To ensure coffee meets its required standard for roasters, green coffee bean grading systems are integral in the coffee supply chain. The process of grading coffee involves the consideration of several different factors such as the size of the coffee beans or the amount of defects found in a sample. Consistency is key, especially for roasters that want to sell high-grade speciality coffee to their customers.
Grading systems have evolved in line with the requirements of green coffee buyers. This is especially important when considering the defects found in coffee as this can increase the risk of contamination. This means that safety considerations are also important regarding wider international recommendations on grading.
From Coffee Harvesting to Grading
A coffee grading system is a classification for picked and prepared green coffee beans. Grading is important as it determines quality and adheres to a fair system of pricing. Each producing country has its own classification and grade charts, which are often used to set minimum standards for export.
After harvesting, coffee needs to go through a few processes until it is ready for examination, grading, and eventually trading.
Harvested coffee is sent to a wet mill, also known as a “washing station” in Africa. Milling is when the coffee seed is extracted from the cherry fruit through a method called pulping. (This process is achieved through methods such as fermenting, washing, and drying). Then after the beans are pulped, fermented, washed, and dried, they are then taken to a dry mill. For natural process coffee, the harvested cherries are left to dry in the sun for some time, allowing the pulp to naturally dry up, shrink, and eventually solidify.
In the dry mill, the coffee is then hulled and sorted. During the hulling process, the beans are checked for impurities or stones before the final parchment layer is removed. It is after this process that the beans are then sorted and differentiated by size, colour, and density. Beans must be uniform since this determines the speed and consistency of a roast.
The basic premises for grading coffee
There are 10 basic properties of green coffee beans that are typically assessed when grading and classifying coffee beans. These attributes apply to coffee from all countries and are important for producers, roasters, and consumers alike.
These attributes are:
Altitude
Region
Botanical Variety
Bean size
Preparation method
Bean shape and colour
Number of defects
Permissible defects
Cup quality
Bean density
In general, roasters should be thinking of these qualities when considering the coffee they purchase from producers and suppliers. Since there are so many factors involved in grading and classifying coffee, many of the employed methods of grading are usually very diverse and complex.
The significance of bean size and density
Typically, although not always, the size of coffee beans indicates their quality. Larger beans are commonly considered to be of a much higher quality and these larger sizes are often due to high-altitude farming. Coffee grown at higher altitudes can develop at a much slower rate due to cooler temperatures. This means that the coffee cherry (which eventually becomes the coffee bean) can take more time to absorb nutrients from the soil. This results in larger and denser beans. It is this process that can provide the coffee with its much sought-after sweetness and full-bodied taste.
When grading coffee, the consistency of the weighed sample is fundamental. Without this uniformity, the coffee roast will be uneven, resulting in a ruined product. To assure consistency, coffee is sorted into sizes through the use of hole-punched screens. Bean size is expressed in 1/64 of an inch. For example, screen 18 would be a screen consisting of holes that are 18/64” in diameter. When sorting beans, they are passed through layers of screens of varying sizes.
When sorting coffee beans, screens are used. In this process, the screens are layered on top of each other, in which the coffee beans are then passed through. Each screen consists of different-sized holes measured in diameter. As the coffee passes through the screens, consistent sizes are caught. This means that the coffee is adequately sorted for cupping.
In general, the sizes span from very large, large, medium, small, and shells. Sizes are classified differently depending on different parts of the world:
Bean size (1/64 inch) | Classification | Central America and Mexico | Colombia | Africa and India |
20 | Very Large | Superior | Supremo | AA |
19.5 | ||||
19 | ||||
18.5 | Large | |||
18 | A | |||
17 | ||||
16 | Medium | Segundas | Excelso | B |
15 | ||||
14 | Small | Terceras | C | |
13 | Shells | Caracol | - | PB |
12 | ||||
11 | Caracolli | |||
10 | ||||
9 | Caracolillo | |||
8 |
After sorting coffee beans based on size, they are then ready to be weighed in sample sizes, and examined for defects, and eventually, cupping quality.
SCAA Grading System
SCAA (Specialty Coffee Association of America) is the most standard and popular method used for grading green coffee beans. It can be considered the best grading system since it accounts for the relationship between defective coffee beans and cup quality better than other systems.
