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

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SCAA Standards for 'Specialty Coffee' Green Coffee Beans

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

The requirements for specialty coffee grade are:

❶ No Class I defects

❷ No more than 5 Class II defects

❸ No 'quakers' (0 quaker) in roasted coffee beans

❹ The acceptable color range for green coffee beans includes pale yellow, yellow-green, greenish, green, bluish-green, and blue-green. According to SCAA definitions, green coffee bean colors are categorized based on origin, processing method, and aging time as: brownish, yellowish, pale yellow, yellow-green, greenish, green, bluish-green, and blue-green (where lighter yellowish and brownish beans cannot qualify as specialty grade)

❺ No off-flavors

Grading Standards

▶ Sample quantity: 350g green beans, 100g roasted beans

▶ Defect standards

★ Important note:

▶ Full Defect Equivalents (FDE) - the counting unit for different defects varies. For example: one fully black bean counts as one Class I defect, two count as two Class I defects; severe insect damage is counted in units of 5 - if fewer than 5 are found, it doesn't count as a Class I defect, but if 5 or more but fewer than 10 are found, it counts as one Class I defect, and so on; for Class II defects, partially sour or partially black beans are counted in units of 3, while minor insect damage is counted in units of 10, with all others counted in units of 5.

▶ Moisture content: For washed processed coffee, moisture content should be between 10-12%

▶ Bean size: Cannot exceed 5% deviation from contract specifications

▶ Roasting consistency: Based on 100g sample roasting standard, no quakers allowed

▶ Additional grading notes: When two or more defects appear simultaneously, the more severe one takes precedence (for example, if partially sour beans are present along with 2 insect holes, the defect is counted as partially sour beans)

▶ Flavor characteristics: In cupping samples, beans must demonstrate regional flavor characteristics, including dry and wet aroma, acidity, body, aftertaste, and overall quality

The following are detailed descriptions of each defect (Class I and Class II).

Black Beans

▶ Physical characteristics: The most notable feature of black beans is their opaque black appearance

▶ Classification and defect scoring: Black beans are categorized as fully black or partially black based on the proportion of black area relative to the entire coffee bean (if the black area is less than half the bean body, it's treated as partially black, otherwise as fully black)

1 fully black bean counts as one Class I defect

3 partially black beans count as one Class II defect

▶ Impact on cup quality: SCAA describes uncomfortable fermentation or foul odors, dirty, moldy, sour, and phenolic flavors. I've experienced nauseating uncomfortable sour and bitter mixed flavors, along with phenolic tastes similar to hospital disinfectant

▶ Other issues: Ochratoxin A, which can harm liver and kidneys. Research shows that 80% of toxins degrade during roasting (200°C), but it's best to remove them when possible

▶ Causes: These defects occur during cultivation due to various 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 during coffee fruit maturation affects plant metabolism

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

▶ Prevention and improvement:

Cultivation: Select mature coffee fruits, improve farming environment and methods, avoid creating suitable conditions for Colletotrichum coffeanum, improve ventilation, and promptly clear standing water around coffee trees

Processing: Black beans (after hulling) are smaller and lighter than normal beans, so in later processing they can be removed through size sorting and density sorting. The most effective method remains hand sorting (black beans are easily identifiable after removing parchment), or mechanical color sorting

Sour Beans

▶ Physical characteristics: Sour beans appear similar to pale yellow-brown or reddish-brown in color. Usually, the endosperm point is black (as indicated by the arrow), and a vinegary sharp smell can be detected when cutting the bean open

▶ Classification and defect scoring: Sour beans are divided into fully sour and partially sour categories, with distinction methods similar to black beans - if less than half the bean body is affected, it's classified as partially sour, otherwise as fully sour

1 fully sour bean counts as one Class I defect

3 partially sour beans count as one Class II defect

▶ Cup impact: Over-fermented sour taste (nauseating)

▶ Causes: The main cause of sour beans is over-fermentation. If the coffee environment is relatively humid, ripe coffee fruits not picked promptly from the tree will over-ferment; coffee fruits stored too long after picking without timely processing will also over-ferment; dirty fermentation tanks or water in washed processing can also cause sour beans; during drying, if coffee fruits dry slowly combined with improper stacking, this can also cause over-fermentation and formation of sour beans

