Coffee is a brewed beverage made from the roasted seeds, or “beans,” of the coffee plant. The coffee plant is a shrub native to subtropical regions of Africa and Asia, although the plant is now cultivated throughout Central and South America as well.
Once the berries of the coffee plant are harvested, the flesh is removed and discarded, leaving only the seed. Prior to roasting the beans have a grey-green color and are referred to as green coffee; because the beans are shelf-stable at this point, they are sold and shipped green.
Coffee Bean Varieties and Types
Coffee beans vary in their size, shape, color, and flavor depending on the region and conditions in which they were grown. The range of unique flavors and aromas between regional varietals is as expansive as the variety of wine available from different vineyards. It is well worth experimenting with different varietals to discover a bean perfect for your palate.
Most regional varietals will fall into two main categories, Robusta or Arabica.
- Arabica: Arabica coffee is considered superior to Robusta because of its delicate flavor and low acidity. This variety is grown at higher altitudes and can be more difficult and costly to grow. These labor-intensive, low-yield plants produce a high-demand bean that sells for a higher price.
- Robusta: Robusta coffee tends to have a more acidic and harsh flavor than Arabica as well as higher levels of caffeine. Robusta can be grown at lower altitudes, in hotter climates, and with less moisture. Since Robusta has fewer growing restrictions and has a generally less desirable flavor, it is usually sold for a lower price than Arabica beans. Most mass-market commercial beans are of the Robusta variety.
To prepare the green coffee bean for brewing, it must first be roasted. Coffee beans are roasted with dry heat and with constant agitation to ensure even heating. The range of roasts varies from light golden brown all the way to a dark, almost black appearance. Varying the roasting time has a significant effect on the flavor, aroma, and color of the brewed coffee. Although there are several levels of roasting, they can be grouped into three main categories: light, medium, and dark.
- Light: Light roasts provide the lightest, most delicate flavors and can often be more acidic. Because there is less of a roasted flavor, the original flavor of the bean is allowed to shine through. High-quality beans or varietals with very distinct flavors are often roasted light to allow the original flavor to remain prominent. These beans will appear dry, as the bean has not been heated to the point where the oil is extracted. Light roasts include: Cinnamon, American, Half-City, and New England Roasts.
- Medium: Medium-roasted beans will have a chocolate brown color, dry surface, and a full flavor. These beans will have less acidity than lightly roasted beans and a slightly sweet, toasty flavor. Due to the balanced flavor and acidity, this is the most popular roast within the major commercial coffee market. Medium roasts are also known as Full City, Breakfast, or Regular Roast.
- Dark: Dark-roasted coffee is roasted until the sugars begin to caramelize and the oils begin to rise to the surface of the bean. Depending on the darkness of the roast, the bean may have a slight sheen or an oily appearance. The flavor of dark-roasted beans is strong, smoky, and sometimes spicy. The original flavor of the bean is overpowered by the roasted flavor and therefore lower quality beans are often used for darker roasts. Although these roasts have low acidity, they are often described as bitter. Roasts that fall within the dark category include French, Viennese, Italian, and Espresso.
- Blends: To achieve unique flavor profiles, many roasters will create custom blends of beans with two or more roasting levels. This provides a depth of flavor and complexity that cannot be achieved with a single roast.
Caffeine and Decaffeination
Coffee is perhaps most prized for its caffeine content. The caffeine content in a cup of coffee varies widely depending on the type of bean used and the brewing method. While most of the caffeine is removed during the decaffeination process, trace amounts may still remain. The international standard for decaffeination requires that 97% of the caffeine be removed from decaffeinated coffee while the European Union’s standards require no less than 99.9% to be removed.
Most methods of decaffeination follow the same basic principle: the beans are soaked in water, which allows the caffeine (and other chemicals responsible for flavor) to leach out of the beans. The extracted liquid is then either passed through a filter or mixed with a solvent to remove only the caffeine and leave the other beneficial compounds. The flavor-rich, caffeine deficient solution is then re-introduced to the beans to allow the flavor to be reabsorbed.
The Swiss Water Method has gained popularity in recent years because it uses only water to remove caffeine but the process is long and laborious. Other solvents used in the decaffeinating process include carbon dioxide, ethyl acetate, or triglycerides. Each method has its own advantages and disadvantages including cost, time, labor, and effect on the final flavor.
Research is being conducted to produce coffee plants that are deficient in the caffeine synthase gene and therefore do not produce caffeine. This would eliminate the need for the decaffeination process and would not only reduce costs but it would also keep the original flavor of the bean completely intact.
Proper storage of coffee has a great impact on the flavor of the brewed cup. Enemies to coffee’s flavor include heat, oxygen, light, and moisture. Most commercial coffee today is sold in vacuum-sealed bags with one-way valves to allow gasses to escape while keeping oxygen out. Once the seal on the bag is broken, extra care must be taken to keep the beans fresh.
At home, coffee beans should be stored in an airtight container in a cool, dark, and dry place. Although some people advocate keeping coffee beans in either the refrigerator or freezer, this can present issues with exposure to circulating air, excess humidity, and absorption of rogue flavors.
After roasting or once the seal is broken on a vacuum-sealed bag, it is best to use the beans within two weeks. For this reason, buy only the quantity of coffee that will be used within two weeks to maintain freshness and flavor.