Let's talk about coffee quality. This is largely dependent on the quality of the green coffee beans. Good raw materials are always the starting point of the roasting process. A roaster needs a good foundation to achieve fine roasted coffee results. – Pretty much everyone would agree with that. But what happens to the "poor" quality beans?
To understand this, we first need to define what is meant by "good quality." Simply put, good green coffee quality is characterized by sufficient ripeness, proper storage, a moisture content of around 11%, homogeneity in size and density, and the absence of coffee defects with accompanying off-flavors. Homogeneous green coffee helps roasters achieve consistent roast levels. With a mix of different bean sizes and densities, smaller and less dense beans are exposed to more heat relative to their mass than denser and larger ones. This imbalance leads to inconsistencies and extremes in the cup. Furthermore, the subjectively perceived quality is defined by the aromas and flavors that develop during roasting, influenced by the region, terroir, and prevailing climate. Regarding the more general Q-criteria, in addition to the coffee farmers, the so-called "dry mills" play a significant role, whether operated by large producers themselves, cooperatives, or exporters.
What is the important role of dry mills? They sort and classify the different qualities of green coffee beans. A ripe cherry produces a coffee bean with a higher density than one with a lower degree of ripeness. Larger beans from the same field and of the same variety indicate better nutrient supply than smaller ones. Therefore, in dry mills, the dried coffee beans are freed from the parchment layer, dedusted, and have foreign matter removed. They are then sorted granulometrically (by size), densometrically (by density), and electronically by color grading.
In broad terms, this means: The beans are separated into screens 15 (small) to 18 (large) using sieving systems. Afterwards, the different sizes are sorted via "upward flow graders"—sloping, perforated sorting tables with hurdles, where compressed air is blown upwards from below.
The beans are separated into higher and lower densities. The highest-density beans remain at the top of the sloping sorting table, while the lower end usually contains the defective beans. Finally, any remaining defective beans are electronically sorted out from the separated fractions based on their visible discoloration. Therefore, when purchasing beans, a roastery differentiates not only based on the quality of a producer's agricultural practices and post-harvest processing, but also between the various quality fractions of the harvest volume. And everything except the purely defective beans is sold. Understandably, producers are interested in selling their entire harvest to make a profit. Many producers could not survive economically by selling only the best quality fractions, unless they are highly specialized. However, it is a fact that producers can earn good money with the better fractions. In summary, it must be said honestly that while it's important for all qualities of coffee to be traded on the market so that producers can sell their harvests, it's even more crucial that the very best qualities are recognized and showcased. High-quality coffees create competitive pressure and raise the overall standards in the coffee market. This is perhaps the greatest achievement of the specialty coffee movement.
Recognizing that there is still much potential in terms of quality and working together with customers to create pressure so that qualities are compared and rewarded.
Original article
"Everything must go!" | Why specialty coffee roasters and industrial roasters need each other.