▶ Prevention and improvement:

Cultivation: Harvest ripe fruits (avoid harvesting overripe coffee fruits), avoid picking coffee fruits that have fallen to the ground, and avoid growing coffee at low latitudes near rivers, lakes, or reservoirs

Processing: Process picked coffee fruits promptly to avoid over-fermentation during storage; reasonably control soaking time in fermentation tanks; replace water promptly during washing process to avoid recycling; properly control drying process; most sour beans can be removed through hand sorting and color sorting

Moldy Beans

▶ Physical characteristics: Moldy beans have a color similar to sour beans - yellow or reddish-brown - but a distinct difference is that moldy beans have a small concave spot with some white powdery substance at the spot. These powders are mold spores, which can easily contaminate other green beans

▶ Classification and defect scoring:

1 moldy bean counts as one Class I defect

▶ Cup impact: Earthy moldy taste, phenolic flavor. Personally, I feel it's somewhat similar to black beans, with a noticeable earthy taste in the mouth, similar to eating a bad roasted melon seed, with a distinct rough sandy texture and bitterness. Like black beans, there's a physiological health risk from Ochratoxin A

▶ Causes: Moldy beans can occur during cultivation and post-processing. The mold that causes moldy beans can grow and infect green coffee beans under certain temperature and humidity conditions

▶ Prevention and improvement:

Cultivation: The prerequisite for mold growth is spores, and limiting spore generation is key to preventing mold growth. During cultivation, avoid picking coffee fruits that have fallen to the ground, and avoid leaving green coffee beans in harvesting baskets and drying drums

Processing: Green beans cut during pulp (skin) removal are more susceptible to mold infection. Improper fermentation control, delayed drying, interrupted drying, or extended drying periods can all create opportunities for mold infection. Additionally, parchment beans stored at higher temperatures and humidity are more susceptible to mold infection. Proper adjustment of processing and storage methods can largely prevent moldy beans. Color sorting can remove most severely moldy beans, while slightly moldy beans must be effectively removed through hand sorting

Foreign Matter Impurities

▶ Physical characteristics: Large foreign matter is relatively easy to identify visually, but small stones are generally difficult to quickly identify from green beans, requiring auxiliary equipment to remove impurities and avoid risks to roasters and grinders

▶ Classification and defect scoring:

One foreign object counts as one Class I defect

▶ Cup impact: Some foreign matter can affect green beans, causing flawed flavors in the cup

▶ Other impacts: The more direct impact of foreign matter is on the roaster (drum) and grinder (burrs), such as stones

▶ Causes: Foreign matter can be introduced at various stages of processing (mostly due to human factors)

▶ Prevention and improvement:

During processing, avoid introducing small stones, branches, and other debris when picking; during natural drying on racks, carefully avoid introducing stones, wood strips, and other foreign matter; during hulling after drying, destoners and magnets can effectively remove stones, metals, and other foreign matter

Dried Coffee Pods

▶ Physical characteristics: Dried coffee pods are generally whole coffee fruits that have not been removed from green beans after drying. They are much larger than green beans and appear in colors ranging from yellow-brown to dark red; if conditions are improper during drying, storage, or transportation, they are more susceptible to mold infection, affecting other green beans

▶ Classification and defect scoring:

One dried coffee pod counts as one Class I defect

▶ Cup impact: Fermentation, moldy, and phenolic flavors

▶ Causes:

Processing: In washed processing, improper pulp removal (imper settings or aging machines that allow dried pods to pass directly), or failure to completely remove floating dried pods during the initial rinsing process. In natural processing, improper hulling and sorting can also miss some dried pods

Cultivation: Drought and disease can cause coffee fruits to dry on trees and eventually fall to the ground

▶ Prevention and improvement:

Cultivation: Avoid picking dried coffee fruits that have fallen to the ground, and avoid picking coffee fruits that have already dried on trees

