taster's choice

Over at Swans on Tea, Tom expounded recently on how cooking isn't "really" science, recalling a family holiday gathering where his grade school niece wanted to bake something for her school science project. For Tom, this bit of information "elicited a mental face palm." He has a point: what he's really objecting to is not cooking per se, but the blind following of a recipe/instructions, which isn't any more scientific than rote memorization of scientific facts. Science is a process, and Tom goes on to suggest a couple of ways to make baking more like "real" science: you know, making a prediction about what might happen if you change one of the ingredients, or combine them in a different, and then testing your hypothesis. As Tom says, "In any reasonably complicated experiment, something will go wrong, and it's the job of the scientist to figure out why and track down where the problem is." And he went to relate how he solved a problem with his spectroscopy setup.

With all due respect to Tom, cooking, done properly, is not about blindly following recipes: it involves a lot of prediction and testing by experiment to get a dish just right. The recipes just give you the basic framework. It's even more of a science these days, with the rise of molecular gastronomy (about which I blogged three years ago), sous vide (read Lee's take here), and other cutting edge techniques that combine technology with basic chemistry to create new dishes that appeal to our taste perception. There's probably half a dozen potential science projects there. For starters, there's just the basic chemistry that takes place when we prepare various foodstuffs. As Lee said,

Cooking is really a type of chemistry, dependent upon the reaction of molecules to the application of heat, as much as anything. Proteins, lipids, and complex carbohydrates break down and/or change their shape when they're heated. McGee ... is the author of On Food and Cooking: The Science and Lore of the Kitchen, which is a history of food and cooking, a technical manual, and a chemistry text that explains what happens to various foods when you cook them using different methods and temperatures. Many foods, McGee explains, lose flavor, color, nutritional value, and texture when you cook them at high heat. This is because heat increases the action of enzymes before it stops them. Enzymes are another type of protein that increases the rate of chemical reactions, like breaking complex, long-chain proteins into digestible bits in your stomach. This is what happens in cooking, too, to a lesser extent.

So cooking is definitely a science, drawing on chemistry and physics and basic biology/anatomy among other fields, not to mention engineering to come up with innovative preparation techniques. It's become so much of a science, in fact, that the University of Copenhagen is currently advertising for a professorial appointment in culinary chemistry, part of an ongoing effort to establish molecular gastronomy as a serious field of scientific study. Kitchens today in fine restaurants are as likely to use liquid nitrogen as more conventional ingredients to achieve unique shapes and textures.

You may have learned the basics of how we taste in school. Here's a refresher, courtesy of How Stuff Works:

Taste begins with sensation in the form of electrical impulses. Sensations, however -- responses to stimuli like pressure, light or chemical composition -- become perceptions like touch, vision or taste only when they reach the brain. In humans, the chemoreceptors that detect taste are called gustatory receptor cells. About 50 receptor cells, plus basal and supporting cells, make up one taste bud. Taste buds themselves are contained in goblet-shaped papillae -- the small bumps that dot your tongue. Some papillae help create friction between the tongue and food. Every gustatory receptor cell has a spindly protrusion called a gustatory hair. This taste hair reaches the outside environment through an opening called a taste pore. Molecules mix with saliva, enter the taste pore and interact with the gustatory hairs. This stimulates the sensation of taste. Once a stimulus activates the gustatory impulse, receptor cells synapse with neurons and pass on electrical impulses to the gustatory area of the cerebral cortex. The brain interprets the sensations as taste.

There are four basic tastes that can be detected by receptors on the tongue: sweet, salty, sour and bitter. Well, actually, there's a fifth one now, too. It was first discovered in the early 1900s by a Japanese scientist named Kikunae Ikeda, who investigated how we detect the unusual flavor of savory seaweed common in Japanese cuisine, and ended up isolating glutamic acid as a fifth taste (umami) that has its own separate receptor. His study on taste wasn't translated into English until 2002, which is why umami has yet to make it into school textbooks.

In truth, our perception of taste is even more dependent on our sense of smell -- as much as 80% of the tasting experience, in fact. That's because the tongue has 9000 taste buds; but humans have between 5 and 10 million cells or receptors for detecting smell, which is how we can make subtle distinctions between how different foods taste. A scientist named Francois Benzi first proposed that because smell is so important to how we taste food, that certain food pairings should work well if they shared the same major volatile molecules. He first experimented with jasmine and pork liver, since both contain indole -- success! It proved an excellent match, and the field of molecular gastronomy was launched. 

