A Short Course on Coffee


Andy J Miller

By: Karen Diep

What: Coffee
Category: Drink
Country of Origin: Ethiopia and Yemen
Quick Fact: Coffee has more aromatic compounds (1,000 identified volatiles) than wine.


We all know coffee. But does anyone really know coffee? To the average consumer, coffee is a very basic concept but to the true baristas and somms of coffee–coffee is a religion. Upon beginning my research for coffee, I did a simple Google search on “coffee.” What was the first link to appear? Starbucks. If there is something I want to accomplish after writing this article, it’s to convince all that there is much more to the world of coffee than just Starbucks.

Like any other food product, coffee is complex, unique, and undoubtedly a worshipped food. Coffee is universal and as ubiquitous as water. It is the most traded commodity right after petroleum and is the most consumed beverage–mainly by the world’s industrial nations but is grown by the world’s underclass (1). It has a colorful history but it does not live without its controversy. This article will cover the basics of coffee from the plant origins to harvesting, processing, roasting, brewing, and the modern concerns of coffee.

Coffee: Growing, Harvesting, Processing, & Roasting

Coffee comes a type of flowering shrub with the genus name Coffea. The two most popularly grown species are Coffea arabica and Coffea robusta. Coffee trees are evergreen and requires a specific climate that is moderate, located between a latitude of 10 degrees north and south of the  equator, and at an altitude of three to six thousand feet (or 910-1,830 meters). Similar to grapes used for wine, coffees grown at higher altitudes will produce denser beans that have more complex flavors. This is due to the fact that at higher altitudes, the coffee plants will concentrate more on growing their seeds and less on vegetative growth. As a consequence, however, the cherry yield will be much lower (2).


Coffee (Larry Jacobsen)

Coffee beans come from the red or purple “cherries” that the plants produce. Coffee beans aren’t actually true beans but seeds contained inside the cherries. In each cherry, there are two beans enveloped in a silverskin. Each berry is hand-picked and then sorted by color and ripeness and processed (either wet for dry) to remove the pulp and mucilage covering the silverkin and beans. The coffees then enter the dry mill stage where they are sent through a dry mill to remove the skin, parchment, and some of the silverskin. Afterwards, they are sorted again by color, density, and size (3). At this point, the coffee is called green coffee prior to roasting. The coffee is expected to be used within one year to capture its freshness and flavor.

Roasting involves a number of variables all of which are controlled to create the final desired product. Roasting the beans changes the beans both chemically and physically. As the beans roast, the beans loses moisture and therefore density but also increases in volume. Actual roasting occurs when the centers of the beans reach a temperature around 392 degrees fahrenheit or 200 degrees celsius–though the temperature varies depending on the beans’ density, moisture, and size (3).

The reaction that occurs during roasting is caramelization where the heat breaks down the starches turning the simple sugars brown and, consequently, the color of the bean to brown (4). During this time, the beans will develop more complex flavors and adjusting the parameters and methods of roasting will produce different results. Roasting at different levels will  produce lighter or darker beans. The beans are then graded as light, medium light, medium, medium dark, and dark roast. The darker the roast level, the greater the roast level that will mask the flavor of the bean itself making it difficult to distinguish the origin of the beans (11). Coffees with distinct flavors such as Ethiopian and Hawaiian are often roasted lightly to retain its distinct flavors.


Range of colors created by roasting (cyberiancafe.com)

A Note on Storing: After coffee is roasted, a countdown clock immediately starts and its flavor only lasts for a short window. Coffee connoisseurs will urge people to only purchase coffee in small amounts and replenish when necessary. As tempting as it is to buy in bulk, coffee is only good for a finite amount of time but it, like most wines, has a lifespan. After roasting, coffee will develop its flavor and become more complex after 9 days. After reaching its peak, its flavor will begin to decline and eventually become duller, less flavorful, and oxidize. Darker roasts have a shorter lifespan where they peak early and begin to decline in flavor after 7 days. Lighter roasts take much longer to reach their peak but once reached will eventually become stale. Grounds have even a shorter lifespan and ground espresso becomes stale after 90 seconds. Coarser grounds become stale after 20 minutes, which is why some stringent coffee roasters refuse to ground their coffee for their customers and recommend grounding coffee immediately before brewing (2).

Wet and Dry Processing


Fermenting cherries remove the silverskins (Gary Cass)

Wet (or Washed) processing involves pulping the cherries in a machine to remove the skin and then using water to soak the beans and ferment where afterwards they are washed to remove the mucilage surrounding the beans.

Dry (or Natural) processing requires drying the beans until they shrivel like prunes with the beans inside. They are then either left to be stored in their skins and can be stored for months or taken to be milled and hulled to remove the skins. Other types of processing include a hybrid of the two called pulped natural processing, is indigenous to Brazil. Here, the cherries are pulped to remove the skin but instead of being soaked and fermented, it is dried on tables.


