Umami - How I love Ya

Can there be anything like the mouth watering taste of new season's asparagus in spring or ripe tomatoes in the height summer? Is there a mouth fill quite as distinctive as nori or dried wakame on your sushi rice? Ever wondered why? It's umami.

It was traditionally understood that our tongues could discern only four tastes - sweet and sour and bitter and salty. These were known as "primary" tastes, which, like primary colours, could not be replicated by mixing together any of the other primary tastes. But in 1908 a Japanese researcher, Kikunae Ikeda, working on isolating the flavor in seaweed broth, discovered a fifth primary taste.

This new taste was dubbed umami, from the Japanese word for "tasty" or "brothy" or perhaps "delicious" or "yummy".

But what was it ? In the laboratory of the Tokyo Imperial University the ingredient causing the taste was identified as an amino acid known as glutamic acid.

In 1913 another Japanese scientist discovered that a further substance was responsible for the yumminess of bonito flakes and in 1960 yet another substance was isolated in dried mushrooms. These latter two ingredients were, respectively, nucleotides known as inosinate and guanylate. The three chemicals are collectively known as umami.

Umami coats the tongue and is detected by particular taste receptors which in turn gives rise to secretion of neurotransmitters which convey taste signals to the brain.

It is thought that umami flavour is most potent when accompanied by aroma and the appearance of food. This fits with early research in the USA which found that umami compounds when tasted alone were unpalatable yet when added to food improved its taste.

So is it any wonder that we drool over ripe red fragrant tomatoes or beautiful green asparagus or pick up on the yumminess of aroma rich seaweed or bonito stock, truffles or mushrooms?

Umami taste is present in seafood, meat, vegetables and other foods such as parmesan cheese and green tea. Brillat Savarin was pretty close when he characterised osmazome - the yumminess in veal stock typifies the flavour common to savoury substances such as meat, cheese and mushrooms.

There are high quantities of umami elements in seafood such as sea weed, bonito, mackerel, tuna, prawns, squid , oysters and shellfish and in vegetables such as potatoes and carrots and soy beans.

Heston Blumenthal carried out some experiments and in conjunction with scientists at the faculty of Reading University in the UK wrote an academic paper on umami in tomatoes. The result of the research showed that the umami substance in tomatoes is clearly more abundant in the inner part so that it s important to include the pulp and seeds in soups and sauces.

The most recent paper I could find on umami was published on July 1 this year in the American Journal of Clinical Nutrition.

It is clear from this study that many questions remain unanswered, chief amongst them being the reason for the unpalatability of pure umami. While several specific receptors that mediate umami taste have been recently identified research on the subject is expected to continue into the next century.

In the meantime enjoy your seaweed safe in the knowledge that all you are doing is exciting sensory fibres that convey taste signals to neurons in the orbitofrontal cortex of the brain.

God, don't let them start on sex!