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Healing power of taste: Can an elusive flavour dimension help tempt hospital patients to eat?

Essential to Japanese cuisine, umami is the elusive flavour dimension that gives foods their moreishness. So can a collaboration of scientists and chefs harness its effects to help tempt hospital patients to eat?

I'm sitting in a darkened laboratory at the University of Reading, the fluorescent harshness of a computer screen cutting through the strangely seedy glow of the red lamps above. In my hand is a tiny medicinal brown glass bottle. I sniff its contents and, drawing in the cloying, custardy smell, try to decipher whether I detect a sour milk aroma, nuttiness, maltiness or vanilla. Reluctantly, I take a sip.

My neighbours – from whom I hear the occasional shuffle or click of glass on counter – are highly-trained taste panellists and the glass bottles contain sip-feeds, high-nutrient liquid meals that are heavily relied upon in hospitals.

I find the feeds pretty repugnant, but these experiments form vital early research into a quietly progressing project that aims to unlock the secrets of umami – the name for the fifth taste (the others being sweet, salty, bitter and sour). In a hushed room adjoining the lab, every inch of data gathered from every sip of every tiny bottle is being analysed whilst just along the Thames at Bray, chefs at one of the world's very best restaurants are cooking up their input, too – all with the hope that an oft-misunderstood taste will eventually make an altogether more satisfying eating experience for elderly patients.

What exactly is umami? At an Umami Symposium in central London earlier this year, at which exquisite Japanese was served (umami flavours are central to Japanese food), a host of top-notch chefs gathered to discuss the elusive flavour, including Kyle Connaughton, the head chef of the development kitchen at The Fat Duck. When asked to define umami, they glazed over with the look of men grappling to find the right words. To chef Kunio Tokuoka, it's "intrinsic to life, like breathing", whilst Ichiro Kubota of London's Umu restaurant said "it's the character of the ingredients". Yoshihiro Murata bowed out with "I don't know – pass" and Takashi Tamura concluded concluded that it is "the hidden thing that you can't explain".

The crepuscular exercise went far to explain why the taste – fundamental as it is to most of our diets – is relatively unknown. In the West, we tend to lump for "savouriness" as the best translation. And all over the world, for better or for worse, many associate umami with its chemical manifestation, monosodium glutamate (MSG).

Though unwittingly used to add depth of flavour to foods for thousands of years – from Roman fermented fish sauce (garum) to a "splish" of Lea & Perrins – umami was officially discovered by Dr Kikunae Ikeda of Tokyo Imperial University only 100 years ago. Like most Japanese, his diet was largely based around a stock-based broth, dashi, made by soaking kombu (kelp seaweed) in soft water. He found that the umami, literally translated as "deliciousness", in the stock – that he had attributed to his wife's cooking – came from the "meaty" taste of glutamate imparted by the kombu. Ikeda went on to invent MSG.

Essentially, umami is the taste of the amino acid glutamate and, it was later discovered, the nucleotides inosinate and guanylate. It was only as recently as 1996 that scientists finally isolated umami-sensitive receptor cells on the tongue, elevating umami beyond doubt to scientific fact.

Unlike bitterness and sourness, which often make us recoil (to avoid toxins and unripe or off foods), umami, like sweetness, is a pleasant sensation. It is thought that we are naturally predisposed to "liking" umami because of our need for protein and nucleic acid, which is crucial to our health. Indeed, breast milk is extremely high in glutamate, implying that it is something that the body requires from the very first moment in life.

So, when Dr Ikeda smacked his lips and declared "Umai!" after a spoonful of his wife's broth, he was not only registering a "delicious!" taste but providing his body with essential proteins, too. You're doing the same when you add ketchup to your chips, or fish sauce to your green curry.

And by combining glutamates with certain nucleotides (as happens when parmesan is added to Bolognese) the umami taste is heightened by up to eight times. What's more, by adding umami to dishes, we can cut the amount of salt and fat needed to make a delicious dish. Some of Japan's key cooking ingredients – soy sauce, dashi, miso, nori and shiitake mushroom – are the most umami-intense natural foods. It is perhaps no surprise that Japan has some of the lowest obesity rates and greatest life expectancy rates in the world (something that may change given their faddish discovery of wine, coffee, chips and pasta).

