Poor beans. They’ve been picked, washed, stripped, dried, and now they will be classified. Even after the wet classification process—where bug-eaten and unripe beans are separated from red cherries—there are still ways to make coffee better. This is the dry classification process.
In late November, after the pulped beans have dried and rested, we run them through another series of machines. It’s kind of like an amusement park for coffee beans—lots of drops, turns, and spins. Only when beans leave this ride, they are transformed. We are essentially creating a series of gates to make sure bad beans—bug-eaten, sour, unripe, malformed, broken—do not get into the final product.
The first machine uses sharp sieves to hull beans. After pulping, coffee beans are covered by a stiff husk that, after drying, has the texture of a fingernail. This husk must be removed before beans are roasted. Underneath the yellow husk is the raw coffee bean most of us are familiar with: sage-green in color, rounded on one side and flat on another, with a line through the middle.
After hulling, beans are dropped into a second machine that uses another set of sieves that sort by size. Size 10’s, also known as “peaberries,” are the smallest beans. Size 18’s are the largest. (A quick note: the peaberry is an anomaly of nature. When two bean halves fuse inside the cherry, making an oval-shaped bean, this is a peaberry. Peaberries are considered to have amazing flavor because their oval shape makes them roast better.) Why are beans sorted by size? It’s all about the roasting process, which is essentially cooking beans. Small things tend to cook faster than large things. The same is true with coffee—if small beans and large beans are roasted together, the smaller beans will burn to a crisp while the large beans might be perfectly roasted. This adversely affects the flavor of roasted coffee.
After beans are sorted by size, each lot (Size 10, 14, 15, 16, 17, 18) is run separately through our density table. Have you ever played air hockey? Well, the density table is essentially a large air hockey table, only angled to one side. Bad beans that snuck their way through all other gates will not usually get through this one. Bug-eaten, broken, sour, and malformed beans generally weigh less than good beans. Air lifts these bad beans higher, while better beans stay low. So good beans float to the special exit, while bad ones go into the reject pile.
Specialty grade coffee has no more than 5 full defects in a 300 gram sample. No primary defects (sticks, stones, husks) are allowed. Why such rigid standards? It’s all about the roast. Coffee beans must be roasted before they’re consumed, and roasting is a science all its own. Roasting will be the final and sixth part of The Life of a Coffee Bean.
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