The Chemistry of Chocolate
https://preview-archives.nbclearn.com/portal/site/k-12/browse/?cuecard=52212
General Information
Source:
Creator:
NBC Learn
Hoda Kotb
Resource Type:
Copyright:
Event Date:
Air/Publish Date:
02/12/2011
02/12/2011
Copyright Date:
Clip Length
Video Science Explainer
NBCUniversal Media,
LLC.
2011
00:05:02
Description
This NBC Learn video uses the process of chocolate-making to explain chemical reactions related to heat
and temperature, including melting point and the formation of crystalline structures. (Untempered
Chocolate photo: Courtesy of Katreece Montgomery)
Keywords
Chocolate, Heat, Melting Point, Cocoa, Cocoa Butter, Cocoa Bean, Temperature, Room Temperature,
Solid, Liquid, Viscous, Viscosity, Tongue, Taste Bud, Crystal, Seed Crystal, Crystalline, Tempering,
Caffeine, Theobromine, Tryptophan, "Mouth-Feel", Cacao Tree, Seed, Friction, Julie Yu, The
Exploratorium, San Francisco, National Science Foundation, Chemistry of Food, Food, "Chemistry Now"
Citation
© 2008-2015 NBCUniversal Media, LLC. All Rights Reserved.
Page 1 of 3
MLA
"The Chemistry of Chocolate." Hoda Kotb, correspondent. NBC Learn. NBCUniversal Media. 12 Feb.
2011. NBC Learn. Web. 5 February 2015
APA
Kotb, H. (Reporter). 2011, February 12. The Chemistry of Chocolate. [Television series episode]. NBC
Learn. Retrieved from https://preview-archives.nbclearn.com/portal/site/k-12/browse/?cuecard=52212
CHICAGO MANUAL OF STYLE
"The Chemistry of Chocolate" NBC Learn, New York, NY: NBC Universal, 02/12/2011. Accessed Thu
Feb 5 2015 from NBC Learn: https://preview-archives.nbclearn.com/portal/site/k12/browse/?cuecard=52212
Transcript
The Chemistry of Chocolate
HODA KOTB, reporting:
It is the reason chocolate is so widely seen as a token and expression of love, given as a gift to a
sweetheart or a treat to oneself. It is the reason chocolate is the most frequently craved food, worldwide:
Chemistry.
Yes, because of the chemicals in chocolate that affect the brain: caffeine, a stimulant. Theobromine, a
mood-lifter. Tryptophan, which helps the brain make serotonin, a happiness chemical.
But also because of the chemistry behind this: the smooth shine and rich texture of chocolate, especially
dark chocolate. The way it melts in your mouth, and tastes on your tongue. In fact, dark chocolate is a
great way to look at several basic chemistry concepts, starting with temperature, heat reactions, and
melting point.
JULIE YU (The Exploratorium): So today we are going to be melting some chocolate.
KOTB: Julie Yu is a scientist at The Exploratorium in San Francisco, who’s funded by the National
Science Foundation.
YU: Chocolate is composed of cocoa solids, cocoa butter and some sugar, and at room temperature, it’s in
a solid form. The melting point of a substance is the temperature at which it experiences a change, so it
will turn from a solid to a liquid.
KOTB: A change from one common state of matter to another. Why does chocolate’s melting point
matter to chocolate-lovers?
YU: One of the key reasons chocolate tastes so good to us is, in fact, its melting point. Our body
temperature is 98.6 degrees and the melting point of chocolate is somewhere around ten degrees lower
than that. And if you’ve ever held a chocolate bar in your hand for too long, you probably experienced
that it melted in your hand.
KOTB: And, that chocolate melts even faster in your mouth, which unless you’ve been drinking
© 2008-2015 NBCUniversal Media, LLC. All Rights Reserved.
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something cold, or out in the cold with your mouth open, is usually between 75 and 80 degrees
Fahrenheit, pretty close to the melting point of chocolate.
YU: As it reaches its melting point in the high 80 degrees Fahrenheit, you can see that it’s turning into this
nice viscous liquid.
KOTB: In chemistry, how viscous a liquid is, its viscosity, is a measure of a fluid’s thickness, and how
slowly it flows. As dark chocolate softens in your mouth, it starts to flow over your tongue, a pleasurable
sensation known in the food industry as mouth-feel.
As it melts, it moves over hundreds of taste buds and that is key to our perception of chocolate’s taste:
more than 1,500 flavor components have been identified in chocolate, making it one of the most complex
chemical mixtures known.
YU: The components of chocolate are cocoa solids, cocoa butter and sugar. There’s actually no water in
there. It’s cocoa butter as a liquid, not water.
KOTB: Heat isn’t just a factor in making chocolate solid or liquid, it is a major factor in making chocolate
itself from cocoa beans, seeds of the cacao tree that are fermented, dried and roasted, all processes that
involve heat or heated air. Roasted beans are ground-up, filtered, mashed and pressed into a cocoa butter
mix, usually in giant machines, which also produce heat.
YU: Through mechanical friction, rubbing the chocolate together, it gets finer and finer so that the
consistency is something that’s smooth in our mouths, and not grainy.
KOTB: What happens next is the reverse of chocolate melting in our mouths:
the smooth, liquefied cocoa butter mix will harden into chocolate as it cools, going from a liquid state to a
solid state.
YU: When chocolate hardens, what’s really happening is the cocoa butter that’s present is solidifying, and
the fat molecules that are inside the cocoa butter form a crystalline structure.
KOTB: But chocolate that cools and hardens too fast forms seed crystal structures that, like most
structures built in a hurry, are substandard, disordered.
YU: You can think about a pile of Legos that you collect, into a pile, and if you do it really quickly, they
will be every which way, and that’s kind of representative of a loose crystalline structure.
KOTB: Result: chocolate that’s dull, blotchy, soft. What works better?
YU: To actually join the Legos one by one into a tighter packed crystal structure.
KOTB: Which chocolate-makers do in a process called tempering, carefully controlling the temperature
and rate at which the liquid chocolate cools, so that what are called beta or Form 5 seed crystals form, in a
tight crystalline structure.
YU: And it gives us that nice consistency and shine that we like.
KOTB: Or love.
© 2008-2015 NBCUniversal Media, LLC. All Rights Reserved.
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