Learning from the Human Tongue
Making a solution from foods to measure their flavor
The newly developed taste sensor is based on a completely different approach. This time, the idea was to imitate the way the human tongue perceives taste, and to convert the tastes that people experience into digital information. The rough surface of the human tongue is covered with "taste cells" that are sensitive to different kinds of flavors. When you put food in your mouth, flavor particles in the food come into contact with the taste cells on your tongue. This causes a chemical reaction that sends a message to your brain. Your brain interprets the signal as a particular flavor. This is what gives us the sense that what we are eating is sweet, bitter, or sour.
The new taste sensor recreates these human taste cells artificially. In the tongue, a chemical reaction takes place when the flavor-giving substances in food come into contact with the proteins and fats in the surface of the tongue. For the taste sensor, a similar chemical reaction was achieved by dissolving fats in a substance called polyvinyl chloride—a polymer also used in making plastic bags. (A polymer is a chemical compound made up of long strings of the same molecule group. They tend to be strong and flexible.)
There are five basic flavors: sour, bitter, sweet, salty, and umami, or savory. After a lot of research, scientists succeeded in developing a taste sensor that reacts only to these five main flavors. As well as measuring how much of these five flavors a substance contains, the taste sensor can also detect aftertaste. Aftertaste is the flavor that remains on the tongue after we swallow, and is crucial to the way we experience what we eat. This is what gives things like thick, rich soups their distinctive taste.
How the tongue detects flavors