When using the SCAA method, the coffee is sorted with screens that range from 14/64” to 18/64” diameter holes. Once sorted, 300g of coffee is ideally used for examination. This can be time-consuming, however, so typically, 100g is used. For high-grade coffee with only a few defects, 300g should be used. Lower-grade coffee should be fine with just 100g. When examining the coffee, defects are important to identify since they result in the final grading of the coffee. These defects are categorised as primary and secondary defects:
Primary Defects | Secondary Defects | ||
Primary Defect | Number of occurrences equal equal to one full defect | Secondary Defects | Number of occurrences equal to one full defect |
Full Black | 1 | Parchment | 2-3 |
Full Sour | 1 | Hull/Husk | 2-3 |
Pod/Cherry | 1 | Broken/Chipped | 5 |
Large Stones | 2 | Insect Damage | 2-5 |
Medium Stones | 5 | Partial Black | 2-3 |
Large Sticks | 2 | Partial Sour | 2-3 |
Medium Sticks | 5 | Floater | 5 |
Shell | 5 | ||
Small Stones | 1 | ||
Small Sticks | 1 | ||
Water Damage | 2-5 |
Specialty Grade Green Coffee (1) |
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Premium Coffee Grade (2) |
|
Exchange Coffee Grade (3) |
|
Below Standard Coffee Grade (4) |
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Off Grade Coffee (5) |
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The SCAA method of classification is popular due to its comprehensive analysis of the coffee beans. It takes a well-rounded approach to the many attributes involved in determining the quality of examined coffee.
Brazil / New York Method
Although SCAA is considered one of the best methods of coffee grading, the Brazilian method is much better equipped to consider defects. Also known as the New York Method, this system scores the coffee with a maximum of 100 points, mostly based on the amount of defects found in 300g.
Defects are split into two sections: Intrinsic Defects and Foreign Defects. This method allows for a maximum of 1% of foreign defects:
Intrinsic Defect | Number | Full Defects |
Black bean | 1 | 1 |
Sour (including stinker beans) | 1 | 1 |
Shells | 3 | 1 |
Green | 5 | 1 |
Broken | 5 | 1 |
Insect damage | 5 | 1 |
Malformed | 5 | 1 |
Foreign Defect | Number | Full Defects |
Dried cherry | 1 | 1 |
Floater | 2 | 1 |
Large rock or stick | 1 | 5 |
Medium rock or stick | 1 | 2 |
Small rock or stick | 1 | 1 |
Large skin or husk | 1 | 1 |
Medium skin or husk | 3 | 1 |
Small skin or husk | 5 | 1 |
After examining the number of defects in the weighed coffee, the sample is scored as follows:
Defects | Type | Points | Defects | Type | Points |
4 | 2 | 100 | 49 | 5-5 | -55 |
4 | 2-5 | 95 | 53 | 5-10 | -60 |
5 | 2-10 | 90 | 57 | 5-15 | -65 |
6 | 2-15 | 85 | 61 | 5-20 | -70 |
7 | 2-20 | 80 | 64 | 5-25 5/6 | -75 |
8 | 2-25 2/3 | 75 | 68 | 5-30 | -80 |
9 | 2-30 | 70 | 71 | 5-35 | -85 |
10 | 2-35 | 65 | 75 | 5-40 | -90 |
11 | 2-40 | 60 | 79 | 5-45 | -95 |
11 | 2-45 | 55 | 86 | 6 | -100 |
12 | 3 | 50 | 93 | 6-5 | -105 |
13 | 3-5 | 45 | 100 | 6-10 | -110 |
15 | 3-10 | 40 | 108 | 6-15 | -115 |
17 | 3-15 | 35 | 115 | 6-20 | -120 |
18 | 3-20 | 30 | 123 | 6-25 6/7 | -125 |
19 | 3-25 3/4 | 25 | 130 | 6-30 | -130 |
20 | 3-30 | 20 | 138 | 6-35 | -135 |
22 | 3-35 | 15 | 145 | 6-40 | -140 |
23 | 3-40 | 10 | 153 | 6-45 | -145 |
25 | 3-45 | 5 | 160 | 7 | -150 |
26 | 4 | 0 | 180 | 7-5 | -155 |
28 | 4-5 | -5 | 200 | 7-10 | -160 |
30 | 4-10 | -10 | 220 | 7-15 | -165 |
32 | 4-15 | -15 | 240 | 7-20 | -170 |
34 | 4-20 | -20 | 260 | 7-25 7/8 | -175 |
36 | 4-25 4/5 | -25 | 280 | 7-30 | -180 |
38 | 4-30 | -30 | 300 | 7-35 | -185 |
40 | 4-35 | -35 | 320 | 7-40 | -190 |
42 | 4-40 | -40 | 340 | 7-45 | -195 |
44 | 4-45 | -45 | 360 | 8 | -200 |
46 | 5 | -50 | >360 | Above 8 |
Generally, coffee without defects, while being consistent in size, colour, and shape, are considered specialty coffee via this method.
