The world of coffee beans is far more complex than that amber hue in your cup. From the small white jasmine-like flowers on the branch to the green raw beans in the processing plant, every coffee bean has undergone layers of screening by climate, altitude, variety, and processing method. There are about sixty coffee-producing countries worldwide, each grading beans according to whether they are washed or not, bean shape (flat or round), bean size, cultivation altitude, defect rate, and even taste tests. The two major varieties, Arabica and Robusta, each dominate in yield and flavor, while new crop, past crop, and old crop beans each have their own temperaments. Understanding these specifications and grading standards not only helps enthusiasts decode the terminology on packaging but also explains why beans from the same origin can present such a diversity of flavors. This article starts from basic knowledge and systematically sorts out the grading logic and processing flow of coffee beans.

Dark brown, small and round coffee beans quietly release a captivating aroma in the grinder, and after brewing, they reveal an amber-like luster in the cup—these three images are probably the most vivid impressions most people have of coffee.

Unfold the long scroll of coffee history, and you will also see coffee trees swaying their green leaves under the tropical sun. The white flowers they produce resemble jasmine somewhat, and the fruit gradually turns from green to yellow-green, finally taking on a ripe red color, with the coffee bean hidden inside the fruit as its seed.

If you walk into a coffee bean processing plant, you will see the red pulp known as "coffee cherry," as well as fresh raw beans that have already had their parchment and silver skin removed, revealing a verdant color—these are the coffee beans used for export.

Currently, about sixty countries worldwide produce coffee, with most growing areas located between 300 and 400 meters above sea level, though there are also cases of cultivation at high altitudes of 2000 to 2500 meters. Generally speaking, however, coffee beans produced on hillsides above 1500 meters are considered to be of better quality.

The ideal growing environment for coffee trees is: average annual rainfall of 1500 to 2000 millimeters, average temperature of around 20 degrees Celsius, and areas free from frost damage.

Coffee belongs to the Rubiaceae family of evergreen plants and can grow to over eight meters in the wild. On farms, however, to ensure bean quality and facilitate management, trees are usually pruned to about two meters in height.

There are currently three main original species under cultivation: Arabica, Robusta (also known as Canephora), and Liberica. These original species can be further divided into dozens of varieties, which are distinguished in production, distribution, and trading.

Even within the same country, differences in climate, altitude, and soil conditions across regions can subtly affect the flavor and quality of coffee beans, giving each its own unique character. Therefore, it is difficult to summarize the characteristics of a country's coffee beans based solely on variety, origin, or brand.

Specifications and Grades of Coffee Beans

A. Washed and Unwashed

Washed: The fruit is placed in a water tank, where water flow and mechanical friction remove the pulp and mucilage, followed by drying, resulting in coffee beans of uniform and consistent quality.

Unwashed: After natural drying in the sun, the pulp and skin are removed with a huller, resulting in relatively inconsistent quality.

B. Flat Beans and Round Beans

Coffee fruit usually consists of two oval seeds growing facing each other, with the side where they meet being flat, known as flat beans. There are also cases where the fruit contains only a single round seed, known as round beans, which have no difference in flavor. The ripe, red coffee cherry has a multi-layered structure, with the pale green seed—the predecessor of the coffee bean—at its very center.

In summary, coffee fruit mostly consists of two oval seeds facing each other with a flat connecting surface, hence called flat beans; there are also round beans formed by a single round seed, with no difference in taste.

C. Size of Coffee Beans

The correspondence between mesh number and coffee bean size is as follows:

Flat beans: 20~19 is extra large, 18 is large, 17 is quasi-large, 16 is standard, 15 is medium, 14 is small, 13~12 is extra small.

Round beans: 13~12 is large, 11 is quasi-large, 10 is standard, 9 is medium, 8 is small.

D. Altitude

According to the altitude of the cultivation site, beans can be classified into different grades such as 3, 4, or 7. Overall, highland beans are superior to lowland beans, and due to increased shipping costs, their prices are relatively higher.

Correspondence between grade, name, and altitude (meters): Grade 1, Special Grade, above 1500 meters; Grade 2, Premium Grade, 1200~1500 meters; Grade 3, Medium Grade, 1000~1200 meters; Grade 4, Special Washed, 900~1000 meters; Grade 5, Premium Washed, 760~900 meters; Grade 6, Extra Fine Washed, 610~760 meters; Grade 7, Fine Washed, below 610 meters.

E. Quality

Through statistical methods, the types and quantities of impurities in a certain amount of sample are converted into a percentage, known as the "defect count," which serves as the basis for quality classification. The smaller the defect count, the higher the quality.

F. Taste

Countries such as Brazil, Haiti, Kenya, and El Salvador each have their own independent taste testing methods, and only coffee beans that pass the taste test are permitted for export.

Arabica and Robusta

Arabica accounts for about two-thirds of global coffee production. It is not suited to high temperatures, low temperatures, excessive rain, or drought. Its beans are oval with flat shoulders, characterized by rich aroma and superior quality.

Robusta has a pronounced bitterness without acidity, and its aroma is not particularly outstanding, making it suitable for blended coffee. Blending an appropriate amount of Robusta with Arabica is commonly used for making iced coffee, instant coffee, and canned coffee. This variety grows in lowlands and has strong disease resistance.

Liberica's quality and yield are both unsatisfactory, and most of it is exported to Europe, never entering the Japanese market.

New crop beans are pale green in color, with a unique acidity and coffee aroma, showing a distinctive character. (Right)

Past crop beans are slightly yellow with a hint of pale green, and their acidity is milder than new crop beans. (Middle)

Old crop beans turn yellow after moisture loss, with weak acidity and ordinary taste, usually used for blends or canned coffee. (Left)

From Harvest to Shipment

After the fruit is harvested and before it is shipped to market, the outer skin, pulp, parchment, and silver skin must be removed. The methods are divided into the dry method (also called the natural method or unwashed method) and the washed method. The dry method is relatively simple to carry out.

Specifically, freshly picked fruit is spread flat on a drying yard for one to two weeks until the fruit makes a crackling sound, completing natural drying. Then a huller is used to remove the shriveled pulp, parchment, and silver skin. Coffee beans processed this way are slightly acidic with a hint of bitterness. Almost all coffee beans from Brazil, as well as those from Ethiopia, Yemen, and other places, use this method. Its drawbacks are that it is easily affected by weather and prone to mixing in defective beans and impurities, so careful screening is essential.

The other method is the washed method: harvested fruit is placed in a flowing water tank, and after removing the fruit floating on the surface, the outer skin and pulp are stripped off with a pulping machine. Then they are placed in a water tank to remove the floating pulp. After that, they are moved to a fermentation tank and soaked for half a day to a day to dissolve the mucilage on the surface of the fermented coffee beans. After washing and sun-drying for several days, they are machine-dried, and finally the parchment is removed with a huller, resulting in raw coffee beans ready for sale as a commodity.

Washed coffee beans have a more beautiful color and fewer impurities. About 70% of the production from Colombia, Mexico, Guatemala, and other countries uses this method. If the fermentation process is not handled properly, it may produce a fermented odor and a distinctive acidity; but if handled well, each type of bean can give off its own unique coffee aroma. To arrive safely at its destination, raw coffee beans are packed into burlap sacks, placed in special containers, and embark on a long voyage by merchant ship.

(This article is reproduced.)

The above content is compiled by CoffeeHunters, a coffee news website.