TASTE, THE BIG DIVIDE

There seems to be a consensus with food: top restaurants are filled with people saying the cooking is marvellous. But every now and then you eat something you’re not keen on, only to find someone else loves it. Is our sense of flavour shared or is it subjective? Dr Len Fisher reveals how genetics, culture and experience influence more than you might have thought.

In Los Angeles there’s a chef who has no sense of smell. 20-year-old Adam Cole, of barbecue restaurant Maple Block Meat Co, can detect the five basic tastes on the tongue (sweet, sour, bitter, salt and umami) but aromas – estimated by some to constitute around 80 per cent of the flavour experience – elude him.

Adam’s condition, called anosmia, is genetic, and he’s at the extreme end of the anosmia scale. He uses what other people tell him about his food to perfect his recipes. But we all have anosmias of some sort. A substantial proportion of the population, for example, can’t smell androstenone, a major contributor to the smell of truffles. I can’t, for one. Which saves me a lot of money in top restaurants, because I can skip the expensive truffle dishes.

On the other hand, I rather like celery, where androstenone is also a major aroma component. So maybe it’s not that I can’t smell androstenone, but that I perceive it differently. Our olfactory epithelium (a postage stamp-size area at the back of the nose where we detect aromas) has around 400 receptors for different classes of odour. They work by a combination code that’s like a keypad numbered 1-400. Let’s say, for example, odorant A is recognised by receptors 3, 244 and 377. Odorant B is recognised by receptors 10, 244 and 301. The brain can easily detect the difference between the two combinations of numbers. The possible number of outcomes is mind bogglingly high.

THE GENETIC ARGUMENT

Odour receptors are encoded by our genes so genetics play a large part in how the receptors and the code function. Among those who can smell androstenone (about 70 per cent of the population), some describe it as being like a combination of sandalwood and vanilla, while to others it smells like rancid urine. These differences in perception correlate strongly with genetic differences in each person.

Back in 1931, the DuPont chemist Arthur Fox was transferring a white powder called phenythiocarbamide (PTC) when some of the dust flew into the air, and a colleague commented on how bitter it was (lucky it wasn’t also poisonous!). But Fox was puzzled. He could taste nothing – he was taste-blind to it. If you hate cucumber sandwiches, you’re probably one of the 70 per cent of the UK population who can taste the bitterness, because cucumbers are loaded with PTC.

Which makes you wonder why cucumber sandwiches are such an integral part of a traditional high tea.

The accidental discovery of taste-blindness was just a start. Sixty years later, Linda Bartoshuk from the University of Florida revisited Fox’s work and discovered that not only did some people have stronger reactions to PTC, but they also had stronger reactions to all kinds of tastes. And so the concept of the supertaster was born.

Supertasting is thought to be associated with a particular gene (TAS2R38, if you really want to know) but genetic differences aren’t the only reason why we all seem to taste things differently. Experience also plays a part.

INFLUENCED BEFORE WE’RE EVEN BORN

Our reaction to particular flavours begins in the womb. One experiment found that young children were more likely to enjoy eating carrots if their pregnant mother drank carrot juice. The same thing happened with new-borns whose mothers consumed anise-flavoured food and drink.

Cultural experience also matters. In a beautiful series of experiments at the Monell Chemical Senses Center in Philadelphia in the US, Pam Dalton and her colleagues checked out the ability of people to detect the smell of benzaldehyde – the cherry-almond aroma in Mr Kipling’s Bakewell tarts. People’s ability to detect the aroma could be dramatically enhanced if a tiny drop of saccharine solution was placed on the tongue. Conversely, a tiny amount of MSG on the tongue made the aroma harder to detect.

But that was with Western subjects. With Japanese subjects it was the other way around. Which demonstrates that our brains, and our memories and associations, have a lot to do with our ability to savour different foods. And everyone’s experience is different. This makes it rather difficult to describe that experience. In one study, French and Vietnamese panellists were asked to describe their perception of different dairy and soy-based yogurts. The description of the aromas differed wildly between the two groups. The Vietnamese, more familiar with soy products, used just a few words (raw soybean; soy milk; tofu). Whereas the French – bearing in mind Vietnam was for a long time a French colony – used twice as many words but avoided direct reference to soy, and even referenced non-food products (wood; earthy; chalk).

Research into food descriptors is still at an early stage. The food historian Barbara Ketcham Wheaton, honorary curator of the culinary collection at the Schlesinger Library at Radcliffe College in Cambridge, Massachussetts, is compiling a huge database. In the meantime, chefs such as Adam Cole must be aware that the same descriptor may mean different things to different people. The best we can do is to employ metaphors – ‘a touch of pineapple, perhaps?’ – but each of us smells pineapples differently depending on our sensitivity to the aroma components. As the saying goes: one man’s meat is another man’s poison. So don’t believe what the experts tell you… You are the judge.

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Your ventriloquist brain

How is it that we sense flavour in our mouths when most of the information comes via the nose? Research by Charles Spence and others suggests that the brain acts like a ventriloquist: it combines the taste and aroma perceptions, then transfers them to the oral cavity where we feel the physical presence of the food to create the whole flavour experience.

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Is taste all in the mind?

There have been many experiments to see how external factors affect our sense of flavour. Chef Heston Blumenthal made a beetroot jelly with tartaric acid to give a blackberry-like tartness. When he told a diner that the purple jelly was beetroot, they said it wasn’t nice. But when Heston said that it was really blackberry, the diner said it was actually delicious. But it really was beetroot.


By Len Fisher in "Delicious", UK, June 2018, excerpts pp.32-33. Digitized, adapted and illustrated to be posted by Leopoldo Costa.