Anyone for crab ice cream?

Crab ice cream may seem a bit fishy, but it's all a question of taste, says Sanjida O'Connell

Guardian

Thursday July 5, 2001

 

Heston Blumenthal , head chef and owner of The Fat Duck in Berkshire, is serving crab ice cream with risotto and mustard ice cream with red cabbage gazpacho. He argues that any customer who complains at the odd choice of accoutrement is not objecting to what the crab ice cream actually tastes like; instead the diner subconsciously expects a sugary dessert. This is exactly what food scientists are now discovering about food - our perception of taste is mediated by the brain as much as by our taste buds.

We are the only species on the planet that doesn't eat just to survive. "Flavour is the way food communicates with us," says Dr Anthony Blake, vice president at Food Science and Technology at Firmenich, a perfume and flavour company based in Geneva. "On a simplistic level, if it tastes good we eat it and if it doesn't we spit it out. But humans are not content with simplicity."

Just as we turn words and sounds into poetry and music, we turn the appreciation of food into the art of gastronomy. We've been doing it for years. At Lixus in Northern Morocco is the oldest example of a flavour factory: a pit in which anchovies were left to decay and fermented to make garum, a fish sauce. Worldwide trade has dramatically altered our perception of flavour - oranges are not native to Spain, risotto is made with rice originally from China and the rhubarb fields of West Yorkshire were stocked with plants brought over by Arabs. As Dr Blake says, "It's hard to imagine Indian or Thai cuisine without chillies, Hungarian goulash without paprika, satay sauce without peanuts, or ice cream without vanilla, but that was food before the 15th century."

Taste buds in our mouths detect whether food is sweet, sour, salty or bitter; we may have a fifth taste bud which detects MSG (monosodium glutamate). The texture of food, its crispness or sliminess, is conveyed from the mouth to the brain via the trigeminal nerve. We can tell how spicy food is because the capsaicin in chillies stimulates pain cells. But most of our experience of food comes from its aroma.

"It's the difference between apples and apple pie; aroma compounds make all the difference," says Dr Rob Linforth from the flavour and food sciences lab at Nottingham University. However, what we actually think we can smell (and thus taste) is not what we actually smell - our perception is mediated by the brain. What we find palatable is determined at an early age. "To Marmite eaters of the world, Marmite is delicious," says Dr Blake, "but to Americans it's disgusting." He gives the reverse example of wintergreen, widely used in soft drinks such as root beer - it stinks of Germolene, and to most Europeans, the thought of drinking it is repellent.

It is not only our likes and dislikes that are learnt, but our ability to taste certain substances. Dr Paul Breslin, from the Monell Chemical Senses Center in Philadelphia, gave volunteers benzaldehyde, which smells of bitter almonds (and is present in cherries and plums), below a normal level of detection, along with a similarly small amount of MSG. The panel lists could detect neither flavour apart from the Japanese member. Europeans associate plums and cherries with sweetness, but the Japanese are fond of pickled plums which are rich in MSG. This experiment suggests that the association between tastes and aromas, and the ability to detect certain flavours, are responses learnt in childhood.

This discrepancy between what we are tasting and what we think we are tasting prompted the flavour scientists at Nottingham University to search for an objective "flavour-meter". "Creating the machine was a bit of a eureka moment," says Dr Linforth. The machine, known as Affirm, measures the amount of aromatic compounds in the breath as a person eats. It is incredibly sensitive and it can detect 10 parts of an odour per billion parts of air in a tenth of a second. Affirm was funded and built by Firmenich; Dr Blake says the most surprising finding was that "the nose doesn't measure the absolute level of flavour, it measures the change. It's so obvious really - if you go into a smelly room, you hold your nose and you can't smell, yet the air and those smell molecules are still in your nose."

This is a hugely important finding for the food industry because it shows that the overall amount of flavour is not as important as the rate of flavour change detected by the brain. As the researchers discovered, the nose adapts to a persistent flavour in 80 seconds and within five minutes loses the ability to smell that flavour at all - this is why chewing gum appears to lose its taste even though there is as much peppermint flavour in the nose when the gum chewer started chewing as there is two hours later. This is the reason for Ben & Jerry's popularity - the ice cream contains chunks of surprising ingredients, such as raw cookie dough. Their ice cream capitalises on the brain's ability to respond to sudden changes in flavour. "The general rule of thumb in the food industry is to mix everything in," says Dr Blake, "but this research shows that we should be creating hot spots of flavour."

Affirm also indicates that the combination of flavours is important. For instance, marmalade on dry toast has an intense flavour, but a thin layer of butter absorbs 90% of the marmalade aroma compounds. Dr Blake advises eating thick-cut marmalade with its intense bursts of flavour from the peel if you're going to butter your toast. Manufacturers of low-fat foods are very interested in Affirm as they hope it'll help them develop foods that taste good despite the reduction in calories. What the latest results from Affirm show, says Dr Linforth, is that, "People are good on quality, not on the intensity of aromas."

In other words, as long as food tastes OK, it's better to concentrate on the texture. It's very easy for most of us to detect poor quality food, particularly in ice cream, says Dr Peter Barham, a physicist and food science expert from Bristol University. Ice cream is essentially fat and sugar embedded within ice crystals and air. Fast freezing and vigorous beating creates ice crystals which are smaller than air particles - if the crystals are larger than the air the ice cream feels gritty. Heston Blumenthal 's ice cream should never be gritty - it is made to order and only kept for 30 minutes so the ice cream doesn't have time to grow large ice crystals. As for its flavour, Agnes Marshall, champion Victorian ice cream maker, led the trend for savoury recipes, such as asparagus and fish. Sweet ice cream became popular here between the wars when Italians settled in the UK and set up ice cream parlours. But back in Italy you'll get the real Mcoy - parmesan ice cream.