Decoding Deliciousness: The Science Behind Flavor
Issue 13, Volume 113
By Vinson Chen
What’s your favorite food? A slice of cheesy pepperoni pizza? Or maybe a super sweet chocolate cupcake? No matter what you’re eating, it will have a distinct flavor. We eat thousands of different foods across our lifetimes, yet we are able to differentiate between them. When you eat a cupcake, it tastes nothing like pizza … but how is that possible?
The five basic flavors are sweet, sour, salty, bitter, and umami––which is described as savory and meaty. You may be wondering why spicy isn’t included as one of the basic flavors. We often consider spicy as a flavor, but in reality, it’s simply a type of pain. The sensation of spiciness is produced when capsaicin, a chemical, binds to pain receptors—not taste receptors—on your tongue. The pain receptors communicate to the brain via neurons, resulting in the hot feeling on your tongue that you get when eating spicy food.
It’s a common misconception that each bump on your tongue is an individual taste bud; in truth, the bumps on your tongue are called papillae, and they each contain multiple taste buds. Papillae add extra surface area to the tongue, which makes it easier for food to interact with the taste buds. Taste buds are groups of taste receptor cells that have extremely sensitive microvilli—tiny hair-like structures—on them. These microvilli have receptor proteins on their ends that are able to sense food and communicate its flavor to the brain. Taste buds are replaced about every two weeks, which is why when you burn your tongue on hot soup, the recovery time is usually 10 to 14 days. Adults have an average of about 10,000 taste buds but lose many, as fewer buds are replaced over time.
Microvilli on taste receptor cells are able to distinguish between different flavors. Your saliva breaks down food into molecules that bind to receptor proteins on the microvilli. Different molecules result in different flavors communicated to the brain. For instance, sweet foods contain carbohydrates such as fructose, sucrose, and lactose. Salty foods contain mineral salts, namely sodium chloride, while sour foods often contain acids such as acetic acid or citric acid. Bitter foods often contain alkaline molecules such as caffeine and umami foods often contain salts like monosodium glutamate. For example, grapefruits contain large amounts of sucrose, citric acid, and an alkaline molecule known as naringin, which combine to give the citrus fruit its signature sweetness, sourness, and bitterness. Each receptor protein has a specific shape that only binds to certain food molecules, specializing in only recognizing one flavor. Once a food molecule binds to a receptor protein, neurons send signals to the brain communicating the flavor associated with that receptor protein.
Logically, it would make sense for your tongue to be the body part solely responsible for flavor. However, your nose actually plays a huge part in what you taste. In fact, smell is responsible for approximately 80 percent of a food’s flavor. That is why when you walk into a candy store, even though you are not actually eating candy, you can imagine those sweet flavors.
The process through which your nose contributes to flavor processing is called retronasal olfaction. Your nose contains several million neurons known as olfactory sensory neurons (OSNs) in each nostril. When you chew, the odors from the food are forced up your nose. Hair-like structures on the OSNs called cilia detect the odor, and the OSNs communicate the flavor to the brain by activating a certain pattern of neurons. The flavor sensed by your taste receptor cells is combined with the activation of neurons from retronasal olfaction to produce a coherent flavor. This explains why one of the common symptoms of COVID-19 is loss of taste caused by nasal congestion, which inhibits the effectiveness of retronasal olfaction.
Eating is often considered a mundane task, but the world of flavor is far more intricate than it may appear. Flavor perception combines the extremely sensitive, specialized cells in your nose and mouth to recognize and differentiate between thousands of different foods. Whether it’s a chicken over rice from the halal cart, a Big Mac from McDonald’s, or the school’s mozzarella sticks, the taste of Stuyvesant students’ favorite lunch items are only made possible by their noses and tongues—the masterminds behind deliciousness.