Continuing with our Green Bean Series, this month we’re going to take on defects in wet processed Arabica coffee beans; their cause, how to identify them and the effect they have on the roast.

Our “Roasters Tools – Green Bean Series” is a five part evaluation of how the characteristics of green coffee beans affect the outcome of the roast.

Roasters who consistently purchase strictly top grade premium coffees may have only rarely been confronted with defects, while the majority of roasters run across them much too often, even when presented with what is being sold as “Specialty” grade coffees.

The fact is, any one of these dozen defects will negatively affect the quality and alter the taste of the coffee you’re producing. These defects are both identifiable and preventable.

The defects in this article are different than the “formation” defects we talked about in a previous article.

With that in mind, we aim to give you a very straightforward, to the point identification of what these defects look like, their causes, and how they can affect the profile of your roast.

The Twelve Key Defects To Look Out For:

  1. Faded Beans
  2. Amber Beans
  3. Coated Beans
  4. Green Water Damaged
  5. Pulper Damaged
  6. Insect Damaged
  7. Immature Beans
  8. Foxy Beans
  9. Triple Center Cuts
  10. Stinkers
  11. Over-Fermented
  12. Diseased


Faded beans can be a result of either over drying or absorbing excessive moisture, depending on the environment. Either way, faded beans have a low resistance to environmental factors.

The effect on the roast is that they give a dull roast regardless of the roasting profile. The result is a soft bean with musty and woody flavors in the cup. And, the percentage moisture loss will be very high. The color of these beans is pale, whitish brown.

Normally, they result from beans that have a high moisture content (11% – 13%) and when stored in a warehouse, they’ll tend to dry out. In the process of drying out, and because they are not in contact with direct sunshine, these beans tend to fade.

Instead of drying, these beans are actually rotting and developing molds inside. It’s these molds that cause the beans to dry excessively, producing their pale to whitish brown color.

In addition, during the drying of wet or dry processed beans, the coffee can be negatively affected if not properly exposed to sunshine at the appropriate stage in the drying process.

Another cause is when coffee has been over-hulled using a hammer mill. In this case, the beans will come out with a dull color as a result of the outer cells being bruised and microscopic dust permeating the outer layer of the beans.

One final factor that can contribute to the fading of coffee beans is from older coffee that has been kept in a warehouse for two to three years or more, causing the beans to dry out, develop molds and other negative consequences.


These beans have a bright shiny gold color. The cause is due to mineral deficiencies in the soil (including iron).

When you roast these beans, the cup will be lacking in acidity, with a flat harsh body and a bitter flavor. Also, the roast produced by these beans will be very dull in color.


These beans have a sticky silver skin caused by either overbearing or from being drought affected. The characteristics of these beans look whitish, rough and display microscopic lines from the silver skin.

In the process of roasting, you’ll experience soft beans with excessive chaff. The roast can result in negative effects in the cup, including excessively high grassy, hay, earthy, woody, greenish and potato flavors.

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