Screening of coffee beans Coffee bean grade

1. Grading

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 oval in shape and giant coffee beans with large grains (that is, Marragol peel coffee beans), both of which are always more expensive.

Generally speaking, the quality of large coffee beans is better. The size rating of coffee beans is usually expressed in terms of 10mur20, 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 must be removed.

The best way to separate unwanted coffee beans from good ones is to use gravity and air. The compressed air method is manual and requires higher technology, which uses jets to separate heavy and light coffee beans.

Another method is to use a weight separator to make heavy coffee beans fall by putting coffee beans on raised plates and letting air pass through them. This is also a technologically demanding method, if used properly, coffee beans can be separated more accurately and effectively.

2. Classification

After grading, these coffee beans are classified. Remove rotten, black, sour and overfermented or unshelled coffee beans. This process requires eyesight to check the beans on a moving leather bag and classify them.

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