In one of my mind wandering moments I got to wondering about tastebuds. The sense of taste evolved to protect us from poisons. As a rule of thumb, anything that tastes bitter is poisonous… given you eat enough of it. (pure cocoa is very poisonous to a dog but we would have to eat several pounds of it to have any effect)
First, the little bumps on your tonque are not your tastebuds. Those are papillae, shaped like a button mushroom, that stick out all over your tongue. Located on the papillae are the actual tastebuds, too small to be seen with the eye. Depending on your age you have about 5 or 10 thousand tastebuds.
Individual tastebuds have a lifespan on about a week and a half, about half that of most skin cells, before the cells die and are replaced. The older you get, the fewer tastebuds you have. Babies have tastebuds on their tongue as well as on their cheeks and the roof of their mouth. So it’s not so much that they are finicky eaters, as they are just overwhelmed by the mighty taste of mushed carrots.
There are five basic tastes. Sweet, salty, bitter, sour, and umami. You’ve likely never heard of the last one. It’s relatively new, first discovered a century ago in Japan but mostly ignored in the rest of the world until lately. Umami is like bacon. Savoury. Each flavour is experienced by a chemical reaction between certain compounds and your tastebuds. Sucrose causes sweetness, acid makes sour, saltyness is created with sodium chloride and the taste sensation is actually somewhat akin to electricity.
You may have heard that certain areas of your tongue are tuned to specific tastes. (the tip of the tongue for sweet and salty, the back for bitter, etc) This has recently been found to be untrue, or at the very least a gross over-simplification. Tastes can be tasted all over the tongue, though there are still certain spots that are stronger in different areas.
In the grand scheme of things, taste is actually a small part of the overall flavour sensation. The bulk of flavour is created with your nose, in the olfactory sensors. (why not just call them smellbuds?) If you have grated apple beside grated onion, you would be unable to tell the difference if you plugged your nose.
- Source: The Physiology of Taste by Prof. Tim Jacob, Cardiff University