The tongue is king when it comes to identifying the things we are eating. While it is true that we eat with our eyes, that smell and aroma play a role, that we listen for the sizzle and feel the texture in the whole mouth, it is the tongue that is most brilliant at diagnosing the bite just consumed.
The Tongue Map
Dating back to the early 1900s, the tongue is often represented with a map that shows a virtual belt of flavor sensors around the edges, representing the ability to perceive different tastes in different areas of the tongue: Sweet up front, salty at the tip, sour on the back sides and bitter in the very back. Papillae, which cover the tongue, hold on to food and help move it around the mouth. They contain the tastebuds which perceive taste. Did you know you were born with 10,000+ taste buds!?!
More recently, scientists have determined that the map, created by a German scientist David P Hänig and embellished by Harvard Professor Edwin Boring in the 1940s, is a bit of an overstatement. Their renderings in the tongue map were more artistic than representational and lacked scale. While certain areas of the tongue are particularly sensitive to tastes and have a lower threshold for identifying them, the differences are more nuanced than originally thought. The two cranial nerves that carry this information from the mouth to the brain for interpretation are in the back of the throat and the front of the tongue. If the tongue map were absolute, damage to the rear nerve would preclude the perception of bitter and damage to the front nerve might eliminate the perception of sweets, but fortunately that is not the case.
The Five Tastes
What has not changed in newer research is that the tongue and its taste buds identify a variety of nutrients (sometimes warning of potentially harmful substances) to alert the body to both pleasure and sustenance, as well as danger. The four basic tastes - Sweet, Sour, Salty and Bitter – and the fifth taste – umami – help the body identify what is being consumed, and helped our ancestors survive, even if their understanding was more intuitive than informed.
* Sweetness represents the presence of sugars which are known to the body as a source of energy.
* The presence of sourness indicates acids. Spoiled foods are often sour, and this helped our ancestors avoid eating rotten food.
* Salty identifies the presence of sodium chloride an essential ingredient in balancing our electrolytes and maintaining hydration.
* And bitter, like sour, served as a warning, in this case to avoid toxic plants. Today we have learned to embrace a degree of bitterness, especially when combined with other tastes.
The Fifth Taste
These four tastes are quick hits on the tongue and do not last long, unlike the fifth taste umami. Umami is not only widely recognized across the entire tongue, but the perception also spreads as umami is consumed, and it lingers. Umami, or savory-ness, is essential in triggering a sustained release of saliva which is essential in digestion.
So, what does umami cue as it is consumed? Umami signals the presence of protein, via amino acids that are essential to survival. Amino acids are nutrient blocks essential to supporting all life and are an important guide to the taste of food. The most abundant is glutamate. Glutamate is found in many foods, like tomatoes and aged or fermented foods, such as cheese, miso and soy. It intensifies as the fruit matures, the cheese ages, or there is fermentation. And, when glutamate is paired with other compounds, like the nucleotides inosinate (appearing in meat and fish) and guanylate (found in dried shiitake mushrooms), the perception of umami is amplified, up to seven or more times. Consider how much more flavorful a classic bolognaise is when both meat and tomatoes combine than a tomato sauce alone; or how a risotto with both cheese and mushrooms will multiply the pleasure umami delivers.
This is the synergy that is umami.