The defects of green coffee

The defects of green coffee

When talking about green coffee, it is essential to take into consideration its quality and the defects that can influence it . However, the concept of "quality" is often used improperly, without a real correlation with the objective characteristics of the coffee itself. It is important to distinguish between the subjective taste and the objective quality of the coffee. While tastes may vary from person to person, the quality of the coffee should meet well-defined parameters established by industry experts at an international level.

The coffee market is regulated by various international organizations and bodies:

  • The International Coffee Organization (ICO) plays a crucial role in promoting fair and sustainable coffee trade globally.
  • The Specialty Coffee Association (SCA) focuses on promoting specialty coffee excellence and establishing quality standards for the industry.
  • The Common Body for Controls in the Coffee Sector (ECF) collaborates with producers and companies to guarantee the quality of coffee and compliance with international standards.
  • The European Standard Contract for Coffee (ESCC) regulates coffee trade within the European Union.
  • The stock exchanges in New York and London are important trading centers where the prices of green coffee are established.

These bodies play an important role in monitoring and regulating the coffee market, establishing standards and procedures to guarantee a certain quality of the coffee beans that are marketed.

The quality of green coffee is not a marketing parameter, which means that even if a coffee is of poor quality and full of defects, it can still be sold. Unfortunately, this means that not all coffee on the market is of high quality, but there are methods to classify defects and assign a value to coffee based on those defects.

The classification of green coffee defects is based on a evaluation table, such as that of New York (Arabica) or London (Robusta), which list the defects and their severity.
For example, the New York table, used for Arabica coffee beans, ranges from NY2 for coffees with fewer defects to NY8 for those with more defects.
Similarly, the London table is used to classify the defects of Robusta coffee beans.
The Specialty Coffee Association (SCA) also identifies several defects in green coffee beans. Some of these defects include green or unripe kernels, black or rotten kernels, kernels with shells or malformed grains, and kernels infested with insects.

These defects can affect the flavor, aroma and texture of the final drink. These rating tables help standardize the defect classification and evaluation process, providing a common basis for industry operators.

The classification of defects is carried out by taking a representative sample of raw coffee and analyzing each bean individually. The defective beans are separated and grouped according to the type of defect. Next, the total number of defects is counted and a score is assigned based on the reference table. This classification process allows to evaluate the overall quality of green coffee and determine its value on the market.

When talking about green coffee, it is essential to take into consideration its quality and the defects that can affect it.
The defects of green coffee beans can be divided into two main categories: defects primary and secondary defects. Understanding this distinction is essential to evaluating the overall quality of green coffee.

1. primary defects are considered the most serious defects and significantly affect the quality of the coffee. These defects can compromise the flavor, aroma and appearance of the roasted and extracted coffee. Some examples of primary defects include:

  • Moldy grains: these are grains infested with mold and yellowish spores due to excessive fermentation, too slow drying or storage in humid environments. These beans will bring hints of mold and stincker into the cup.
  • Black grains: The grains are rotten due to late harvesting, lack of water during fruit ripening, or excessive fermentation during the manufacturing process. In the cup, these beans will bring bitterness, harshness and hints of ash and fermentation.
  • Grains infested by insects: these are grains perforated or damaged by insects, such as the "Broca", which lays its eggs inside the drupe, i.e. the cherry that contains the grains. Other insects can attack the grains during storage under inadequate storage conditions. These beans will offer a bitter aftertaste and intense hints of tar in the cup, accompanied by a decrease in the overall aroma.
  • Brown grains: the silvery film surrounding the grain is totally over-fermented due to delays in processing, excessive fermentation or use of dirty water. In the cup, these beans will bring sourness and acetic hints.
  • Foreign bodies: such as sticks and pebbles.

2. Secondary defects are considered less serious than primary defects, but can still affect the quality of the roasted coffee. These defects can impact the flavor, aroma and texture of the drink. Some examples of minor defects include:

  • Grains in parchment: The grains are still covered in a thick, hard film called parchment, which should be removed during the depinning process. If the beans are roasted without removing the parchment, they will burn and bring a strong bitterness to the cup.
  • Dried cherries: the kernels are still inside the drupe which should be removed during the hulling process. If the beans are roasted with dried cherries, they will char and bring burning and ash aromas into the cup.
  • Grains or shells: the grains have a concave shape and/or have a large internal cavity, appearing almost "empty". These beans burn before the others in the roaster due to their thinness, bringing bitterness and hints of ash and smoke into the cup.
  • White grains: the grains have a spongy consistency due to excessive fermentation caused by bacteria or prolonged storage in humid, unventilated environments. In the cup, these beans will bring bitter and woody notes.
  • Green grains: the grains are still unripe due to early harvesting or prolonged drought. These beans do not cook during roasting like other beans, bringing bitterness, astringency and metallic flavors into the cup.
  • Broken grains: during the dehulling or depiling process, the grains break. Being smaller, they burn before other beans during roasting, bringing bitterness and hints of ash into the cup.
  • Partially brown grains: The silvery film surrounding the grain is partially over-fermented due to delays in processing, excessive fermentation, or use of dirty water. In the cup, these beans will bring sourness and acetic hints.

It is important to note that the presence of primary or secondary defects may vary depending on the growing conditions, harvesting process and green coffee processing. Therefore, careful selection of green coffee beans, free of primary defects and with a minimum number of secondary defects, is essential to obtain a tasty and high-quality drink.


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