1. The core logic of coffee bean grading
There is no unified standard for the global coffee grading, which is mainly based on the following dimensions:
Bean size (screen aperture): such as Kenya AA (above 8.2mm)
Defect rate (number of defective beans): such as Ethiopia G1 (≤3 defects per 300g of raw beans)
Altitude: such as Central America SHB (Strictly Hard Bean, ≥1200 meters)
Density and hardness: Beans at high altitudes are denser and can withstand high temperatures when roasted
2. Detailed explanation of the grading system of mainstream production areas
（1）East African system: AA, AB, PB
Kenya AA，AB，PB
AA：Bean size: above mesh 18 (7.15mm), the highest grade (accounting for 10-15% of production)，Flavor characteristics: high acidity, black currant flavor (such as SL28/SL34 varieties)
AB : mesh 15-16 (6.8-7.15mm), cost-effective choice
PB (Peaberry): round beans (single embryo), accounting for about 5%, concentrated sweetness
（2） Ethiopia: G1-G5
G1 (Grade 1): defect rate: ≤3 beans/300g raw beans (manually screened 3 times) Representative beans: Yirgacheffe G1 washed (jasmine fragrance)
G2-G5: defect rate increases (G5 allows 46 beans/300g), mostly used for commercial blending
（3）Central America: SHB, HB
SHB (extremely hard beans): Altitude: ≥1370 meters (Costa Rica), ≥1200 meters (Guatemala) Features: slow growth, high sugar accumulation (suitable for light roasting)
HB (hard beans): 900-1200 meters, mellowness is preferred (such as Honduras HB)
（4）Other important standards
Brazil: NY2/3/4 (number of defects + cupping score)
Indonesia: G1-G6 (defect rate + bean size, Mandheling G1 is the highest)
Colombia: Supremo/Excelso (screen No. 17/No. 16 and above)
（5）atcbonnet: AA, AB, C
Grade AA: Specialty coffee beans
Grade AB: Blended coffee beans, cost-effective
Grade C: Commercial coffee beans
Is AA grade Arabica?
Yes. Robusta beans do not use AA grading (Vietnam has E and S grades).
Why is Yirgacheffe more expensive than Sidamo, both of which are G1?
Difference in processing costs (washed Yirgacheffe requires a lot of clean water, while sun-dried Sidamo is more dependent on the weather).
Can SHB beans be used for espresso?
Yes, but they need to be medium-dark roasted (such as Costa Rican SHB honey processing).
What grade of coffee beans does atcbonnet use for sale and how are they processed?
atcbonnet uses AA grade coffee beans as its top choice，the processing include washing, sun drying and honey treatment.