#LEARNABOUT: VOL 8.1. The Science of Taste & Smell

Happy 2016 everyone! To start off another year of food, culture and learning at Midnight Rosewater, we decided to teach you something very ...

Happy 2016 everyone! To start off another year of food, culture and learning at Midnight Rosewater, we decided to teach you something very different today: SCIENCE!
To be more specific, we want to explain how our bodies sense, perceive and process taste and smell. Hopefully we can offer you a glimpse into your perception world, and show you what makes the things you eat and drink so diverse and great, and explain the mechanism behind your ever changing experience of food. We will hopefully all learn to appreciate the food we eat more!
Before we start, I like to thank Dr. Anastasia Zink (Ph.D. in Neuroscience) again for all the help with this article. Couldn’t have done it without you!

Let’s first clear out some terminology.

Sensation vs. Perception 

There is a difference between sensation and perception. To summarize the difference in one sentence, sensation is your body interacting with the environment and turning the interaction into information that could be relayed through the body; perception is your brain interpreting the sensory information.

Taste (Gustation) vs. Smell (Olfaction) 

At their core, taste (gustation) and smell (olfaction) are more similar than different. Both involve detection of environmental chemicals, both contribute to flavor, both have strong and direct connections to our most basic needs such as thirst, hunger, emotion, sex, and certain forms of memory. The true difference between taste and smell are the receptors used to sense (tongue or nose) and the neural pathways involved for your brain to perceive the information.

Clear? Ok. Moving on.

What do we taste?

Anything you taste, from a ripe apple to a perfectly seared steak, can be broken down to 5 fundamental taste categories: sweet, sour, bitter, salty, and umami.
You are probably familiar with the first four, umami is a Japanese word meaning “savory.” The umami class of taste usually refers to your tongue sensing the presence of amino acids and small peptides.
five basic tastes

Wait a second, why isn’t spicy on the list? We will get into this later, but the short answer to this burning question (pun intended) is that spicy is usually perceived as a temperature or pain sensation as opposed to a taste.

Why do we have taste?

We taste sweetness, saltiness and umami-ness because our bodies have an absolute requirement for carbohydrates (sugars etc.), sodium chloride (salt), and amino acids in our diet. We taste bitter and sour because most of the poisons are bitter and spoiled food usually goes sour: this is your body trying to protect itself.

What is flavor?

When you bite into that delicious salmon fillet and say “that tastes great!,” or when you take a sip of a freshly popped champagne (hopefully with hydrosols added to it) and say “emmmmm~delicious~”  what you actually mean to say is that it has great flavor.
Flavor is a combination of taste and smell along a few other sensory inputs, but mainly smell, and it is the perception of all of the sensations. Therefore, flavor is a creature of your brain.
Here's a flavor wheel of commonly described flavors (all rooting from the five basic taste categories).
flavor wheel

What affects flavor besides taste and smell?

Well, as said, most of the food’s flavor come from smell-- as much as 80-90% indeed. We know this because when you have a stuffy nose, your food always tastes extra bland. There are also some medical conditions in which patients lose their sense of smell (called anosmia). These patients eventually lose interest in food and often develop malnourishment and depression.
However, several other factors also influence taste and smell heavily:


At higher temperatures, molecules are more active and bump into things more frequently. What does this mean to a foodie? Higher temps increase the chance that a taste-y molecule, let’s say, a sugar molecule, bumps into it’s matching taste receptor. Every notice a mixed drink or soda get sweeter as it warms up? Yep. That’s because when it was cold, the sugar molecules were moving around less and interacted with fewer sugar receptors.
The compound capsaicin, found in peppers, stimulates the heat receptor in the same way actual heat does, therefore, spiciness is more of a temperature sensation, and in extreme cases, just like extreme heat, will cause pain.


In 2012, the company Cadbury received many complaints about its change of recipe, despite that the recipe hadn't been changed at all. What actually happened was that Cadbury changed its milk chocolate bars to a rounder shape, and that produced more-than-expected differences in taste among the consumers. Texture has a huge impact on how you perceive flavor mainly because that the geometric shapes of the food influence the release rate of the chemical compounds and aroma.


