Demystifying Ugandan Green Coffee Grading: Screen Sizes, Defect Limits, and UCDA vs. SCA Standards
By Sandra Nansbuga
Demystifying Ugandan Green Coffee Grading: Screen Sizes, Defect Limits, and UCDA vs. SCA Standards
Uganda green coffee grading standards are set out in Uganda Standard DUS 1957, which grades coffee by screen size, weight-based defect tolerance, and moisture content, a framework built on physical measurement rather than the defect-count-and-cupping approach used in specialty coffee circles. The two systems measure different things, so mapping a Ugandan grade like Screen 18 to a specialty-grade claim requires understanding both frameworks rather than assuming the terms are interchangeable.
How UCDA's screen and defect standards work
Under Uganda Standard DUS 1957, notified to the World Trade Organization's Technical Barriers to Trade Committee by the Uganda National Bureau of Standards, dry-processed Robusta grades are defined primarily by sieve retention. Screen 18 requires at least 90% of beans by weight retained on the Screen 18 sieve, with a tolerance of up to 10% passing through to Screen 17, and caps moisture content at 12.0%. Screen 15 requires at least 90% retention on the Screen 15 sieve, permits up to 12% defective beans by weight, allows up to one-tenth of one percent extraneous matter, and caps moisture at 12.5%. Broken Hand-Picked (BHP), a lower grade used in industrial and soluble manufacturing, requires only 85% retention on Screen 12 and permits up to 20% defective beans by weight, a materially wider tolerance than the higher-screen grades.
This is a weight-and-sieve system: coffee is graded by how much of a sample, by physical weight, sits above a given screen size and how much of it, by weight, is defective. It does not directly measure cup quality.
How the specialty coffee industry's grading language differs
The Specialty Coffee Association's own current standards page lists a formal green coffee grading standard, SCA-110, as still under development rather than a currently published SCA standard. The defect-count-and-cupping framework widely referenced across the industry, zero primary defects and no more than five secondary defects per 350-gram sample, paired with a cupping score of 80 or above to qualify as specialty grade, traces to the legacy SCAA Green Coffee Classification system that predates the current SCA and remains in common industry use even though it is not, as of this writing, a currently published SCA standard.
Uganda has its own version of this defect-and-cupping approach specifically for Robusta. The Coffee Quality Institute's account of its work in Uganda states that in 2014, the Uganda Coffee Development Authority and CQI jointly published the industry's first comprehensive standard defining Fine Robusta, built on defect-count and cupping principles similar to those used for specialty Arabica, requiring zero primary defects and no more than five secondary defects in a 350-gram sample plus a cupping score of 80 or above.
What this means for buyers
A UCDA screen grade and a specialty-grade claim answer different questions. Screen 18 tells a buyer about bean size and weight-based defect tolerance under DUS 1957. It says nothing on its own about cupping score. A lot can meet Screen 18's sieve and moisture requirements without meeting the CQI/UCDA Fine Robusta defect-count and cupping thresholds, and vice versa in principle, so buyers evaluating both size and cup quality need documentation against both frameworks, not one used as a proxy for the other.
"SCA grade" claims for Ugandan lots should be checked against which framework is actually meant. Because SCA's own formal green coffee grading standard is still in development, a supplier describing a lot as meeting "SCA specialty grade" is very likely referencing the legacy SCAA defect-and-cupping framework rather than a currently published SCA document. Asking a supplier to specify which framework, and provide the underlying defect count or cupping score, avoids ambiguity.
Screen size and defect tolerance move independently. Since BHP permits a defect tolerance more than 1.6 times wider than Screen 15's, and roughly double what Screen 18 implies, buyers substituting between grades to manage cost should evaluate the actual defect and cup impact of that gap rather than treating screen numbers as a simple quality ladder.
FAQ
What is the maximum moisture content for Uganda Screen 18 Robusta?
Uganda Standard DUS 1957 sets a maximum moisture content of 12.0% for Screen 18 dry-processed Robusta.
Has the SCA published an official green coffee grading standard?
As of this writing, the SCA's own standards page lists a formal green coffee grading standard, SCA-110, as still under development rather than published.
What defect and cupping thresholds define Fine Robusta from Uganda?
The CQI/UCDA Fine Robusta standard, published in 2014, requires zero primary defects, no more than five secondary defects in a 350-gram sample, and a cupping score of 80 or above.
Sources
Uganda National Bureau of Standards, DUS 1957
Specialty Coffee Association, Standards
Coffee Quality Institute, Uganda
Sources: Uganda Standard DUS 1957 | Specialty Coffee Association's own current standards page | Coffee Quality Institute's account of its work in Uganda