The Chemistry of Coffee

Introduction

YouTube Video


  • Coffee is a brewed beverage that comes from the bean of the coffee plant. There are two species of coffee plant that is used in commercial coffee, the Coffee Arabica L. and Coffea Canephora. Coffee’s optimal growth region is between the Tropic of Cancer and the Tropic of Capricorn.

  • I chose my subject because I absolutely love coffee, and I have wondered what the composition of such a delicious beverage is. I also wondered how chemistry affects taste, brewing, and health benefits.

  • My life is affected by coffee because I drink it constantly, and it tastes fantastic.

Composition of ...

Per weight coffee is made mainly of polysaccharides. Polysaccharides are a type of carbohydrate. In unroasted coffee the second most common compound are lipids. Lipids are compounds that are mostly insoluble in water, things like fats and oils. In roasted coffee the second most common compound comes from caramelization, caramelization is a non enzymatic browning reaction that causes the oxidation of saccharide. One of the chemicals that many people associate with their cup of joe is caffeine. Caffeine is a purine alkaloid, and it’s chemical composition is C8 H10 N4 O2. Another of coffee’s interesting components are acids. Acids in coffee greatly affect the flavor of it and how it feels in your mouth when you drink it. Among the acids are acetic, citric, formic, malic, fumaric, and others.

Main Chemicals, Compounds, Components


The two main chemicals in coffee are polysaccharides and lipids.

  • Polysaccharides are a type of carbohydrate that are made of chains disaccharide or monosaccharide units. These are composed of mainly carbon hydrogen and oxygen. An example of one in coffee is Arabinose, which has a chemical formula of C5H10O5.


  • Lipids are water insoluble compounds that are esters of fatty acid chains. One of these lipids found in coffee are triglycerides, and coffee’s triglycerides are mainly esters of linoleic and palmitic fatty acids. Linoleic acid has a chemical formula of CH3(CH2)4CH=CHCH2CH=CH(CH2)7CO2H, which is an unsaturated fatty acid that has a melting point of -5ºC. Palmitic acid has a chemical formula of CH3(CH2)14CO2H, is a saturated fatty acid,  and has a melting point of 63ºC. The reason for the difference in melting point of palmitic acid and linoleic acid has to do with their shapes, linoleic is an unsaturated fatty acid which has a double bond between carbon and hydrogen which causes a kink in it’s shape, while palmitic is a saturated fatty acid that does not have this double bond.
Chemistry's Role

Chemistry is involved in coffee because environmental factors in growing the coffee, such as humidity, pH of the soil, and location. Also the length that coffee is roasted changes it’s chemical properties, and it’s flavor. If one roasts it too short it is very acidic, and rather bad tasting, but when it’s properly roasted it has the chemical composition that many of us know and love. When coffee is roasted, the beans go through the caramelization process. Caramelization is the process in which polysaccharides are oxidized, and it’s a non enzymatic browning process. The byproducts of caramelization are carmelen, which has a chemical formula of C36H50O25, caramelan, which has a chemical formula of C12H18O9, and caramelin, which has a chemical formula of C125H188O80. Oxidation also somewhat changes the color of coffee, along with the beans slowly turning into charcoal.

Background Research

Coffee is grown in the bean belt which goes between the tropic of cancer and the tropic of capricorn. The bean is then taken and dried, where it is shipped to roasting facilities. These roasting facilities roast it, bag it, and sometimes grind it for you. Then it is your job to take the coffee, if it’s whole bean, grind it, but if not, roast it and enjoy.

Resources

http://www.jlhufford.com/articles/whatiscoffee.asp  

Chemical Composition of Coffee


http://www.chemistryviews.org/SpringboardWebApp/userfiles/chem/image/magazine/2010May/1005_espresso_table1.gif 

Chemical composition of coffee by weight.


http://www.sciencenews.org/view/generic/id/340733/title/Coffee_gives_jolt_to_life_span 

Health benefits of coffee


http://www.blackriverroasters.com/the-science-of-coffee/ 

explains lipids of coffee, caffeine a bit, and goes lightly into how the robusta and arabica beans are different.


http://www.vittoriacoffee.com/   

Has about coffee going from bean to tree, stuff about it’s grinding, it also mentions arabica vs robusta and the latitudes where they grow.


http://www.sweetmarias.com/coffee.other.robusta.php

This talked a lot about robusta beans, and what the difference is with them and arabica.


http://www.rpi.edu/dept/bcbp/molbiochem/MBWeb/mb1/part2/sugar.htm

This talked about sugars and polysaccharides.


http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/lipids.htm

Lipids


http://www.scienceofcooking.com/caramelization.htm

information on caramelization


http://lifehacker.com/5986506/the-science-behind-coffee-and-why-its-actually-good-for-your-health

Coffee’s health effects.


http://www.wired.com/science/discoveries/magazine/17-10/st_coffee 

What’s inside coffee


http://www.coffeeresearch.org/science/sourmain.htm 

acids


http://www.britannica.com/EBchecked/topic/15672/alkaloid 

Alkaloids


http://0.tqn.com/d/chemistry/1/7/-/B/1/arabinose.jpg 

visual reference for arabinose


Malliard Reaction.


About the Author
Matthew Hanson is a senior at Billings Senior High School. He loves coffee, playing clarinet, and spending time on computers. Next year he will attend Montana State University to study Computer Science and in his spare time he will drink lots of coffee.
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