Each coffee fruit has multiple layers: the outer skin (pulp) or exocarp; the mucilage or mesocarp, a soft, sticky layer that contributes significantly to the sweetness of the coffee; a papery layer or endocarp known as parchment; and the silver skin, a membrane that encases the two seeds.
There are three methods of coffee processing commonly used today, dry processing, wet processing, and honey processing.
- Washed Processed Coffee
- Natural/Dry Processed Coffee
- Honey/Pulped Natural Coffee
Grading by bean size is increasingly used, that is, after drying, it will be measured by perforated metal plates of various sizes, ranging from 8 to 20/64 inches. For example, sieve 18 indicates 18/64 inches, while sieve 16 is 6.3mm when measured in mm. The beans that remain on the 18/64 inch sieve after placing a handful of coffee beans on it are known as sieve 18, whereas the beans that fall through and land on the 16/64 inch sieve are known as sieve 16. Due to the high density, some particles are small but cannot fall. As a result, the Specialty Coffee Association permits a 5% deviation from sieve measurements, that is, in 100 beans on sieve 18, there are allowed five smaller or larger beans.