When Heston Blumenthal, co-author of Dashi And Umami, written in collaboration with Nobu Matsuhisa, announced at the Cheltenham Science Fair in June that he was working on developing hospital food with the University of Reading (who awarded him an honorary Doctor of Science degree in 2006), the sensational headlines were quick to follow. No, bacon ice-cream won't be served by the NHS, nor is research funded by the Government. In fact, sponsored by Research into Ageing, the research arm of Help the Aged, the project hopes to revolutionise hospital food for elderly people. As Blumenthal put it, the team is "try[ing] to excite older people with food again". And umami may be the answer.

Back in the Sensory Science Centre at Reading, Dr Lisa Methven, a world expert in food science, explains, "as people get older, their taste and odour thresholds increase, so they may need more flavour to taste sufficiently and enjoy food". Not only does umami "enhance flavours and increase taste" and lead to eating essential proteins and amino acids, it has also been proved to increase salivation and gut motility – both of which decline in old age.

So, why not take the lead of the food industry and add a few grams of MSG to hospital meals? It's a hugely contentious chemical and one that has been dogged with health questions since "Chinese restaurant syndrome" was coined in 1968 by Dr Ho Kwan Man Kwok. He claimed that MSG in Chinese food causes "numbness ... general weakness and palpitations". MSG was seen as the incriminating link. It's sanctioned by health authorities the world over and is chemically identical to naturally occurring glutamates, but no-one can agree whether MSG is physiologically harmful or not – and, either way, trial by media seems to have called a guilty verdict, at least for now.

As it's not acceptable to put MSG into food, "we're looking for natural foods to get an umami impact", explained Dr Methven. This stage of testing is a precursor to elderly volunteer tests and final patient testing phases, due next year. Samples are tasted in highly-controlled circumstances, minimising environmental and social impacts on taste judgements. Hence red lights and darkened booths. A hatch slides up and I am next presented with a tray of three mini Pyrex dishes of cooked mince. "We smell them first," directs Lisa Grandin, an umami supertaster and panellist on the project. Her umami receptors are particularly sensitive to the "lingering, meaty aftertaste" of umami, so much so that she is unable to eat certain MSG-laden foods, not because of a physiological reaction but because of the overwhelming taste that, through training at the Sensory Science Centre, she has become so aware of. "It's not a salty taste, you don't notice it straightaway, it's an aftertaste, it hits you later." We work our way through the three samples, sniffing and chewing then cleaning our palates with water and crackers between bites.

I rightly guess the MSG-laden sample – it's stronger tasting, more intense and meaty, even salty. But the shiitake mushroom sample is also just as tasty, with a slightly earthier flavour and a definite whiff of garlic. The control sample isn't bad – it's the standard NHS hospital recipe – but it lacks any moreish oomph.

The aim is to emulate MSG samples as closely as possible without the interference of other flavour compounds that can come through from added umami-rich foods. As Dr Methven explains, it's about balancing the combinations of flavours, glutamate and four different nucleotides "to get a big hit and rounded note and to make sure it doesn't smell of garlic."

Garlic? It's all down to flavour volatiles, I am told. Shiitake mushrooms have some of the same flavour compounds in them as garlic and onions, and so give off a garlicky flavour. "So we try to optimise the extraction conditions and look for other foods that are high in umami and then experiment using them together."

And this is where Blumenthal's expertise comes in. "Heston will say, 'Have you tried this? Have you tried that?' He gives ideas – 'Hold on a minute, we cook it like this, this is the way we think you could do it.' We compare it to the way hospitals do it, and bring in Heston's catering technology and ideas. For example, they have a lot of experience of working with seaweed." The book, Dashi and Umami, springs to mind.

Dr Methven's colleague, Dr Maria Dermiki, has visited The Fat Duck to watch how Blumenthal and Connaughton cook and develop food ideas and to see how far these can be recreated in hospital kitchens. "After starting from an academic point of view, we have this advice. They'll say, 'I use this, I don't know why it's good, but it is.' We then work out why it works. It's an ongoing process."

Eventually, they hope, appetising, umami-laden dishes will appear on hospital menus, encouraging elderly patients to eat and most of all, enjoy their meals. "But certainly not snail porridge," assures Dr Methven.

It seems a long way from sniffing at brown glass bottles, but we may just hear "Umai!" coming from hospital wards in a few years' time.

A matter of taste: Umami the world over

USA Tomato ketchup
Vietnam Nuoc mam fish sauce
Australia Vegemite
China Soy sauce
Thailand Nam pla
Europe Cheese, particularly Parmesan and blue cheeses
Italy Ham, particularly cured such as Parma and pepperoni
UK Worcestershire sauce, Marmite, Bovril, bacon, asparagus
Germany Sauerkraut
Japan Miso, soy sauce, dashi
South America Tomatoes, fish soups