SCA Arabica Coffee Green Bean Grading Manual_ How to Grade Arabica Coffee Beans?

SCAA Standards for "Specialty Coffee" Green Coffee Beans

SCAA classifies green coffee defects into two major categories: Class I and Class II defects.

The requirements for the specialty coffee grade are:

1. No Class I defects

2. No more than 5 Class II defects

3. No "quakers" (0 quakers) in the roasted sample

4. The acceptable color range for green beans includes pale yellow, yellow-green, greenish, green, bluish-green, and blue-green. Per SCAA definitions, green coffee colors are categorized by origin, processing method, and aging time as brownish, yellowish, pale yellow, yellow-green, greenish, green, bluish-green, and blue-green — though beans that are too yellowish or brownish cannot qualify as specialty grade.

5. No off-flavors

Grading Standards

* Sample quantity: 350g of green beans, 100g of roasted beans

* Defect standards

* Important notes:

* Full Defect Equivalents (FDE) — different defects are counted in different units. One fully black bean counts as one Class I defect; two count as two. Severe insect damage is counted in units of 5: fewer than 5 does not count as a Class I defect, 5 or more but fewer than 10 counts as one, and so on. For Class II defects, partially sour and partially black beans are counted in units of 3, minor insect damage in units of 10, and all others in units of 5.

* Moisture content: for washed coffee, moisture should fall between 10-12%

* Bean size: no more than 5% deviation from contract specifications

* Roasting consistency: based on the 100g sample roast, no quakers allowed

* Additional grading notes: when two or more defects appear on the same bean, the more severe one takes precedence (for example, a partially sour bean bearing 2 insect holes is counted as a partially sour bean)

* Flavor characteristics: in the cupping sample, the beans must demonstrate regional character — dry and wet aroma, acidity, body, aftertaste, and overall quality

Below are detailed descriptions of each Class I and Class II defect.

Black Beans

* Physical characteristics: the most notable feature of a black bean is its opaque black appearance.

* Classification and scoring: black beans are divided into fully black and partially black according to the proportion of black area relative to the whole bean — less than half counts as partially black, otherwise fully black.

1 fully black bean counts as one Class I defect

3 partially black beans count as one Class II defect

* Impact on the cup: SCAA describes uncomfortable fermentation or foul odors — dirty, moldy, sour, and phenolic flavors. We have experienced nauseating mixes of sour and bitter, along with phenolic notes reminiscent of hospital disinfectant.

* Other issues: Ochratoxin A, which can harm the liver and kidneys. Research shows 80% of the toxin degrades during roasting (200°C), but it is best removed where possible.

* Causes: these defects arise during cultivation from a variety of factors:

Infection by the organic pathogen Colletotrichum coffeanum. First discovered in Africa, cases now also appear in Central and South American growing regions.

Insufficient water supply while the fruit matures, disrupting plant metabolism.

Unripe beans subjected to high-temperature drying (above 30°C).

* Prevention and improvement:

Cultivation: select mature cherries, improve the farming environment and methods, avoid creating conditions favorable to Colletotrichum coffeanum, improve ventilation, and promptly clear standing water around the trees.

Processing: black beans (after hulling) are smaller and lighter than normal beans, so they can be removed later through size and density sorting. The most effective method remains hand sorting — black beans are easy to spot once the parchment is off — or mechanical color sorting.

Sour Beans

* Physical characteristics: sour beans resemble pale yellow-brown or reddish-brown beans. Usually the endosperm point is black (as shown by the arrow in reference guides), and cutting the bean open reveals a vinegary, sharp smell.

* Classification and scoring: sour beans split into fully sour and partially sour, distinguished like black beans — less than half affected counts as partially sour, otherwise fully sour.

1 fully sour bean counts as one Class I defect

3 partially sour beans count as one Class II defect

* Impact on the cup: over-fermented sourness (nauseating).

* Causes: the main culprit is over-fermentation. In a relatively humid environment, ripe cherries left unpicked on the tree over-ferment; cherries stored too long after picking without timely processing also over-ferment; dirty fermentation tanks or dirty water in washed processing cause sour beans; and during drying, slow drying combined with improper stacking can trigger over-fermentation too.