Country Specific Coffee Grades and Classifications
Both SCA and the Brazilian/New York classification systems provide a comprehensive overview of grading coffee around the globe. Since they are so generalised in their grading quotas, they are most useful for grading and classifying commercial coffee, however.
Specific and bespoke coffee grading systems are often unique to each country of origin and this is especially the case for African coffee. This allows for much more precise grading, resulting in further transparency throughout the African coffee supply chain. Many of these systems can vary in complexity and can change depending on factors such as the coffee’s processing method.
Below are some examples of the different coffee grading systems throughout African origin countries:
Ethiopia
Ethiopian coffee is typically classified with the G1-5 grading system that is dependent on the amount of defects. The grades descend from 1 which is the highest quality.
Ethiopian Coffee Grade | Defects |
1 | 0 - 3 |
2 | 4 - 12 |
3 | 13 - 25 |
4 | 25 - 45 |
5 | 46 - 100 |
6 | 101 - 153 |
Within the specialty market, Grade 5 is typically the lowest permissible, although grades are known to go as low as 7 and 8, which are considered very low quality and are not allowed for export.
The term U.S.Q (Usually Good Quality) is often used to denote grades 3, 4, and 5. Between grades 4 and 5 is ‘Grade 5 Europrep’, where the coffee should not exceed 80 defects, and is considered an improved G5.
Ethiopia’s G1-5 system provides a great introduction to how its coffee is classified for the global market, however, as with other countries, classification is not as simple as a single grading system.
Kenya
Kenyan coffee is graded from AA descending to C. Kenyan AA is considered high-quality specialty coffee since larger-sized beans produce more of the oils that provide its desired flavours.
There are also other grades, based on specific qualities and factors which are listed below:
Kenyan Coffee Grade | Description |
PB | Peaberries |
AA | Screens: 17 and 18 = 7.2 mm |
AB | Screens: 15 and 16 = 6.6 mm |
C | Screens: 14 and 15 |
E | Elephant (when the beans separate during processing, they are chipped and called “Ears”. This category also contains large “Peaberries”. |
TT | Light beans that are separated from AA and AB by air current |
T | Smaller than TT, many fragments. Light beans separated from C by air current |
UG | Ungraded: this involves all that does not fir the specific criteria for each official grade |
The Kenyan coffee grading system has served as a template for other African-origin countries such as Zambia, Uganda, and Burundi, although variations are expected for these other countries. However, the same requisites for larger screen-sized coffee carry across all of these systems, establishing a certificate of high-quality specialty coffee.
Zambia
Zambia uses a grading system which is very similar to Kenya, although there are some variations. One is the inclusion of the AAA grade, indicating the highest quality Zambian coffee.
Zambia’s specialty grades are AAA, AA, AB, and PB, while its lower grades are either for commercial use or considered very low-quality coffee.
Zambian Coffee Grade | Description |
AAA | Screen 19 |
AA | Screen 18 |
AB | Screen 16 |
C | Screen 14 |
PB | 4.5 slotted |
TT | Lights from AA and ABs |
T | Screen 12 |
E | Elephants |
Uganda
Ugandan coffee grades depend on whether arabica or robusta varietals are used. For arabica coffee, a lettered system is used, ranging from AA to peaberries and elephants.
High-grade Ugandan coffee is classified as either AA or A, making it similar to the Supremo/Excelso grades used in Colombian classification.
Ugandan arabica Grade | Grade Requirements |
AA | min. 90% milled above size 17, max 2% milled below 12 |
A | max. 10% milled above 17, max 2% milled below 12 |
B | max. 10% milled above 16, max 2% milled below 12 |
C | max. 10% milled above 15, max 5% milled below 12 |
PB | max. 5% milled above 16, max. 23% milled below 12 |
E | min. 85% milled above 19.5, max 5% milled below 12 |
Ugandan robusta Grade | Grade Requirements |
Natural : Screen 18 | min. 92% milled above 18, max. 1% milled below 12 |
Standard : Screen 17 | min. 90% milled above 17, max. 2% milled below 12 |
Screen 14 | max. 5% milled above 15, max 10% milled below 12 |
Screen 12 | max. 13% milled above 15, max 2% milled below 12 |
B.H.P. | type 1199 : sorting left-overs and small fragments usable Type 1013 : husks, dust |
Burundi
Burundi also uses a lettered system for grading its coffee and has precise requirements for each grade.