Raking helps aerate the beans and remove moisture from underneath the beans (Dennis Tang)

Either process is often region specific. Areas where water is scarce, the farmers will use a dry process whereas regions where water is plentiful the farmers can use a wet process to remove the skins. Both have their pros and cons but the results of each affect the flavor profile of the beans. Below is a table of the flavor profiles that result from the type of processing:

Types of Processing and its Typical Flavor Characteristics (5,2)

Processing Type Flavor Characteristics
Wet or Washed Cleaner, brighter, fruitier, higher acidity, elegant flavors
Dry or Natural Heavy in body, sweet, smooth, complex, fruitier
Pulped Natural More consistent with similar flavors of Dry/Natural processing

Cupping: An Observation of Taste


“Open Coffee Cupping” at the Nolita Mart on Mott Street (Jazz Guy)

Cupping is a method of evaluating coffee. Just like wine tasting, cupping is used to assess the quality of a coffee. It examines its aromas, tastes, body, sweetness, acidity, and overall flavor. It involves sniffing, sipping and slurping. The coffee is profiled with notes and characteristic taste descriptors such as “cedar,” blackberry,” and “dark chocolate.” It is used to help roasters pick and choose samples of coffee and determine the roasting level for a variety. Cupping can also help a roaster or barista describe a coffee. Using its specific language, they can also build a story for a coffee variety so customers can understand what kind
of cup of coffee they’re getting into (

Brewing Coffee: Everything is a Variable

There are a million and one ways to brew coffee. That’s a rough, exaggerated estimation but I really wouldn’t be surprised if some one actually came up with that many number of ways to brew coffee. Much like the way wet/dry processing affects the flavor of coffee, the method of brewing coffee affects the way–and how much–flavor is extracted from the beans. The method of extraction essentially depends on the type of coffee. The ground type, water temperature, and filter all depend on what type of coffee you are using and what kind of cup you want to get out of your coffee. I can exhaust myself explaining each method but I will limit myself to the parameters that affect coffee extraction.


Cafe de L’Ambre – Tokyo-5509 (Spanish Hipster)

The best way to measure your coffee is using a scale. A metric scale is the most widely used to achieve a more accurate extraction due to the fact that the density of water is almost exactly 1 g/cm3 which makes it easy to measure water when brewing coffee. Coffee is brewed in a ratio, often in a ratio of 10 to 1. So when brewing a 12 ounce cup of coffee, a ratio of 350 mL of water to 35g of coffee would be used. However, this ratio can be adjusted to preference and according to roast type.

The moment water touches the coffee granules, the coffee begins to “bloom.” In this phase, the water is first being absorbed by the coffee. The bloom time varies on the size of your coffee granules and takes longer to initially extract and absorb. After the initial blooming, the water will flow much faster and extract at a faster rate. You will immediately see the carbon dioxide trapped inside the coffee release and the coffee begins to degas and at this point, a foam or mushroom cloud will begin to form. This easily visible when you use a pour over method to brew your coffee. After the initial bloom, the water will be absorbed much faster and filter out at a faster rate.

Below is a table of all the variables that should be controlled and the consequence of over or under-doing each.

Parameters that Affect Coffee Extraction and Flavor (6, 7)

Parameter Over Under
Water Too Hot: Over-extracted coffee that has lost its quality Too Cold: Under-extracted, flat flavor
Grind Too Fine: Over-extracted and bitter Too Coarse: Under-extracted and flat
Time Too Long: Over-extracted Too Short: Under-extracted
(Depends on grind type)
Too Fine: Extraction will take a long time Too Coarse: Extraction will occur too fast and coffee extraction will not occur

The moment coffee is brewed, it should be consumed immediately. After extraction, the coffee will become stale and lose its flavor and depth. A newer technique is called cold brewing which does not use heat as a form of extraction. Cold brew requires soaking ground coffee in water for 10-12 hours or more to fully extract the coffee. In doing so, the acidity is lowered and has a stronger concentration. Many prefer this method to using hot water when making iced coffee.

It maybe over complicated but understanding coffee can be very satisfying. There is a world of science that examine recreation rates, brew times, and absorption that you can find anywhere on the internet. I encourage anyone interested to go ahead and learn more because it really is a complex and rewarding subject especially when you get your ideal perfect cup of coffee at the end.

Single Origin Coffee

The flavor of coffee is affected by its delicate growing conditions and therefore the regions where a specific coffee is grown comes with its own set of distinctive flavor profiles. This is why “single-origin” coffees are so highly prized. Single-origin means a specific coffee is grown and sourced from a specific geographic origin. Sometimes this may be defined as the general region or from a specific farm from which the coffee was produced. The term “single-origin” is still loosely defined and not thoroughly regulated.8 However, coffee connoisseurs direct more emphasis on single-origin coffees rather than blends for many reasons. The process to create single origin coffees is labor-intensive and requires the sorting of beans after harvest and separation of tree varietals. It can be time consuming, however, the results of this stringent process produce a consistent cup of coffee with clear and vibrant notes.

