How do we taste food?

When I was doing my bachelor I had a Vertebrate class and one of the things we had to learn (and were actually evaluated on) was the “taste regions” of the tongue. I remember very vividly that we had to do a drawing and identify each area. I did well on that test…but as it turns out, this whole taste regions is not real.
How then do we taste or perceive flavors? As matter of fact, the whole food perception is a mix of 3 different sensory modalities or senses: Taste off course (or gustatory), smell (olfactory) and touch (somatosensory). Today I would like to talk to you a bit more about this senses and how they interact in order for us to taste our food. 

Going back to the tongue, you’ve probably heard about taste buds. You can find them all over your mouth: tongue, cheeks and even in the upper part of your esophagus. This buds are the receptors that will identify the different stimuli that we associate with the 5 main type of molecules known as tastants: Salty, sweet, umami (that are usually associated with nutritious foods), bitter and sour (sometimes associated with potentially toxic or harmful). There are also other flavors that might be added to this list, such as fatty and metallic, but for now I will stick to the “big 5”. All of this tastants are detected by your taste buds, which in turn send the information to be identified.
Tastant molecules. From: Biochemistry 5th Edition. Berg, Tymoczko and Stryer.
The most simple of this molecules is a hydrogen ion (H+) and it’s associated with sour taste. Acids are rich on this ions as you may have guessed. For example, in sour gummies, it’s usually citric acid that is used to give the sour taste. After this we have other simple ions, and the most common on is the sodium ion (Na+) this time associated with a salty taste (salt’s formula is after all NaCl). Still relatively simple is the molecule associated with umami (or savory taste) is similar to an amino acid called glutamate (a constituent of protein) you have probably heard of monosodium glutamate (or MSG) that can be added to certain foods, making them more savory. A bit more complex are the molecules that gives us sweet and bitter flavors. I talked about sugars a couple of weeks ago, but just a refresher, carbohydrates have several OH groups and is the presence these that makes things taste sweet. Bitter flavors are even more diverse, and some can be associated with plant products that can be toxic. However, they don’t have a single structure.

However, we all know that sometimes food taste more than just salty or sweet. What about smoky (like chipotle pepper which I love) or earthy (some cheeses). Well, these and other “extra” flavors are detected with our nose (which is why sometimes when you have a cold, food tastes different). Some of this “nose flavors” will be detected before you have put the food in your mouth (orthonasal stimulation) and other you will only realize after the food is already in your mouth (retronasal stimulation). This is why some very pungent smells cause us to “taste” it in our tongues.

And finally we have the texture of what you are eating. I personally have a very hard time eating soggy stuff. A sandwich can smell delicious, but if it had too much sauce and the brad became soggy, the moment bite it I will have a small gag reflex (sorry, TMI) and just won’t eat it. Texture plays a huge role on our perception of food. Actually, it can be such an effect that it might take precedent over the smell part, just because it demands more attention from us. At the same time, it’s the touch (somatosensory) sense that allows us to perceive spicy food,
Capsaicin molecule. From Wikimedia.
since it’s extremely related to pain. So as much as I hate to admit it to my best friend, when we consume spicy or “hot” foods such as chili peppers, we are feeling pain produced by the compound capsaicin…I still like my food spicy, for the record. 

That is a simplified explanation of how we taste. There are a lot of other factors that can affect how a food tastes for you (the attention you are giving to your meal, what memories you associate with your food, what are you seeing at the moment of eating).

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