Burundi is currently working on developing its grading system, so much of its current requisites are recent. Some of the new specifications were introduced in 2020-21.
There are also plans to implement the names of regions in order to provide further transparency for commercial products.
Grade | Screen size (inch) | Retention in % | Defects | Brokens in % | Moisture % | Cup |
FW (Fully Washed) Ngmoa Mild | 18/64, 16/64, 14/64, or 10/64 | Min 60%>=16/64 | < 5 defects category 2 | 0 | 11.5 | Min 80% |
FW AA | 18/64 | 92% of 18/64 | Max 6% | <= 0.5 | 11.5 | Min 80% |
FW 15 | 18/64, 16/64, 15/64 | Min 60%>=16/64 | Max 6% | <= 1 | 11.5 | Min 80% |
FW A | 16/64 | 80%>=16/64, max 20% <16/64 | Max 8% | <= 1 | 11.5 | Min 80% |
FW PB | >=12/64 | Max 88%>=12/64 | Max 10% | <= 2 | 11.5 | Min 80% |
FW B | >=14/64 | Min 88% of 14/64 | Max 12% | <= 2 | 11.5 | Min 80% |
FW TT | Rejects of FW AA; FW A; FW 15 | Min 60% between 18/64 and 16/64 | Max 35% | Max 10 | 11.5 | Average 60% |
FW T | Rejects of FW B & FW PB | Average 80% of 14/64 | Max 40% | Max 10 | 11.5 | Average 50% |
FW Stocklot | All homogenous lots with 11.5% humidity but not corresponding with above mentioned specification and all rejects above 5% of over-fermented coffees. | |||||
FW Ngoma - SDL | Specialty coffee indicating the coffee mill |
Rwanda
Rwandan coffee follows a lettered system, similar to Kenya and Zambia. However, Rwandan coffee grades work differently from other lettered systems.
A - the highest grade - is split into A1, A2, and A3. These tiers consist of dense and heavy coffee beans, which hold the most essential oils and flavours. A1 designates the highest possible quality of Rwandan coffee. Then A2 and A3 designate specialty commercial grades. Below this are grades B and C, which are considered more or less low-grade coffee.
Rwandan coffee uses its own system for export. This involves assessing a sample of 350g and then incorporating a national green coffee grading system derived from ICO’s 2018 quality standards.
Regarding classifying Rwandan coffee in terms of defects, a numbered grade is given, and there are a few systems in place regarding the coffee processing method, as well as its varietal.
Fully Washed arabica Grade | Score | Description |
Superior Speciality | 80-90% | No more than 5 full defects in 350g of coffee. Primary defect permitted, maximum of 5% below screen size indicated, must possess at least one distinctive attribute in the body, flavour, aroma or acidity, must be free from cup faults and taints, no quakers. Moisture content between 10-12.5%. |
Grade 1 | 70-79% | No more than 9-23 full defects in 350g of coffee. No primary defect allowed, maximum of 5% below screen size indicated, must possess at least one distinctive attribute in the body, flavour, aroma or acidity, must be free from cup faults. Moisture content between 10-12.5%. |
Grade 2 | 60-69% | No more than 24-86 full defects in 350g of coffee. |
Grade 3 | 50-59% | More than 86 full defects in 350g of coffee. |
Semi Washed arabica Grade | Score | Description |
Grade 1 | 70-80% | No more than 23 full defects in 350g, primary defects are permitted, maximum of 5% below screen size, must possess at least a distinctive attribute in the body, flavour, aroma or acidity. No cup faults are permitted, only 3 quakers. Moisture content between 9-12.5% |
Grade 2 | 55-70% | No more than 30 full defects in 350g, primary defects are permitted, maximum of 5% below screen size, must possess at least a distinctive attribute in the body, flavour, aroma or acidity. No cup faults are permitted, only 3 quakers. Moisture content between 9-12.5% |
Grade 3 | 40-50% | 1-2 defective cups. No more than 50 full defects in 350g |
Grade 4 | <40% | More than 2 defective cups. More than 80 full defects in 350g |
robusta Grade | Score | Description |
Grade 1 | - | Fully washed |
Grade 2 | - | Semi Washed |