may be explained by excessive dosage of MSG by some Chinese restaurants -- after all, if salt were added in excessive amounts that too would make us feel ill.

It is an issue that gastronome and restaurateur Heston Blumenthal has delved into. He questioned whether MSG could really be the culprit consumers perceive it to be, as glutamate is present in many other foods, including ripe tomatoes and cheese. He said that subconsciously western consumers had been choosing the umami flavour when they ate cheese or sun-dried tomatoes -- the basis of many pizzas.

Food writer and presenter of the BBC's Full on Food show, Stefan Gates, speculated that such food intolerance was probably widely over reported by consumers: "In surveys, 20% of people claim to have a food allergy of some kind when, according to British Nutritional Foundation statistics, only 1.4% of them actually do."

When it comes to umami, he compared the Japanese liking of dashi to UK consumers' liking for Cheesy Wotsits. This popular savoury snack contains both cheese powder and MSG, so is high in glutamate. He even suggested Westerners would more readily accept the concept of umami if it had the more western name 'wotsit'.

Appetite Control

But umami could have wider implications for western consumers. Recent research outlined by Professor Rolls suggests that it could play a part in controlling appetite.

Rolls explained that while we find the umami taste pleasant when we are hungry, this diminishes as we become fuller, and when we are completely satiated we do not find umami nearly so appetising.

Amidst the current epidemic of obesity, such a discovery could help food producers develop products that not only give consumers a comforting feeling, but preventing them from over eating.FM