The Gripe of Dark Roasted Blends (Or, Why Starbucks Sucks)

I may be striking a few nerves when I say this but it’s something that *I feel many are not aware of when they consume coffee. There is a reason why so many people have ill-willed feelings towards Starbucks. You may hate its marketing tactics or its temptatious latte/frappucino drinks that masquerade as a specialty beverage, but it really just comes down to the coffee. The quality of the coffee.

Good coffee is not supposed to come cheap. Coffee farming is expensive and requires intense manual labor. However, to achieve a certain profit margin and keep the quality of coffees consistent, what many roasters do (and it’s not just Starbucks) is take a blend of cheap coffees and mix them together and roast them until they’re dark and essentially flavorless. By roasting the blends until they are dark, it masks the uneven flavors and make them more robust, heavy and seemingly complex when, in reality, they are not.


Costa Rica harvest (oddlycorrect)

Many will scoff at this and say “What’s the point? As long as I get my daily caffeine boost, I don’t care!” Though that may be the only thing what we all want from coffee, selling and purchasing coffee at such low prices actually depreciates the value of the coffee. We are living in the 21st century where just a short 150 years ago slaves were freed in 1862 and child labor was outlawed in 1938–only 77 years ago. Still today labor laws are almost nonexistent in many countries around the world. After oil, coffee is the most traded crop in the world with the source of coffee being grown mainly in developing countries.

The most expensive coffees being grown are in Hawaii, where labor laws are in place that protect the cherry pickers and also provide them a reasonable wage. Many say that the grown in Hawaii is overpriced but many others would argue that coffee everywhere else is undervalued. The price of cheap coffee is often not directly felt. It can be felt miles and miles away, in steep mountains, on small farms where laborers are working long days with little pay.


Kenyan coffee sorters (Kalle Freese)

Starbucks now offers a line of “Reserve” coffees that source coffees from rare, small lots–which I applaud (9 It’s a step in the right direction and one that I hope the public embraces. Many specialty cafes are embracing the new coffee trend of single-origins, and are now doing cuppings, and self-roastings. Understanding your craft from start to finish is critical. Just as much as we, consumers, should understand our coffee, from it origins to its processing all the way down to its brewing. It really just makes a better cup of coffee taste even better.


1: Goldschein, E. (2011). 11 Facts About the Global Coffee Industry. Business Insider. Retrieved from http://www.businessinsider.com/facts-about-the-coffee-industry-2011-11?op=1

2: Freeman, J., Freeman, C., & Duggan, T. (2012). The Blue Bottle Craft of Coffee. New York, NY: Ten Speed Press.

3: Moldvaer, A.(2014). Coffee Obsession. New York, NY: DK Publishing.

4: Kummer, C. (2003). The Joy of Coffee: The Essential Guide to Buying, Brewing, and Enjoying. New York, NY: Houghton Mifflin Company.

5: Ball, T., Guenther, S., Labrousse, K., & Wilson, N. (1999). “Roasting Coffee.” Retrieved from https://web.archive.org/web/20060912012850/http://www.wsu.edu/~gmhyde/433_web_pages/coffee/student-pages/6roasting/roasting.htm

6: Coffee Research.org. Flavor Characteristics Due to Coffee Processing. Retrieved from http://www.coffeeresearch.org/agriculture/flavor.htm

7: National Coffee Association. How to Brew Coffee. Retrieved from http://www.ncausa.org/About-Coffee/How-to-Brew-Coffee

8: Chef Jay. (2015, August 22). Eight Brewing Parameters you should Tweak to Make that Cup of Coffee Even More Delicious. Message posted to http://www.chefjayskitchen.com/2015/08/eight-brewing-parameters-you-should-tweak-for-delicious-cup-coffee.html

9: Lennart, S. (2009). Protecting ‘Single-Origin Coffee’ within the Global Coffee Market: The Role of Geographical Indications and Trademarks. The Estey Centre Journal of International Law and Trade Policy. 149-185. Retrieved from http://ageconsearch.umn.edu/bitstream/48799/2/schussler10-1.pdf

10: Starbucks Reserve Coffee. http://store.starbucks.com/coffee/starbucks-reserve-coffee/?nofilter=false

11: Information on the effects of coffee roasting: http://cyberiancafe.com/roast

12: A not-short course on coffee, with more explanation on current research in flavor compounds in coffee: Complexity of Coffee Flavor: A compositional and sensory perspective. (2014).  Retrieved from http://www.sciencedirect.com/science/article/pii/S0963996914001409


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