In the latest of our shortlisted entries to the 2011 Wellcome Trust Science Writing Prize, Jasmine Spavieri takes on a gastronomic journey.
It all starts with an apple pie. That fresh-from-the-oven baked crust, curling around the rich, succulent fruit. Steaming corkscrews of warmth bring the aroma to our nose, ringing bells of desire. Get to work salivary glands! Ready the battleground for a scrumptious engagement.
Success. We’ve managed to load the perfect ratio of pie crust to apple filling onto our dessert fork. A quick pitstop into the vanilla ice cream and we’re good to go. Oh, sensory jubilation!
A plethora of food molecules dissolve, each compound melting onto our taste buds, home of the taste receptors. Our gustatory system – the sensory system for taste – has evolved to help us decide whether our food is inedible or is worthy enough to be swallowed. Like keys on a piano, each receptor plays a specific note, with each note representing a different taste. A harmonious combination of ingredients will release Beethoven’s fifth symphony within your mouth.
But let’s return to our apple pie. As we chew the tasty morsel, sugars flow over our taste buds and find their match, the sweet receptors. Carbonyl groups from the sugars bind to the sweet receptors resulting in an electrochemical signal that travels to the brain, carrying a tantalizing delivery. This glorious chain of events is responsible for our perception of sweetness and for many a failed diet.
Again, let us not abandon our pie. In addition to the sugar, ascorbic acid from those juicy apples tickles our sour receptors. Hydrogen (H+) ions are found in all acidic food. They flow through the ion channels on the receptors and activate specialised sensors, which ultimately lead to the release of a neurotransmitter that signals the brain. The result is a sensation of quenching tartness that counteracts the sugary pastry. Well played, chef. What’s next on the menu?
How about a fifth taste? For years, the conventionally accepted tastes were sweet, sour, bitter and salty. However, at the turn of the century a mysterious new taste was identified by Kikune Ikeda of Tokyo Imperial University. It wasn’t until the year 2000 that researchers from the University of Miami discovered that the receptor for the fifth taste was activated by L-glutamate. This is an amino acid found naturally in fermented products like soy sauce, Worcestershire sauce and many meats and cheeses, it triggers a sublime savoury sensation. This fifth taste is known as umami, the Japanese word for ‘delicious’.
Most receptors in our taste buds made of molecules known as G protein-coupled receptors. These receptors need a specific protein to activate them, beginning a chemical cascade that eventually reaches our brain. More specifically, it is a protein known as gustducin that’s responsible for our perception of bitter, sweet and umami.
Intriguingly, gustducin is similar to transducin, a G protein naturally expressed in the retina. This suggests that taste may have evolved in a similar way to sight. Perhaps not so astonishing, given how our senses frequently interact. It’s no secret that the appearance of our food influences our perception of its taste, but texture and temperature also contribute to the overall flavour of a meal. This type of cognitive impact is the bread and butter of creative chefs like Heston Blumenthal, if you’ll excuse the pun. Anyone who is familiar with his lavish banquets is aware of how his meals tease all of our senses, including our sense of humour.
Chefs delight in confusing our taste buds, blending tangy acidic tidbits with mellow, sugary compounds. Sometimes it works, sometimes it doesn’t. Flavour fusions like cheddar and chutney or Italian basil and tomato, are fine examples of matches made in heaven. Cooking, like painting, is an art of many nuances. Physical chemist Hervé This has turned it into an exact science. A man who is equally dedicated to science as he is to casseroles, he coined the term ‘molecular gastronomy’, the science of cooking. In his laboratory at the Institut National de la Recherche Agronomique, he discovered the perfect temperature at which to cook an egg, 65°C, so that the yolk remains liquid as the white solidifies. Besides teaching us how to make scientifically delicious mayonnaise or poach an egg in whisky, he is passionately devoted to understanding the molecular mechanisms at work during cooking. So while his research may not cure cancer or baldness, it might help your next soufflé rise.
This is an edited version of Jasmine’s original essay. Views expressed are the author’s own.
Over the coming months, we’re publishing the shortlisted essays in this year’s inaugural competition.