The Chemistry of Coffee

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

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

Malliard Reaction.

About the Author