What the heck is flavor?

As an introduction to my blog and my prelude into the world of blogging, I decided to expand upon something within the realm of food science that relates to everyone: the mechanism of flavor. The neat thing about taste is that although we all have different preferences, the physical process that our bodies use to convert the different molecules and ions of an assortment of foods into something that we recognize as “pizza!” or “liver…” is, for the most part, the same across all humans! (Note: it gets a little more complicated when we include super-tasters and people with taste disorders.)

How you experience a food or drink begins with a process called gustation – a fancy word for taste. Taste is a highly orchestrated sensory event that combines all the chemical and physiological aspects of sensation, transduction, and perception. It’s much more complex than meets the eye (or mouth!) and interweaves many stimuli to create an experience that we call, flavor.

As you might guess, it starts with the taste buds. But did you know that within each individual taste bud inside your mouth, there are 50-100 taste cells that contain special “hairs” to detect all five taste sensations? These hairs, called microvilli, increase the surface area of the cell to allow it to take in sweet, salty, bitter, sour, and umami (and rumored to be another taste, olegustus) molecules that lead to the sensation of one of millions of different foods [1],[2].

In the case of sweet, bitter, and umami molecules, they bind to a receptor protein within the membrane of the microscopic taste cell. Salty and sour taste molecules, or ions, travel through transmembrane protein channels to reach the taste cell. Once this occurs, a series of events unfold which ultimately leads to the sensory message being sent to the brain.

Flavors of food and other substances are also created through gustation’s two other “sister senses,” smell (olfaction) and even nerve stimulation from pain or temperature change (nociception).

Foods like wasabi and horseradish aren’t sensory experiences but irritations! These foods stimulate the nasal passages and result in a burning sensation in the nose and throat, and watering eyes. When we eat chile peppers, we actually experience pain due to nociceptors in the mouth being triggered by a compound called capsaicin. The capsaicin activates this pain receptor and a message is sent to the brain resulting in an array of physical symptoms, such as increased heart rate and sweating.

wasabi… ice cream?

Maybe you enjoy cold, left-over pizza, but what about a cold egg omelet? Often times we associate certain meals with distinct temperatures. So, why does your favorite thin-mint cookie or sugar-free gum give you the shivers? Certain ingredients impart “cool” effects – such as sugar alcohols like sorbitol, xylitol, and maltitol or from substances like spearmint or menthol. They trigger specific ion channels within nerve cells that are responsible for signaling that you are experiencing cold! The same mechanism works for spicy foods like hot sauce that possess the ability to turn ‘on’ ion channels that are also activated by hot temperatures [3].

Ted-ED Video on the “science of spiciness!”

The gustatory and olfactory systems are both alike in that they are both chemical senses, operating using a chemosensory system to extract stimuli from the environment and make meaning out of it, unlike the other senses, which primarily use mechanoreceptors and photoreceptors to transduce physical stimuli into a response.

In fact, it’s easy to confuse smell for taste. It happens all the time – for example, the odor of vanilla is often associated with sweetness. This is why vanilla extract is often added to baked goods, as its aroma intensifies our perception of sweet [4]. Odor of a food also amplifies how we experience texture, because the two brain cortices that regulate sensation and perception for smell and touch—the olfactory and somatosensory—are linked. Creamy foods are perceived to be sweeter than their gritty or crunchy counterparts, regardless of whether sugars are present. However, though there are around five or six basic tastes that humans can distinguish, like “sweet,” scientists have predicted that we can smell anywhere from 4,000 to 10,000 different odors [5]! That can lead to a lot of different flavors. Reception and transduction of olfactant molecules occurs in a similar series of events that taste molecules do; the molecules bind at a protein receptor site on olfactory nerve cells. A cascade of intracellular events occurs, and the signal message is routed directly to the forebrain where they are “decoded” and recognized as a particular smell [6].

These sensory qualities  coupled lead to the emergent property of flavor, but how a food is perceived by a person relates to a few other factors, including its’ presentation and how it sounds, as well as one’s individual psychology. In part two, I’ll divulge more delicious secrets on the experience of eating!

[1] “Molecular Basis for Taste — Tastant Molecules.” Molecular Basis for Taste — Tastant Molecules. 1999. Accessed December 15, 2015. http://www.edinformatics.com/math_science/science_of_cooking/taste_molecules.htm.

[2] Running, Cordelia A.; Craig, Bruce A.; Mattes, Richard D. (July 3, 2015). “Oleogustus: The Unique Taste of Fat”. Chemical Senses 40 (6). doi:10.1093/chemse/bjv036. Retrieved December 14, 2015.

[3] “Molecular Basis for Taste — Tastant Molecules.” Molecular Basis for Taste — Tastant Molecules. 1999. Accessed December 15, 2015. http://www.edinformatics.com/math_science/science_of_cooking/taste_molecules.htm.

[4] Sakai, N., T. Kobayakawa, N. Gotow, S. Saito, and S. Imada. “Result Filters.” National Center for Biotechnology Information. June 1, 2001. Accessed December 15, 2015. http://www.ncbi.nlm.nih.gov/pubmed/11565908.

[5] “TASTE AND SMELL.” Taste And Smell. Accessed December 15, 2015. http://dwb.unl.edu/Teacher/NSF/C10/C10Links/ericir.syr.edu/Projects/Newton/11/tstesmll.html.

 

[6] Hutchins, Max. “Chemical Senses: Olfaction and Gustation (Section 2, Chapter 9) Neuroscience Online: An Electronic Textbook for the Neurosciences | Department of Neurobiology and Anatomy – The University of Texas Medical School at Houston.” Chemical Senses: Olfaction and Gustation (Section 2, Chapter 9) Neuroscience Online: An Electronic Textbook for the Neurosciences | Department of Neurobiology and Anatomy – The University of Texas Medical School at Houston. 1997. Accessed December 15, 2015. http://neuroscience.uth.tmc.edu/s2/chapter09.html

 

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