Color (or as far as packaging) also influences how you perceive flavor (it's all in your mind!). Ketchup tried to release a green version of its product (with the exact same recipe) years ago, and it wasn't successful because people reported that the green ketchup tasted more sour. If they close their eyes, however, they can't taste the differences.
Think green ketchup is weird? How does this black burger from Japan make you feel?

black burger

noise (ambiance)

We all know that music affects your mood, it turns out that it affects your food too! People tend to enjoy their meals more in quieter and more organized settings, and perhaps that is why there was never Kanye playing in the background when you go to a upper-scale steakhouse (nothing against Kanye though).

pressure and humidity

There is a scientific reason that your airplane food tastes so blah (aside from the fact that it's probably not very good to start with). At low pressure and low humidity, people's smell and taste actually becomes less sensitive, therefore we tend to enjoy our food much less. Not to mention that it's usually cold in the cabin. 

plane food usually tastes bland

ASAPThought had an experiment video that's very interesting. You can check it out here.

How do taste and smell actually work? 

With taste and smell, most of the sensing is done by taste and smell receptors in the nose and mouth called chemoreceptors. These chemoreceptors are responsible for detecting volatile molecules that are dissolved in food and drink as tastes or suspended in the air as smells. Other sensory qualities like temperature and texture are detected by special receptors that respond to heat and pressure. The brain then interprets the sensory information it received from your skin, tongue, and nose and creates a cohesive representation.
Recognizing what something is and whether you’ve had it before (and if you like it!) requires multiple parts of your nervous system work together. Some parts of the nervous system  recognize the :what" and assign a label; while others recall previous encounters and add an important emotional component to the experience (more on that in the next issue!).

How does the perceived information reach the brain? 

Sensory information from the face (the nose, tongue, or skin) is carried to the brain by cranial nerves. There are 12 (or 13 if you are a shark) cranial nerves; each with a special job. To keep track of them, they are referred to by number or roman numerals. They also have special medical names but we will stick with the numbers today.

cranial nerves

Smell is detected by Cranial Nerve I. Tastes and textures are picked up by sensory nerves in the tongue and mouth by Cranial Nerves V, VII, and IX. Other nerves, including V, VII, X, and XII are responsible for chewing, producing saliva, and swallowing properly.

olfaction pathwaygustatory pathway

The sensory information detected by cranial nerves is sent to the brain stem and then to an area called the thalamus before going to the cortex. The information can be accessed by other areas of the brain, including those for memory and emotion. Any previous experiences you’ve had with that food, good or bad, can influence the way you perceive it today.

Does our taste change over time? 

The chemoreceptors in your nose and mouth are exposed to some pretty nasty stuff on the daily, including air pollutants. They are regularly bathed in acid and salt and other molecules that might be tasty but can be tough for a cell to take. Our body anticipates this turnover and produces a steady supply of taste and smell cells. Depending how quickly these cell die and are replaced contributes to variations in taste over time, including changes in flavor sensitivity. We probably all know someone who loves eating spicy foods enough to use chili sauce like a midwesterner uses ketchup. It’s partly because they have simply gotten used to it.

This is it for this issue. We will explore the relationship between smell/taste and memory next time in details!

(images: basic tastes:http://truetomybody.com/traveling-tongue-vitality-tip-35/; flavor wheel: http://trifectaexperience.com/BaristaBanterPost.aspx?id=30; plane food: https://www.flickr.com/photos/mrmystery/3956382954; cranial nerves:http://www.aboutcancer.com/cranial_nerves_081909.jpg; olfaction pathway: http://www.cbc.ca/news2/interactives/brain/smell-pathway.html; gustatory pathway: https://wine4soul.files.wordpress.com/2013/04/gustatory-pathway-cortex-in-insula-facial-and-glossopharyngeal-nerve-in-medulla-oblongata.jpg; black burger: http://static2.businessinsider.com/image/54202a65ecad041006be14e0-1024-512/black-burger-burger-king-1.jpg)

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