Coffee Buying Overview
The green coffee seller is responsible for grading a coffee before sending the coffee to the buyer. Once graded, “Exceptional” and “Specialty” coffees can still have problems that are not necessarily account for in coffee grading. These “defects” are less serious, but harm the potential of the coffee. You can tell a great deal about the processing conditions of a coffee by looking at the appearance of the green coffee. Although cupping is the definitive way to check for problems, the green coffee appearance is a good prognostic tool.
- The green beans should be of nearly equal size 17/18, 15/16, 13/14 etc, be similarly shaped, and have a similar color. The reason for this has to do with how evenly the coffee will roast which will affect the appearance and taste of the roasted coffee. Smaller beans will roast differently than larger beans resulting in an uneven cup. Uneven coloring hints toward drying problems, whereas uneven shapes may indicate a mixing of cultivars.
- Ensure that the producer separates lots by both geographic area and cultivar. These lots should be harvested, processed and cupped separately before blending in the silos.
- Washed Arabica coffees should be even and bright. The beans should not have an uneven or dull color. If they do, it is likely they have been dried or processed incorrectly. If the green beans look faded, the cup quality will be faded.
- Inquire about the coffee drying conditions on an estate. If they seem to have invested a significant amount of time into ensuring that they are drying the coffee properly considering the climatic conditions the coffees will generally show this in the cup. Improper drying on patios or in mechanical dryers can usually be observed visually. Rapid drying in mechanical dryers results in dull or brown coffees. Beans that are mottled (or quakers when roasted) result when the coffee is dried too quickly, spread too thin on the patios, or not rotated as frequently as recommended. Some people recommend drying on patios first to dry the skin, then transfer to mechanical dryers, and then bring the coffee back to the patios for the final drying. They believe that this helps improve color. Others send a coffee to the dryers several times while in between drying sessions they allow the coffees to rest in silos so that the moisture content of the bean can come to equilibrium. This is important since the outside of the bean will dry faster than the inside of the bean. Inquire about the temperature used on the dryers. Is it over 42 degrees Celsius? If so you can expect a dull or baked cup.
- For all coffees, inquire about the processing. Make sure they process the coffee immediately upon harvesting. Otherwise you are guaranteed a fermented cup since coffee begins fermenting immediately upon picking. Ask how they use the fermentation tanks and why? Do they separate out coffees that float to the top of the tanks during fermentation? After pulping do they separate coffees by density before they add them to the tanks? Only estates that have dedicated a significant amount of time to improving quality will know why these steps are important and necessary. If coffee pulp is present in the tanks during processing it can result in brownish tinges on the green beans. This is also indicative of harvesting over-ripe cherries.
- Natural (dry) processed coffees will often be covered in brown silver-skin which has attached itself to the bean. In Brazil they call this a fox bean and it is not considered a defect. Novice classifiers might expect this type of bean to be a defect, but if you can remove a portion of the silver-skin by rubbing on the black sorting mat it is not considered a defect. Green (under ripe) coffee also has a silver-skin attached to it, but this cannot be removed by simple rubbing. In a washed coffee, fox beans may indicate sour, fruity, or Rio tastes. This should be confirmed in the cup and not visually.
- Do the beans have a little pink skin covering them or inside the crack of the bean? In some area this is a serious defect which most people do not consider to be a defect. Since it is not part of the green coffee classification, these beans could be passed on to the buyer as specialty grade. These beans should be separated and cupped to determine if the defect is serious.
- Are the beans whitish or faded around the edges? This is likely a result of insufficient drying or storage in humid conditions. The cup will be bland and ordinary. These white marks are also observed in coffee that has not been dried evenly. The part of the bean that has a whitish tone has higher moisture than the other parts of the bean. Whitish or discolored beans can also result from oxidation, contact with the earth, or polluted waters.
- Smell the green beans. Ferment and smoke damage can be easily detected at this point, whereas they might be more subtle when roasted.
- Pick up the green beans. How do they feel? If they feel glass-like and fragile they have been over dried or dried at too high a temperature. If they are pliable they have not been dried sufficiently and should be rejected since mold growth at this point is unavoidable.