Defect green beans are beans where something on the farm, in the processing plant, or during transport influenced the bean in a negative way, which will most likely result in an off flavor, or can even have a negative influence on your health. Non-coffee beans (foreign material) also count as a defect, as it might cause damage to your roasting equipment, and again, might pose a health issue.
As first-time graders quickly find out, you need a good pair of experienced eyes, an amazing neutral light lamp, and a dark underground, if you do not want to be green grading the same lot for an hour. Not only can it be difficult to decide if a weird looking coffee bean is defective, or just not mother nature’s most beautiful.
Some defects ‘weigh heavier’ than other defects, such as black beans which can make a cup taste fermented, dirty, moldy, sour or phenolic and has a higher risk of Ochratoxins. Slight insect damage might just influence roast consistency, and so weighs less heavy. You need either 5 or 10 insect damage beans, depending on severity, to count 1 ‘green coffee defect’.
These number of equivalents to ‘one defect’ can differ per origin. Additionally, there are many different types of grades. There are origins that work with numbered grades (one, two, three, etc), but also origins working with letters, or different preparation types (European prep vs. American prep), and so on. Many of them have different ‘equivalents to defect’.
And that is not all. Even when it looks the same on the label, it might be different. An Ethiopian grade one, allows for less defects than an Indonesian grade one. Additionally, your trader might have set their own table of equivalents, where they agreed on a certain green grading standard with their suppliers. Confused yet?
Know the preparation of your green coffee; what does the label say about the grade, and what does that mean? Although standards may differ from place to place, the Green Coffee Defect Handbook of the SCA is a very useful tool. Get a black background, get a good lamp, set a timer to avoid green coffee staring, and off you go.
You can find our Ethiopian standard within the ‘How to recognize and distinguish coffee defects’ poster. It gives an overview of what we might encounter during the green grading of incoming samples.