When we talk about flavor, we typically think only of our tongues. But, flavor is comprised of two sensory systems: the tongue, where we perceive taste, and the nose, where we perceive aroma. And, thanks to our bio-diversity, we all sense things a little bit differently, which often leads to a wide range of opinions on your favorite beer.
The tongue is one of the systems we humans use to push ourselves towards desirable foods and away from dangerous ones like rancid food or poison. The sense of taste is so important that it has three paths to the brain in case there is a failure on one of those paths.
The tongue has about 10,000 taste buds, with a few also sprinkled throughout other parts of your mouth, such as in your cheeks and esophagus. Each taste bud has between 50 and 100 taste receptors that recognize certain molecules in food. And, as we age, the number of receptors decline; this is why many elderly have a lack of appetite and lack of interest in food; this in turn leads to fragility and poor health.
Back in the 19th century we used to think that 5 different areas of the tongue perceived the different basic tastes, but science has since proven that most of the tongue is perceptive to all of the basic tastes: sweet, sour, salty, bitter, and umami.
Sweet - Sweet receptors were used in evolution to point us towards things that had a lot of nutritional value. In the modern era this has proven troublesome for our bellies as a sweet taste is always available and our brains still think we should have this.
Sour - The ability to detect a sour taste allows us to detect acidity as well as ripe or spoiled food.
Salty - Salt plays a crucial role to many cellular processes which require sodium and potassium. And let's face it, salt tastes really good.
Bitter - Despite the fact that we like hops, bitter senses are used to avoid potentially dangerous toxins like cyanide. But, bitterness is a rainbow and there may be more at work in the brain.
Umami - Translates to "pleasant savory taste" in Japanese and its job is to point out savory flavors, which are recognized through receptors looking for glutatmate, which is an amino acid used to synthesize protein.
The tongue can also perceive other sensations that are not lumped in with the basic tastes: spiciness, pungency, coolness, numbness, astringency, metallics, calcium, fat, temperature, and starch.
But, taste is only one half of the flavor equation, as our noses also play a crucial role, as we'll find out next time.
Sources: Randy Mosher's Tasting Beer, Brain Blogger