How to choose defective coffee beans? There is a knack for picking coffee beans.

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Manual sorting is efficient, and the trick lies in the regularization of the sorting process.

Hand-picking out defective beans from a large number of coffee beans is a very time-consuming and labor-consuming task. But as long as you get the hang of it, you can do it efficiently.

When picking out defects in raw beans, it is recommended to spread the beans on a dull black tray. For example, the color of fermented beans or unripe beans will be slightly yellow, and it is easier to identify them with dark trays. As for the manual sorting of baked beans, in order to easily see the difference in baking color, the cooked beans are also spread out on a tray covered with brown cotton cloth to make the sorting work easier.

After spreading out the coffee beans, you can start picking out defective beans, but a disorganized operation will only waste more time. The trick to making manual sorting more efficient is to first determine the priority of the work and think about which kind of defective beans to start with. First of all, the order of inspection is "color > gloss > shape". After getting rid of the foreign bodies and black beans that are obviously different from raw beans, there are dead beans, fermented beans and unripe beans without "luster", and finally defective beans such as shell beans and worm-eaten beans with strange shapes.

With regard to the proportion of defective beans sorted by hand, about 15% of the raw beans treated by water washing and 40% of the sun-dried beans. Of course, it is ideal to buy raw beans with few defects in the first place; however, defects are inevitable, so it is necessary to estimate in advance the amount that will be reduced after deducting defective beans in order to calculate the necessary purchases. It is a pity that the coffee that takes time and energy to brew will be destroyed because of a defective bean; in order to avoid regret, it is safer to pick it out decisively if it is difficult to judge whether it is normal or defective.

Common impurities in coffee beans:

1. Stone

Coffee beans dried naturally in the sun are likely to be mixed with pebbles, gravel, wood chips and other foreign bodies. Occasionally a piece of glass or coins will be found.

2. Cereals

Like stones, coffee beans that are naturally dried in the sun may be mixed with cereals or seeds such as corn, and pepper grains have been seen.

Common defective bean patterns:

1. Shell beans, broken beans

Beans that become shell-shaped because of developmental problems are called "shell beans"; beans that are damaged during treatment or transportation are called "broken beans", both of which can cause uneven baking.

2. Fermented beans

When treated by water washing method, polluting fermented beans are produced in the fermentation tank. Delayed processing or improper preservation can also occur after harvest, and beans will smell funny when baked.

3. Moth-eaten beans

Because pests such as coffee bark beetles lay eggs on coffee trees, and the hatched larvae eat coffee fruits to form cavities, which is the reason for the turbid or strange taste of coffee.

4. Moldy beans

Beans that are moldy due to incomplete drying, transportation or improper preservation will remain moldy even after baking.

5. Unripe beans

Beans harvested before the coffee fruit is ripe. Coffee mixed with unripe beans will have a strong fishy smell, giving off a disgusting, smelly smell.

6. Black beans

Beans that fall black before harvest, or beans that are completely fermented and damaged. It is the source of the foul smell and rotten smell of coffee.

7. Dead beans

Beans that fail to bear fruit normally will lead to weak flavor and strange taste of coffee. The color after baking is also not good, so it is easier to distinguish after baking.

8. Smelly beans

The beans are dried when the pulp is attached, or the pulp is removed from the beans. Stinky beans give off the smell of iodine or soil.

9. Sheepskin membrane beans

Due to incomplete shelling and other reasons, the beans with residual endocarp are the reasons for the astringent or miscellaneous taste of coffee.

Raw beans can be identified by black trays that do not reflect light.