Processing: Avoid excessive dried pods being mixed with green beans during hulling, as too many dried pods can prevent hullers from effectively processing coffee fruits, thus missing some dried pods; During the initial washing stage, completely remove floating beans, and regularly adjust and maintain pulping machines to effectively remove pulp and dried pods. Missed dried pods can be removed during post-drying hulling using density machines

Insect-Damaged Beans

▶ Physical characteristics: Insect-damaged beans show small holes (diameter 0.3-1.5 mm) on the surface. Since insects burrow in and out, there are usually holes on both sides. Severe insect damage sometimes has several small holes connected into one area. Like broken beans, damaged beans are easily oxidized and infected with mold in the insect-damaged areas

▶ Classification and defect scoring: Insect damage is categorized as severe or minor

Severe insect damage: Beans with 3 or more insect holes - when there are 5 severely insect-damaged beans, they count as one Class I defect

Minor insect damage: Beans with fewer than 3 insect holes - when there are 10 minorly insect-damaged beans, they count as one Class II defect

▶ Cup impact: Dirty taste, sourness, phenolic and moldy flavors

▶ Causes: Insect-damaged beans are all produced during cultivation. Coffee borers drill into coffee beans to lay eggs, and the larvae parasitize the coffee beans, absorbing their nutrients. Insect holes in coffee beans usually appear in pairs (one entry, one exit)

▶ Prevention and improvement:

Cultivation: Meticulous pest and disease inspection to eliminate all conditions favorable to coffee borers; pesticide spraying is also an option but with limited effectiveness. Currently, more growing regions are adopting new technologies such as insect traps and natural enemies of coffee borers to more effectively eliminate pests. Since coffee borers are inside coffee fruits and beans, farmers cannot distinguish between insect-damaged and normal coffee fruits during picking. Growing at higher altitudes significantly reduces coffee borer impact

Processing: Insect-damaged coffee beans are more easily identifiable after hulling. Most severely insect-damaged beans can be removed with density machines. If insect damage is severe, hand sorting must be used for removal

Broken and Cut Beans

▶ Physical characteristics: Green beans show mechanical damage such as cracks or breaks, sometimes with blackened edges

▶ Classification and defect scoring

5 broken beans count as one Class II defect

▶ Cup impact: If mold is present, there's a noticeable earthy moldy taste, dirty flavor, sourness, and fermentation taste

▶ Causes: Improper adjustment of pulpers or hullers during processing causes beans to be squeezed, damaged, or cut

In washed processing, breaks from squeezing during pulping are more susceptible to mold infection and oxidation, usually turning dark reddish-brown or black

In natural processing, breaks usually occur during dried fruit hulling and are generally clean without oxidation traces

▶ Prevention and improvement:

Cultivation: Avoid picking unripe coffee fruits

Processing: Carefully adjust pulpers and hullers; small broken beans can be removed with density machines and screens, while large broken beans must be removed through color sorting and hand sorting

Unripe Beans

▶ Physical characteristics: The notable feature of unripe beans is that their silver skin adheres more tightly. Unripe beans are usually smaller than normal green beans, with concave bodies and sharper edges. Another name for unripe beans is QUAKERS in roasted coffee beans - this is because unripe green beans haven't fully matured, leading to insufficient sugar absorption. During roasting, caramelization (coloring) is insufficient, resulting in a final color much lighter than normal beans

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

▶ Cup impact: Grassy taste, straw flavor

▶ Causes: Unripe beans are all produced during cultivation, such as improper picking and planting late-maturing coffee varieties in high-altitude areas

Prevention and improvement:

Cultivation: Improve picking quality, only pick ripe beans; plant suitable maturity varieties based on altitude

Processing: Since the pulp (skin) of unripe beans adheres more tightly to coffee beans than normal ripe coffee fruits, during pulping, only a small portion of the skin will be removed from unripe beans, or even the entire coffee fruit may be missed. After pulping, unripe beans can be quickly removed through screens. After drying, unripe beans can also be removed with density machines; it's worth noting that since unripe beans have no significant color difference from normal green beans, color sorters cannot remove them

