Coffee Defects and Specialty Coffee

Specialty Coffee has very clear definitions and an evaluation system for bean qualities. It all starts at the base, the farmer and the raw material: Green beans. A lot can go wrong from seed to cup - controlling each part of the value chain of our coffee beans is of utmost importance to our final cup. Knowing your soil, plants and climate is one thing - focussed sorting out of defects is the other. Removing underripe floaters, damaged beans, insect defects, chipped or broken beans. Needless to add that foreign matters such as sticks and stones go out. Our farmers are picking and sorting by hand. Over and over again during the drying period on raised African beds.

A well organised, ideally medium sizes dry mill continues the process. Parchment, foreign matters, defects are being sorted out. Gravity is used to clean up beans and to sort screen sizes. Microlots are sorted even more by using colour readers that take multiple pictures of each bean at high speed. Lastly, very advanced dry mills used blacklight to detect potential fungus and such. The final result being very high quality green beans - the thing we are known for and control again when the beans have arrived at our roastery.

Here are the most known defects that you should never see when you are ordering a bag of beans from us:

Black Beans

Beans with 75% or more coloured surface that are often wrinkled. Some are completely black throughout whilst others can be grey-brown inside .
Cause: Cherries in contact with the ground for too long, which results in an uncontrolled fermentation. Overdue harvest which can cause a fungal infestation of the plant.
Impact on cup: Roasted bean has a grey hue and a bitter, often sour, fermented taste.

1 Black Bean = 1 Defect

Photo of black beans

Photo of full sour beans

Sour/Brown Beans

Lightweight beans with a red-brown surface, occasionally wrinkled and uneven colour. These beans can look dried out.
Cause: Fermentation of the ripe bean inside the cherry due to late harvest or lengthy contact with the ground.
Impact on cup: The beans have a lighter colour and irregular. They taste sour, bitter and astringent.

2 Sour/Brown Beans = 1 Defect

Underripe/Immature Beans

These lighter, grey-green beans are underripe and have a much lower density than ripe beans.
Impact on cup: The beans taste astringent.

5 Underripe/Immature Beans = 1 Defect


Dark green coloured beans with normal weight.
Cause: Contact with water after being pulped.
Impact on cup: Tastes musty, sour and slightly astringent.

3 Dark Green Beans = 1 Defect

Insect damaged beans can be noted by the small holes

Eroded or Corroded Beans/Insect Damage

These beans are riddled with holes. Mainly infested by Broca or Caruncho type insects. The holes have a diameter of 0,5 to 1,5mm.
Impact on cup: Small broken off fragments can carbonise and result in a bitter taste.

5 Eroded Beans = 1 Defect
2 Corroded Beans = 1 Defect


The so-called Quakers are underdeveloped and underripe beans with a light green color and a light yellow hue. At times they can have a dark brown/black color.
Impact on cup: The beans burn and taste sour, bitter and metallic.

5 Quakers = 1 Defect


Cause: Due to improper practices in the de-hulling process, leaving beans surrounded by a shell.
Impact on cup: The shell can burn or char in the roaster, possibly getting in the way of full heat contact and potentially resulting in an inconsistently roasted end product. The charred parchments taste bitter and the insufficiently roasted beans lack aroma.

2 Parchments = 1 Defect

Shells (Mussels/Ears)

Shells are deformed beans with thin outer layers that look like mussels or an ear.
Cause: Genetic and physiological factors. Especially caused by heavy rain during the flowering period.
Impact on cup: Carbonised partially or completely, they get crumbly and taste bitter and burnt.

3 Shells = 1 Defect

Photo of coffee shells from deformed beans

Chipped bean fragments cause a bitter taste to the cup

Fragmented Beans

These bean fragments are mainly caused by improper drying and/or depulping which results in thin-layered and fragments of shells.
Impact on cup: They can easily over-roast or depending on their size and the roasting degree, carbonise and result in a bitter taste.

5 Fragmented Beans = 1 Defect

Cherry Husks

Fragments of the dried cherries, mainly the result of improper de-pulping (in “natural” coffees) and insufficient screening/cleaning.
Impact on cup: They carbonise depending on their size. Can also burn and leave a bitter taste behind.

1 Big Husk = 1 Defect
2 Medium Husks = 1 Defect
3 Small Husks = 1 Defect

Photo of a cherry husk

Coffee Cherries

Improper calibration of the pulper can result in whole cherries with the beans still inside finding their way into the raw coffee.
Impact on cup: The cherries will carbonise, the beans will not roast properly, resulting in a burnt and unclean taste.

1 Coffee Cherry = 1 Defect


Different forms and sizes of stones, even at times volcanic end up in the coffee mostly through improper and insufficient de-stoning and screening.
Impact on cup: The stones rarely affect the roasting process and resulting taste, but they can seriously damage the grinder.

Small Stone = 1 Defect
Medium Stone = 2 Defects
Large Stone = 5 Defects






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