A Cup of Coffee for the Chemists

Unroasted coffee beans beside fully roasted beans.

For as long as people have been working around the clock and undergraduate students have needed a little boost to get through a day’s lectures, coffee has been the go-to product. Coffee, and the caffeine that we extract from it, powers our 24-hours-a-day society. But while many students and professors worship coffee, a tasty cup of java contains plenty of chemistry as well. Coffee relies on its chemistry from the moment the bean is picked to the first sip.  Moreover, coffee’s most famous component, caffeine, plays a powerful role, even outside of that first cup of joe.

Coffee: A Brief History

If coffee could tell a story, it would talk about where it grew up, how it lived, and how people have consumed it over the years. Before coffee became the familiar hot beverage we now know, African tribes took the actual berries of the coffee plant and mixed them with fats to make special spherical-like energy food, like a proto-energy bar. Further coffee consumption came about when Islam forbade alcohol, allowing coffee to become the substitute drink of choice. From the Middle East, coffee spread to Europe by means of one tree stolen by a Dutch trader.  From that one tree came much of the coffee grown around the world today.

The spread of Arabica and Robusta strains of coffee From: http://www.nhm.ac.uk

Preparing the Beans

Coffee “cherries,” ready for picking                      From: http://www.foodprocessing-technology.com

After being picked, the ripe coffee “cherries” sink and become pulped to extract the beans. The pulped beans are fermented in water for up to 36 hours, which allows the densest, most flavorful beans to sink and ferment in another tank. Coffee beans are dried on special patios with a small sample roasted for quality tests. Beans that pass the quality tests are shipped to  supermarkets, coffee houses, and  home brewers.

Once the beans have been extracted, they need to be roasted.  The beans crack twice during roasting, leading to the release of the aromatic oils that make up the well-known coffee aroma. The first crack of the roasting process is due to a breakdown of the sucrose stored inside the beans.  The process is endothermic, mainly due to the energy required to release the water.  However, once the water is driven out the process turns exothermic as the sucrose inside the beans breaks down into water and CO2.  As these gases are released, the cells of the bean burst, causing the first crack.  After the first crack, the beans are roasted further until the oils within the bean are released, leading to the second crack. Oils are released onto the surface creating the shine common to coffee prepared in the espresso manner.  You can see the changes involved in the entire process here:

Decaffination: How the Caffeine is Removed and Where it Goes

Many people prefer the taste of coffee without the jitters; decaf coffee. For more than a century, decaf has become a viable option for enjoying the distinct taste of coffee without the stimulating effects of caffeine. Despite its name, about 2.5% of the original caffeine content remains in decaf coffee. Nearly every type of decaffeination process involves soaking the unroasted beans in water to dissolve the caffeine, then using activated carbon (Swiss water method) or solvent extraction (ethyl acetate or methylene chloride/dichloromethane) to extract the caffeine from the soaking water.

How coffee loses its jitters, but keeps its flavor.
From: http://www.beannorth.com

Where the caffeine goes after it leaves the beans.
From: http://www.beannorth.com

The beans are then re-soaked in the now decaffeinated water to reabsorb the flavor compounds lost in the caffeine extraction. The leftover crude caffeine is recovered via evaporation and crystallization and sold to companies.

How caffeine gets out of the coffee and goes elsewhere in the world.
From: http://www.teaandcoffee.com

Caffeine extracted through the decaffeination process never goes to waste. Caffeine is found in many body washes, facial creams, eye creams, soaps, and even sunscreen which takes advantage of caffeine’s property as a vasoconstrictor. Caffeine may also play a role also in protecting the skin.  It is also used in many chemistry labs as a melting point standard.  This means we can enjoy the benefits of coffee whether we drink it, use it to remove the bags under our eyes, or calibrate our instruments with it.

Caffeine and the Body

With so much to enjoy about coffee, there are caveats that reinforce that classic adage of having too much of a good thing. Caffeine is classified as a stimulant that attaches to adenosine receptors in the brain and causes the release of adrenaline from the pituitary glands, along with an increase in dopamine, for a mood boost. A caffeine high is the result, which can either make someone feel jittery or give them the pick-me-up needed for that all-nighter. The increase in dopamine and lack of drowsiness can improve, temporarily, learning abilities such as memory, comprehension, reflexes, and mental clarity, with milder effects on the brain than drugs that work on the same sites as caffeine. These include cocaine, amphetamines, and heroin. It improves endurance (hence the International Olympic Committee’s ban on caffeine for its athletes) but accelerates digestion and therefore increases diarrhea. Moreover, caffeine is a drug, complete with consequences attached to a lack of use.  Symptoms include fatigue, irritability, lower energy, depression, and  headaches. Also drinking about 42 cups of coffee in one sitting will kill someone of average body mass. Coffee overconsumption can also lead to dehydration. The more coffee consumed, the greater the water loss as a result. Caffeine dehydrates due to its properties as a diuretic, the same reason why people have to urinate after drinking liquor or lemonade.

Coffee is a wonder of a thing. Now all I have to do is grab a cup and see what I have been missing.

Tyler Brisbin is a Senior studying chemistry at the College of Mount Saint Joseph in Cincinnati, Ohio. He finds chemistry the most fascinating of all the sciences and plays the  violin. After his undergraduate work his career ideas cross somewhere at the intersection of rhetorical questions and graduate prospects.

Looking for more on coffee?  How about how coffee grounds and plastic are being turned into fuel!


4 thoughts on “A Cup of Coffee for the Chemists

  1. Pingback: Caffeine, after being removed from coffee beans, looks just like mud and ends up in soap and sunscreen.

  2. Pingback: 2013, End of the Year Wrap Up |

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