Grading and classification of coffee beans

Coffee beans are graded first by size and then by density. With two exceptions, all coffee beans have a considerable size and the same proportion, with flat on one side and semi-oval on the other. The special cases are pea-shaped coffee beans that tend to be more oval in shape and giant coffee beans with large particles (that is, Marragol peel coffee beans). The prices of these two kinds of coffee beans are always higher.

Generally speaking, large coffee beans can produce better coffee. Coffee beans are usually graded on a scale of 10 to 20, but in some countries coffee beans are graded according to levels corresponding to a certain size, such as AA. The way to determine the size of coffee beans is to pass them through a sieve. But even so, there may be weight differences between coffee beans of the same size: and bad, crumpled coffee beans that have to be removed will still remain.

The best way to separate unwanted coffee beans from good ones is to use gravity and air. The compressed air method is operated manually and requires higher technology. it uses jets to separate heavy and light coffee beans. Another method, the weight separation separator, is to put the coffee beans on a raised plate and let the air pass through them to make the heavy coffee beans fall. This is also a technologically demanding method, if used properly, the coffee beans can be separated more accurately and effectively.

The next step is to sort these coffee beans. Remove rotten, black, sour and overfermented or unshelled coffee beans. This process depends on eyesight, putting the beans on a moving belt to check.

Other methods include the electronic color classification (mainly used for Robbaut coffee beans) and the dichromate (bichromatic) method, which uses light detection to find bad beans. Today, however, the best test classifier is still the human eye. But there is no doubt that high-tech microprocessing systems will eventually completely replace this process.

Coffee beans are graded in different countries according to different grading systems. Some of them, such as those commonly used in Haiti, are overly complex and ineffective, while the sorting devices used in Brazil, despite their complex structure, are indeed necessary. Overall, there are six export grades, the highest of which is SHB (strictly hardbean), or Highland Coffee beans, which are produced in highlands no less than 400m above sea level.

All coffee beans must be evaluated before they are purchased. The usual practice is to buy coffee beans for self-baking instead of roasting coffee beans that have already been roasted in the place of production. The main reason is that once the coffee beans are roasted, their shelf life will be short. The second reason is that most retailers in America and Europe like to buy coffee beans directly from local roasters so that they can better control the quality of their coffee.