The Umami Story Hasn't Finished...

Prof. Tim Jacob

Interview with Tim Jacob, Professor, School of Biosciences, University of Cardiff

The word 'umami' is now widely recognized and used amongst chefs, food writers and food fans around the world, but not so long ago it was known only in Japan, or among scientists, and even then viewed with considerable skepticism. One man who has been aware of umami longer and understands it better than most is Tim Jacob, a professor who specializes in the relationship between smell and taste. We visited him in his laboratory at Cardiff University, UK, and asked him why, in his words, umami has had a "huge impact" on how we perceive taste and flavour.

A seasoned studier of taste

Cardiff University

Since completing his PhD in Biophysics at the University of East Anglia, professor Jacob has held a number of positions in institutions around the UK, and is currently a Professor in the school of Biosciences at Cardiff University, a post he has held since 1995. As a leading authority on issues concerning smell, he is particularly interested in the way in which our senses of taste and smell combine to allow us to experience the flavour of food and drink, and for almost twenty years, umami has been an important part of his research.

As Jacob recalls, "when I first started looking at taste in 1988, the textbooks had four tastes, and then I started reading research papers on a fifth, but it wasn't mentioned in the official textbooks." Even before scientists in the West began to seriously consider the possibility of there being a fifth taste, however, Jacob himself was sure that there was more to the four basic tastes theory than met the eye. "I always thought that taste was a complete fraud. How can sweet, salty, sour and bitter describe what we taste?"

The emergence of umami

Prof. Tim Jacob in his laboratory

The scientific consensus has certainly moved on a great deal in the intervening years, as Jacob explains, "umami has only been accepted in the west for the past 10 years or so, and the discovery of taste receptors for umami gave it credibility." The taste receptors he's talking about are the L-glutamate taste receptor, mGluR4, discovered in 1996 by Chaudhari et al. and two amino acid receptors, called T1R1 and T1R3, which were first reported in 2002 by Nelson et al. It was the discovery of these receptors on the tongue, which respond specifically to substances that contain the umami taste, that led to umami being taken seriously by scientists, chefs and those with an interest in food, and it being recognized as one of the basic tastes alongside sweet, salty, sour and bitter.

Jacob, however, gives a more fundamental explanation of the importance of umami as a taste, which touches on the basic role of taste in the way we eat. "The purpose of taste," he says, "is to drive appetite ... umami is the taste of proteins and amino acids, so it makes perfect sense that we have to have the umami taste."

The importance of taste

As Jacob explains on his website, we are naturally disposed to find appealing the taste of foods that are essential for our survival, and react adversely to the taste of foods that may do us harm. Thus, for example, we find sweet things pleasant because sweetness is the taste of sugars and carbohydrates that we require to function, in the same way as we crave the taste of salt, which is also essential to life. Bitterness and sourness, by contrast, are tastes that we find unpleasant on the whole, because most substances that are poisonous or harmful to human beings are bitter, and foods that go off generally turn sour or acidic.

With this in mind, argues Jacob, it stands to reason that we find the umami taste pleasant because it is contained in amino acids, which are the building blocks of protein, which in turn is another substance essential to life. The acceptance of umami as a basic taste has therefore been essential to gaining a fuller understanding of why we find certain foods delicious, but while this is undoubtedly of interest to scientists, what impact does it have for chefs and everyday cooks?

Umami and health

One factor is that simply by being aware of the existence of the fifth taste, chefs can exploit that knowledge to make their cooking more appealing. "It's like an artist having another colour to paint with," suggests Jacob. "If you don't recognize its existence, you don't know it's there." One problem that may impede people's acceptance of umami is that they have trouble experiencing and identifying it for themselves. So what is the best way to allow people to do this? "The best way to describe umami is to mention something like parmesan cheese, which has a very distinctive taste, or in Britain, it would be things like Marmite and Bovril, because you know that one way or another most people have experienced it."

Jacob believes that not only can umami be used to make food tastier, but at the same time allow us to eat more healthily. He compares the cuisine of Japan, where umami has been understood and exploited for much longer, with that of his native country and environs. "When you think about the UK and Northern Europe, the diet is weighted towards carbohydrates and sweet things ... umami is satisfying, but it doesn't come from carbohydrates, and it's not linked to obesity." The point being that uniquely among the basic tastes that we find pleasant, foods associated with umami, that is to say those containing amino acids and protein, are on the whole free from detrimental effects on health.

When health and umami are discussed, however, it is difficult to avoid the topic of monosodium glutamate, or MSG, which is one of the main sources of the umami taste in processed foods, and is often accused of being detrimental to health. On this topic, Jacob says, "if there is a magic ingredient that enhances flavour, then people will use it, and large doses will cause problems for some people. With all the research that's been done, including the government-sponsored research, there have been no problems when consuming MSG, within normal limits, which are 0.5-1.5g per day on average."

Just the beginning...

One point that Jacob is keen to stress is that now umami has been recognized and accepted, and the umami specific taste receptors identified, it doesn't mean that there is no more left to discover about the fifth taste. On the contrary, he says that, "the umami story hasn't finished yet. If people don't believe in it, they're not going to research it, but when they do, they'll do research, and it throws up interesting stuff ... the umami taste is more complex than people give it credit for."

Umami and synergism

One area where this is the case is in relation to the three taste receptors mentioned earlier, their location and their role in bringing about the synergistic effect of umami. This, as regular readers will be aware, is the phenomenon where if two or more of the substances that cause the umami taste, namely glutamate, guanylate or inosinate, are combined in food the intensity of the umami taste increases by up to 900%. Asking the Professor why this occurs, he explained that, although not yet confirmed for certain, it is theorized that each of the receptors, mGlu4 and T1R1 & T1R3, are sensitive to separate umami substances, so that when these are combined in food, they stimulate more than one taste receptor, thereby enhancing the taste sensation.

A true taste bud tantalizer

A diagram of the human tongue

Another area for further study that relates to this is the position of taste buds and receptors in the mouth. Many people may be familiar with diagrams of the human tongue, neatly divided into areas that respond to different basic tastes, such as the sweet area, and the bitter area. Although it was thought for many years that this was how the taste buds worked, this theory was subsequently disproved, partly due to the emergence of umami, and scientists began to agree that all tastes could be experienced all over the tongue. But again, Jacob suggests that this is not the whole story either. In fact, "certain regions are more sensitive to one or two tastes [so] it's a case of throwing the baby out with the bathwater, to throw out the idea that there are sensors [for certain tastes] in certain areas."

In fact, taste buds are not simply located on the tongue, but also on the palate, esophagus and throughout the oral cavity. Jacob is particularly keen to point out that there is a high density of umami taste buds on the palate in addition to those on the tongue, and what is more, these are connected to the brain by the facial nerve, which is separate to the nerves serving the tongue. Thus, he says, "umami has its own direct link to the brain."

Scientific study into the workings of umami in particular and taste in general continues apace, but in the meantime, all of us can of course enjoy the taste of umami for ourselves, and the Professor is no exception. He is particularly fond of the way umami is harnessed in Japanese cuisine, in everything from sashimi dipping sauce to dashi, and he and his wife are regular patrons of Cardiff's three Japanese restaurants. With this finely developed appreciation of the fifth taste, who better to further the scientific study of umami?