* Prevention and improvement:

Cultivation: harvest ripe fruit (avoid overripe cherries), avoid picking fruit that has fallen to the ground, and avoid growing coffee at low latitudes near rivers, lakes, or reservoirs.

Processing: process picked cherries promptly to prevent over-fermentation in storage; control soaking time in fermentation tanks sensibly; replace washing water promptly rather than recycling it; manage drying properly. Most sour beans can be removed through hand sorting and color sorting.

Moldy Beans

* Physical characteristics: moldy beans look similar to sour beans — yellow or reddish-brown — but the telltale difference is a small concave spot bearing some white powdery substance. That powder is mold spores, which can easily contaminate other green beans.

* Classification and scoring:

1 moldy bean counts as one Class I defect

* Impact on the cup: an earthy, moldy taste with phenolic notes. To us it resembles black beans — a pronounced earthiness, like biting a bad roasted melon seed, with a rough sandy texture and bitterness. Like black beans, moldy beans carry an Ochratoxin A health risk.

* Causes: moldy beans can occur during cultivation or after processing. Under certain temperature and humidity conditions, the responsible molds grow readily on green coffee.

* Prevention and improvement:

Cultivation: mold needs spores first, so limiting spore formation is key. Avoid picking fruit off the ground, and don't leave green beans sitting in harvest baskets or drying drums.

Processing: green beans cut during pulping are especially susceptible to mold. Poor fermentation control, delayed or interrupted drying, or excessively long drying all invite infection, and parchment stored warm and humid is likewise vulnerable. Adjusting processing and storage properly prevents most moldy beans. Color sorting removes the most severely moldy beans; slightly moldy ones must be caught by hand sorting.

Foreign Matter and Impurities

* Physical characteristics: large foreign objects are easy to spot visually, but small stones are hard to pick out of a batch of green beans quickly — auxiliary equipment is needed to remove impurities and protect roasters and grinders.

* Classification and scoring:

1 foreign object counts as one Class I defect

* Impact on the cup: some foreign matter taints the beans and flawed flavors follow.

* Other impacts: the more direct danger falls on the roaster drum and grinder burrs — stones above all.

* Causes: foreign matter can enter at any stage of processing (mostly through human factors).

* Prevention and improvement:

During processing, avoid introducing small stones, twigs, and other debris at picking; while sun-drying on racks, keep stones, wood splinters, and the like out; and after drying, destoners and magnets at hulling effectively remove stones, metals, and other foreign objects.

Dried Coffee Pods

* Physical characteristics: dried coffee pods are whole coffee fruits that were never removed from the green beans after drying. They are much larger than green beans and range in color from yellow-brown to dark red; if drying, storage, or transport conditions are poor, they mold easily and can affect the beans around them.

* Classification and scoring:

1 dried coffee pod counts as one Class I defect

* Impact on the cup: fermented, moldy, and phenolic flavors.

* Causes:

Processing: in washed coffee, improper pulp removal (wrong settings or worn machines that let dried pods pass straight through) or failing to skim floating dried pods during the initial rinse. In natural processing, careless hulling and sorting can also leave dried pods behind.

Cultivation: drought and disease can dry fruit on the tree until it eventually drops.

* Prevention and improvement:

Cultivation: avoid picking dried fruit off the ground, and avoid picking fruit that has already dried on the tree.

Processing: prevent excessive dried pods from entering the huller — too many jam the machine and let pods slip through. During the initial washing stage, skim all floaters, and regularly adjust and maintain pulpers so pulp and dried pods are effectively removed. Pods that slip through can be removed after drying with density machines.

Insect-Damaged Beans

* Physical characteristics: insect-damaged beans show small holes (0.3-1.5 mm in diameter) on the surface. Because the insect tunnels in and out, there are usually holes on both sides. Severe damage sometimes merges several holes into one area. Like broken beans, damaged beans oxidize and mold easily at the damaged spots.

