A meeting of great minds
As part of the European Sensory Network (ESN)'s 2007 seminar, held at the Ipanema Park Hotel in Porto, Portugal, several leading experts in the study of the fifth taste gathered to take part in an Umami Symposium, attended by an audience of nearly 60 scientists specializing in the study of flavour and science. Receptive to umami
Dr. Lucy Donaldson, Lecturer in Physiology at the University of Bristol, UK, kicked off the seminar by discussing the perception and modulation of the umami taste in humans. She began by pointing out that while there are a number of taste receptors on the tongue that are thought to be sensitive to umami, most notably those called mGluR4 and T1R1 and T1R3, which ones are most important and how they relate to each other is still a matter for further research. It is known, however, that umami can be perceived at both the front and rear of the tongue, with the latter being more sensitive to the taste among those who are not used to looking out for it. Umami and mood
Dr. Donaldson presented research that examined how a person's mood affects the perception of basic tastes, including umami. When depressed, the levels of the substances serotonin and noradrenaline in the human body increase, and this study examined the sensitivity to various tastes as the levels of these substances were varied. This showed that while the threshold (concentration required for a taste to be perceived) of sweet and bitter is modulated or varies according to levels of serotonin, the same does not hold true for salty, sour and umami. One area where umami is decidedly different from all other basic tastes, however, is the way in which anxiety affects the threshold. As Dr. Donalson explained, "if we plot the general anxiety levels against the umami threshold, what we find is that there is an inverse relationship ... it's the opposite of the other tastes." In other words, the more anxious someone is, the more readily they are able to taste umami. The enhancing effects of umami
Following on from the perception of taste, the event went on to examine the ways in which umami can enhance the enjoyment of food. Dr. Nina Barylko Pikielna of the Faculty of Human Nutrition and Consumer Science at Warsaw University of Life Science, who previously reported her work on umami at the Future of Food Engineering conference held in Warsaw in 2006, began her presentation by pointing out that many studies on the flavour-enhancing effects of umami focus on the extent to which the palatability of foods overall is increased by adding umami. Her research, meanwhile, carried out in conjunction with Eliza Kostyra, aimed to go one step further by examining the changes in perception of various flavour attributes due to the addition of umami in the form of monosodium glutamate and a mixture of inosinate and guanylate. Bringing out the best of foods
The study found that the greatest changes in flavour profile of the foods tested (chicken broth, vegetable soup, mushroom soup and green pea soup) occurred when only relatively small concentrations of umami substances were added. More interestingly, by breaking down the subject's reaction to the flavour into different components, it was discovered that perception of positive attributes such as 'bouillon-like', 'salty' and 'body' on the whole increased with added umami, while that of negative attributes such as 'burnt', 'bitter/pungent' or 'sharp' in fact fell. While Dr. Barylko Pikielna pointed out that further research was required in the area, her studies thus far had shed new light on how umami serves to enhance the taste of food. Stimulating appetites
One area where the enhancement of food through addition of umami is particularly important is in the diet of elderly people, who can be less likely to find food palatable, therefore losing their appetite, which has a knock-on effect on nutrition and well being. The next speaker, Natasja Essed, a PhD student at the Division of Human Nutrition, Wageningen University, the Netherlands, had conducted research into this topic by exploring whether a diet enhanced with umami could affect the energy levels and weight of Dutch institutionalized elderly people. The study did not discern any effect from adding umami, in the form of monosodium glutamate, to various foods consumed by elderly people over the four weeks it was carried out, although other studies have shown that older people do have a preference for higher flavour concentrations and adding substances such as monosodium glutamate that contain the umami taste can enhance palatability. Ms. Essed suggested that the result could be due to the fact that there is a good deal of sensory diversity among the elderly population, and a more individual approach may be necessary. The effect of naturally occurring, free glutamate present in foods should also be examined. A truly worldwide taste
This free glutamate in foods was examined in more detail by the final speaker, Dr. Miro Smriga of the European Committee for Umami. He pointed out that the natural occurrence of glutamate in certain foods has been exploited as a flavour enhancer for centuries, with one of the earliest instances being fermented fish sauces made by the Romans, and that most cultures today use free glutamate and other amino acids to improve the sensory quality of food. Thus, many of the most popular ingredients and seasonings around the world, including stock cubes, Worcestershire sauce, tomato sauce, Parmesan cheese and soy sauce are rich in natural glutamate and, therefore, umami. Dr. Smriga also pointed out that glutamate can be used as a healthier alternative to salt, as it enhances the savoury flavour of a dish in a similar way to salt, but without the attendant health risks and mentioned the emerging science of gastrointestinal taste receptors, which may contribute to the appropriate post-ingestional processing of foods.
[Audience Voice] European Sensory Network homepage: www.esn-network.com |
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