Withered Beans

▶ Physical characteristics: Withered beans are smaller than normal beans, with the most notable feature being a dehydrated wrinkled appearance, similar to raisins (think of how skin wrinkles when soaked in water for too long)

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

▶ Cup impact: Slight grassy taste, straw flavor

▶ Causes: Withered beans are only produced during cultivation, mostly due to drought causing poor coffee tree development, unable to deliver necessary nutrients to coffee fruits

▶ Prevention and improvement:

Cultivation: Proper fertilization to ensure healthy coffee tree growth; too many or inappropriate shade trees can also compete with coffee trees for water

Processing: Severely withered beans are light and float directly on water during washed processing, making them relatively easy to scoop out; during hulling, remaining withered beans can mostly be removed with density machines, while individual larger or thicker withered beans must be removed by hand sorting

Shell Beans

▶ Physical characteristics: Shell beans have two parts - the external part is usually called "shell-shaped," while the internal part is either conical or cylindrical. Sometimes, the two parts of shell beans in green beans remain relatively tightly attached together - in this case, it counts as 1 shell bean, but if they've separated, it counts as 2. Most shell beans separate into two parts after roasting, and the lighter external "shell" part is more easily scorched during roasting

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

▶ Cup impact: Scorched taste (because shell beans have low density and are easily scorched or even burned by high temperatures during roasting)

▶ Causes: Current research suggests that shell beans are mostly caused by genetic factors

▶ Prevention and improvement:

Cultivation: Select suitable coffee varieties for cultivation and optimize growing conditions

Processing: During hulling, use density machines to remove shell beans

Floating Beans

▶ Physical characteristics: Floating beans are much lighter and whiter in color compared to normal beans, and float when placed in water

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

▶ Cup impact: Depending on severity, can have fermented, grassy, straw, earthy, or moldy flavors

▶ Causes: Improper storage and drying are the main causes of floating beans. Parchment beans left in dryers or on drying racks usually lead to floating beans. Storing parchment beans in high humidity environments also causes floating beans

▶ Prevention and improvement:

Processing: Parchment beans must be uniformly dried to a certain moisture content to avoid floating bean production. After hulling, low-density floating beans can be removed with density machines, while high-density floating beans have little weight difference from normal beans and can only be removed through color sorting or hand sorting

Parchment Beans

▶ Physical characteristics: Parchment beans are usually fully or partially covered by parchment shell, with the shell appearing in earthy yellow color

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

▶ Cup impact: Woody taste (if parchment beans account for a large proportion, the woody taste will be very obvious)

▶ Causes: Mainly during the post-drying de-parchment process, aging or improperly adjusted de-parchment machines can cause parchment beans to be missed

▶ Prevention and improvement:

Processing: Check and adjust de-parchment machines before hulling. Separated bean shells (parchment) can be removed with density machines

Husk and Shell

▶ Physical characteristics: Husk or shell usually appear as fragments in green beans, with colors ranging from dark red (like dried raisin color)

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

▶ Cup impact: If husks are infected with mold, they will produce dirty, earthy, moldy, fermented, or phenolic flavors in the cup

▶ Causes: Mainly during the processing stage, failure to carefully clean green beans after hulling leads to residual shells. In washed processing, improper pulper adjustment can also cause husk fragments to break up and eventually become shell fragments after drying

▶ Prevention and improvement: Adjust pulpers; pay attention to winnowing and density sorting processes to avoid missing shells

● Arabica Coffee Bean Brand Recommendations

FrontStreet Coffee's roasted Arabica coffee beans are fully guaranteed in both brand and quality. More importantly, they offer extremely high value for money - each 227-gram pack costs only around 70-90 yuan. Calculating at 15 grams of coffee beans per cup, one pack can make 15 cups of coffee, with each cup costing only about 5-6 yuan. Compared to cafes selling cups for over 100 yuan, this is truly a conscientious recommendation.

FrontStreet Coffee: A roastery in Guangzhou with a small storefront but diverse bean varieties, where you can find various famous and lesser-known beans. They also provide online store services. https://shop104210103.taobao.com

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473