* Classification and scoring: insect damage is graded as severe or minor.

Severe: beans with 3 or more holes — 5 severely damaged beans count as one Class I defect.

Minor: beans with fewer than 3 holes — 10 minorly damaged beans count as one Class II defect.

* Impact on the cup: dirty taste, sourness, phenolic and moldy flavors.

* Causes: all insect damage originates in cultivation. Coffee berry borers drill into the beans to lay eggs, and the larvae live inside the bean, consuming its nutrients. Holes usually appear in pairs — one entrance, one exit.

* Prevention and improvement:

Cultivation: diligent pest monitoring to eliminate conditions favorable to the borer; pesticide spraying is an option but of limited effectiveness. More and more regions now use newer approaches — insect traps and natural predators of the borer — to control the pest more effectively. Because the borers live inside the fruit and beans, farmers cannot distinguish damaged from healthy cherries at picking. Growing at higher altitudes significantly reduces borer pressure.

Processing: insect-damaged beans are easier to identify after hulling. Density machines remove most severely damaged beans; when infestation is heavy, hand sorting is essential.

Broken and Cut Beans

* Physical characteristics: green beans show mechanical damage — cracks, breaks — sometimes with blackened edges.

* Classification and scoring

5 broken beans count as one Class II defect

* Impact on the cup: where mold is present, a noticeable earthy moldiness plus dirty, sour, fermented flavors.

* Causes: poorly adjusted pulpers or hullers squeeze, damage, or cut the beans.

In washed processing, crushing damage from pulping molds and oxidizes easily, usually turning dark reddish-brown or black.

In natural processing, breaks usually happen during hulling of dried cherries and are generally clean, without oxidation.

* Prevention and improvement:

Cultivation: avoid picking unripe cherries.

Processing: adjust pulpers and hullers carefully. Small broken beans can be removed with density machines and screens; larger ones require color sorting and hand sorting.

Unripe Beans

* Physical characteristics: the hallmark of an unripe bean is silver skin that clings more tightly. Unripe beans are usually smaller than normal, with concave bodies and sharper edges. In roasted coffee, unripe beans are called QUAKERS: because the immature green bean never accumulated enough sugar, caramelization (browning) falls short during roasting, and the bean finishes much paler than the rest.

* Classification and scoring: 5 unripe beans count as one Class II defect

* Impact on the cup: grassy, straw-like flavors.

* Causes: all unripe beans originate in cultivation — careless picking, or planting late-maturing varieties at high altitude.

* Prevention and improvement:

Cultivation: pick only ripe cherries; plant varieties whose maturation suits the altitude.

Processing: because the skin of an unripe cherry clings tighter than normal, pulping removes little or none of it — some unripe fruit passes through entirely. After pulping, screens catch unripe beans quickly; after drying, density machines remove them too. Note that because unripe beans show no meaningful color difference from normal green beans, color sorters cannot remove them.

Withered Beans

* Physical characteristics: withered beans are smaller than normal, with a dehydrated, wrinkled appearance like a raisin — think of how skin wrinkles after too long in water.

* Classification and scoring: 5 withered beans count as one Class II defect

* Impact on the cup: a slight grassy, straw-like flavor.

* Causes: withered beans come only from cultivation, mostly drought leaving the trees unable to deliver nutrients to the fruit.

* Prevention and improvement:

Cultivation: fertilize properly so the trees grow healthily; note that too many shade trees — or the wrong ones — compete with coffee for water.

Processing: severely withered beans are so light they float during washed processing and are easy to skim off; after hulling, density machines remove most of the rest, while the occasional larger or thicker withered bean must be picked out by hand.

Shell Beans

* Physical characteristics: shell beans (elephant beans) have two parts — the outer part is usually called the "shell," while the inner part is conical or cylindrical. Sometimes the two halves remain attached in green coffee: attached, it counts as 1 shell bean; separated, 2. Most separate during roasting, and the lighter outer shell scorches easily.

