The Chemistry of Taste
Tuesday, May 25, 2010 Being a scientist by training gives me a unique perspective in the kitchen. You see, for me, the kitchen is like my own little laboratory. Chemical and physical changes take place, homogeneous and heterogeneous mixtures are formed, colloids are used, I mass things and measure volume, and I even time reaction rates. Sounds like a chemistry lab, right?
My own curiosity about why things work has led me to create a new section on my blog dedicated to educating my readers about the science of cooking. I think that is why I love cooking so much. Cooking is both art and science. It is my form of creative expression, yet it feels comfortingly enough like science. I promise to bring you enough information to be helpful and interesting, and I will try not to bore you with too much detail. So here goes the first topic!
The sense of taste is the result of a chemical reaction between compounds in foods and receptors in our tongues. Our taste buds on different regions of the tongue are sensitive to different types of tastes. You can think of it as a lock and key situation. Flavor molecules have specific shapes and fit into receptors on the tongue that are shaped to receive them. But that is not the end of the story. These flavor bearing molecules must be released from the food by being dissolved in something. That’s the tricky part. First, let’s learn a little bit about molecules.
Most of the things we eat were alive at some point in their past. It doesn’t matter if you’re a vegetarian or an omnivore, you’re eating something that is a carbon-based life form. The simplest form of carbon-based molecule is the hydro-carbon. Putting it simply, a hydro-carbon is a chain of carbon atoms that is surrounded by hydrogen atoms. The hydrogen outer layer acts like a shield against polar molecules such as water. In a water molecule, there is a positive charge center near the Hydrogen end and a negative charge center near the Oxygen end. So it has two poles: + and -. Because simple hydrocarbons are not polar molecules, they cannot be dissolved by a polar molecule. Oil and water don’t mix. So these flavors need the presence of fats or oils to dissolve them and release their flavors. Did you ever wonder why “low fat” versions of your favorite foods were severely lacking in flavor? If there is no fat or oil in the food to release the fat-soluble flavor molecules, you will not be able to taste them.
Now there are some more complex hydrocarbons that are not simple chains. They contain benzene rings and other structures and are known as aromatic hydrocarbons due to their strong odor. This tends to give a slight polarity to the molecule, so it will be partially dissolved by water. Like dissolves like. Vanillins, including Vanilla of course, are a prime example of this type of molecule. They are light molecules, so the readily evaporate and are easily smelled. They are also dissolved by water so are easily tasted.
Most easily dissolved by water are polar, inorganic compounds such as salts. The salts dissociate, or break, into separate ions when dissolved in water. They are easily delivered to receptors on our tongues to be tasted. That’s why food that is too dry is less flavorful than moist food.
And yet there is another way to release flavor. Some molecules are soluble in alcohol. Molecules like capsaicin are soluble in oil and alcohol. Capsaicin is a fatty molecule with a long hyrdo-carbon tail that repels water. Capsaicin is responsible for the burn when you eat hot peppers. Capsaicin opens a door in the cell wall that allows Calcium ions to flood in. That triggers a pain signal which is passed to the next cell. The same thing happens when cells are exposed to heat. The solubility of capsaicin explains why drinking water after eating a hot pepper doesn’t work. If you want to dissolve the molecules and wash them away, have a cold beer or margarita. Or better yet, have a glass of milk. The casein in milk loves fat and will wash the fatty capsaicin molecules away.
Cooking meat with alcohol is a common and popular practice for this very reason. Using red wine when cooking beef will dissolve flavor molecules that are untouchable by water and oil. That’s why the depth of flavor is so shocking (and delicious). Glutamic acid is found in beef and in many other flavors that pair well with it. When two of these flavor compounds are together, the flavor effect can be eight times as intense. These flavors include aged cheeses, red wine, bacon, mushrooms, soy sauce, and tomatoes to name a few. Think of your favorite dishes that pair some of these ingredients. Alone, they are good, but together they are fabulous. It’s all in the chemistry of taste!
I hope I've given you something to think about as you cook. Play around with water-based liquids, fats, and alcohol in your cooking and see what delicious flavors you can unlock!
Keep lovin' and keep cookin'.
Reader Comments (3)
Very interesting reading. You know, I bet a lot of people don't know this or have never even heard of the science behind unlocking flavors in this manner. It is interesting how somethig that you may have eaten a million times before can have a completely different flavor potential simply by unlocking the molecules with say an alcohol or certain fat. Thanks for sharing! ;)
VERY interesting. As one ages, taste buds loose some of their sensitivity. I am looking forward to adjusting my cooking in some of the areas you write of. Hopefully, food will become a bit more flavorful to me! Thanks for this wonderfully educational read!
Janice, I'm glad you liked the article. It is interesting how our tastes change with age. I'm trying to convince my 8 year old that he will like different things as he gets older. It's a tough sell! :)