MG pioneer Hester Blumenthal, who runs The Fat Duck in England, built on this work and discovered that caviar and white chocolate are also a perfect match, since they share trimethylamine. There's now quite an extensive list of scientifically based flavor pairings, including such unusual combinations as carrot and violet; strawberry, celery leaves and mint; banana and parsley (or cloves); and salmon and licorice.

Our favorite restaurant is Alinea in Chicago, run by chef Grant Achatz, who excels at these sorts of flavor combinations. Every "course" is specifically designed to make you appreciate textures, flavors and unusual pairings of food ingredients in surprising and innovative ways. He even has to design his own dishware to serve some of his more unusual concoctions, like the delicate metal trapeze-like contraption on which he serves bacon with butterscotch paste and dehydrated apple. Another course is served atop a lavender pillow that slowly deflates as you eat the main dish, providing just the subtlest infusion of lavender without overpowering the other flavors. (Achatz had tongue cancer a couple of years ago and many feared he would lose his world-famous sense of taste; but doctors were able to beat back the cancer without resorting to damaging chemotherapy.)  

Even the amateurs are getting into the act. Martin Lersch, a resident of Oslo, Norway who holds a PhD in organometallic chemistry, writes one of my favorite blogs, Khymos. He started a regular feature called "They Go Really Well Together," wherein he and others passionate about experimenting with food and cooking compete to create innovative recipes based on unusual food pairings. The first such challenge was a doozy: garlic, coffee and chocolate. Garlic and chocolate have nothing in common, but they both share volatile molecules with coffee. The trick was to combine all three in such a way that no one flavor dominated too much, and thus achieve a perfect balance.

Lersch and his blogosphere buddies love food, and science, and have a blast experimenting with these unusual food pairings. As with any science, something inevitably goes wrong, and they finesse their inventive recipes over time, through trial and error. Take Lersch's dish pairing dark chocolate and smoked salmon (pictured above): he encased the salmon in an agar cocoa gel served with sugared slices of lime for garnish. Anyone who's had a really good chicken or beef mole knows that chocolate pairs nicely with savory meats, but smoked salmon? Apparently so.

Lersch ended up with something that worked on the taste front, but fell short in presentation. In particular, he struggled with the preparation of the layered agar gel. Among the lessons learned: "It's crucial that the next layer is poured while piping hot so that it can melt a little into the layer below. Because of agar's significant hysteresis the gelled agar must be brought up to around 80-90 degrees Celsius to melt." The layers also tended to stick together, and fell apart when he tried to get it out of the prep box. And he mused about what might happen if he replaced the hot smoked salmon with cold smoked salmon, concerned that it could change color and texture when the hot agar solution was added -- more chemistry. I eagerly await the outcome of his experiment to test that theory.

The point is, Lersch started with an hypothesis: that because dark chocolate and smoked salmon had certain volatile molecules in common, they would pair well in a dish. He then created an experiment (his own recipe) to test that hypothesis, and he had to solve numerous problems that cropped up during the preparation process. Then he wrote up the results, and outlined the next step for further study. I'm sure Tom would agree: that's the essence of science. I doubt we'll be seeing molecular gastronomy in grade school science fairs any time soon -- but we should certainly see cooking-related projects that go beyond merely blindly following a recipe.

Comments

[Stephanie Chasteen]

There has been an increased interest in the science of cooking lately, there are a ton of fun resources.
The Exploratorium has a website specifically on the science of cooking -- http://www.exploratorium.edu/cooking/
And look for "science" and "kitchen" or "food" on Amazon and a bunch of things come up.

And thank you, Jennifer, for not perpetuating the myth that the tongue has a taste map when you discussed taste! I discussed that on my blog a while back.
http://blog.sciencegeekgirl.com/2008/05/15/myth-6-your-tongue-has-a-taste-map/

[Partially Deflected]

Something I remember reading from my elementary school days. Experimenters added food coloring to mashed potatoes (I believe it was blue).
People who ate them blindfolded could detect no difference.
People who could see them thought they tasted strange.

I saw a more recent article on Mental Floss that explained why things taste so bad after you brush your teeth. Basically, a commonly used foaming agent, lauryl sulfate, has a side effect of turning up your sour and bitter taste receptors while turning down your sweet receptors.