* Classification and scoring: 5 shell beans count as one Class II defect

* Impact on the cup: a scorched taste — the beans' low density makes them scorch or even burn at roasting temperatures.

* Causes: current research points mostly to genetic factors.

* Prevention and improvement:

Cultivation: select suitable varieties and optimize growing conditions.

Processing: remove shell beans with density machines at hulling.

Floating Beans

* Physical characteristics: floating beans are much lighter and whiter than normal beans, and float in water.

* Classification and scoring: 5 floating beans count as one Class II defect

* Impact on the cup: depending on severity, fermented, grassy, straw, earthy, or moldy flavors.

* Causes: improper storage and drying are the main culprits. Parchment left in dryers or on drying racks commonly produces floaters, as does storing parchment in humid conditions.

* Prevention and improvement:

Processing: parchment must be dried evenly to the target moisture content to prevent floaters. After hulling, low-density floaters are removed with density machines; high-density floaters weigh so close to normal beans that only color sorting or hand sorting can remove them.

Parchment Beans

* Physical characteristics: parchment beans remain fully or partially covered by their parchment shell, which appears earthy yellow.

* Classification and scoring: 5 parchment beans count as one Class II defect

* Impact on the cup: woody taste (if parchment beans make up a large share of the batch, the woody note becomes very obvious).

* Causes: mainly in the post-drying de-parchment stage — worn or badly adjusted machines let beans slip through unshelled.

* Prevention and improvement:

Processing: check and adjust de-parchment machines before hulling. The separated shells can be removed with density machines.

Husk and Shell

* Physical characteristics: husk and shell appear as fragments among the green beans, in colors from dark red (like a dried raisin).

* Classification and scoring: 5 husks (shells, or outer skin) count as one Class II defect

* Impact on the cup: mold-infected husks produce dirty, earthy, moldy, fermented, or phenolic flavors.

* Causes: mainly in processing — green coffee not cleaned carefully after hulling leaves shell residue behind, and in washed processing a badly adjusted pulper can break husk into fragments that dry into shell pieces.

* Prevention and improvement: adjust the pulpers; pay attention to winnowing and density sorting so no shells slip through.

FrontStreet Coffee Recommendation

All of this grading talk comes down to one thing: a cleaner, sweeter cup. Here are the washed specialty beans FrontStreet Coffee most recommends, drawn from our house notes:

FrontStreet Coffee Yirgacheffe Guodingding Cooperative

Everyone knows Yirgacheffe, but fewer know that because local smallholder yields are tiny, farmers send their cherries to cooperatives for joint processing and sale. The Guodingding Cooperative is an outstanding processing team from Guodingding village, with practiced, experienced hands whose coffee was "discovered" precisely because it is so refined and clean. Washed processing lets the lot show jasmine florals and bright citrus acidity to the fullest; roasted medium-light, it also unfolds green tea and honey notes, and it takes happily to pour-over, cold brew, or espresso.

FrontStreet Coffee Kenya Cherry Tomato

When washed processing comes up, our Kenya Cherry Tomato is one of the best-known representatives, because Kenya excels at double-washed processing: an extra wash cycle — flotation, soaking, washing the mucilage off the bean surface, another soak, then drying on raised beds before hulling and storage. All that repeated washing and soaking presents the coffee's juice-like character in the extreme: cherry tomato, dried plum, snow pear, black plum, and yellow sugar in a sweet-tart, juicy cup — a long-standing favorite among coffee enthusiasts.

FrontStreet Coffee Jamaica Blue Mountain No. 1

Jamaica, one of the most famous coffee origins of its era, suffered from limited sunshine — its island climate gives it shorter days than other regions. To lower the risk of beans spoiling, washed processing was born there. The key difference from natural processing is that the skin, pulp, and mucilage are removed before drying, cutting the moisture wrapped around the bean and shortening drying time; the resulting beans are translucent in color with a low defect rate. Washed processing is what guarantees Blue Mountain's rich aroma: in the cup it shows hazelnut, cream, chocolate, and caramel with a perfectly even balance — no single flavor leaping out, none missing.