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3.5 FINAL PROCESSING FOR EXPORT AND ROASTING
3.7.1 Characterization of defects
Coffee beans are considered normal when they produce a drink capable of satisfying the consumer. Common market usage is that coffee beans without defects make a sound lot. A defect is anything that diverges from a normal bean inside the lot and that can be produced in the field or during the harvest, processing, transport and storage. In commercial use, it is defined as the number of defective beans and foreign matter present in specific green coffee samples, normally in 300–500 g, or 1000 beans.
Most producing countries have their own criteria for the classification of coffee, based on the sum of specific defects, each of which is evaluated in The raw bean 117
Table 3.3 Threshold level in water of the most odorous chemicals present in defective beans
Odorant Odour threshold in water (lgl1) 2,4,6-trichloroanisole 0.001
2-methylisoborneol 0.0025
geosmin 0.005
Source: R. Viani, 2003
accordance with established commercial criteria. In an effort to cover all coffee types in a general norm, the International Organization for Standardization (ISO) has produced in the past Standard 10470-1993 – Green Coffee – Defect Reference Chart (ISO, 1993), which met with little utilization. This standard is currently in the final stage of a revision process that aims at a simple and more precise enforcement. Along with a reorganized chart of defects, now also shown in photographs, the main new concepts introduced will be:
n Defects are grouped in five classes, namely
n non-coffee defects (foreign matter) (see 3.7.1.1 and Table 3.4);
n defects of non-bean origin (e.g., husks/hulls) (see 3.7.1.2 and Table 3.5);
n irregularly formed beans (e.g., ears/shells/broken beans/nipped beans) (see 3.7.1.3 and Table 3.6);
n beans with an irregular visual appearance, with risk of influenc-ing cup taste) (see 3.7.1.4 and Table 3.7);
Table 3.4 Defects associated with foreign matter
Name
Characteristics/
definition Causes
Brew flavour/
roasting Origin Stone* Stone of any diameter
found in a green
Stick* Twig of any diameter found in a green
Abbreviations: WPA, wet-processed arabica; WPR, wet-processed robusta; DPA, dry-processed arabica; DPR, Dry-processed robusta.
H, Harvest-damaged beans: inadequate crop management (picking cherries before or after maturation, cherries from the ground, etc.)
P, Process-damaged beans: defects due to imperfect processing operations (pulping, washing, drying, cleaning, hulling, etc.).
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Table 3.5 Defects associated with fruit parts
Name and one or more beans
Incorrect dehusking,
P, Process-damaged beans: defects due to imperfect processing operations (pulping, washing, drying, cleaning, hulling, etc.).
n off-tastes (defects identifiable on cup testing only) (see 3.7.1.5 and Table 3.8).
n Quantifying defects by weight, to allow for exact calculations to be applied to any contract of purchase of green coffee that may be negotiated between provider and client.
Defects can modify cup quality leading to unpleasant flavours, the loss of product due to the presence of foreign matter or the burning of fragments or small beans in the roaster. Some defects, such as mouldiness, which can produce toxins, can also affect consumers’ health. Many defects may appear equally in wet-processed arabica (WPA), wet-processed robusta (WPR), dry-processed arabica (DPA) and dry-processed robusta (DPR). Other
EspressoCoffee
Part of bean originated from the elephant bean: shell or ear – external part of the elephant bean presenting a cavity; shell core – internal part of the elephant bean
Splitting of the elephant bean (growth defect) generally through handling (dehulling or dehusking), producing the separation of the inner and outer parts
Uneven roast;
slight bitterness;
less acidity
F/P
Bean fragment* Fragment of a coffee bean of volume less than half a bean
Formed mainly during faulty dehulling, dehusking or pulping operations. Over-drying making beans easily breakable during handling
Uneven roast;
bitterness; less acidity
P
Broken bean* Fragment of a coffee bean of volume equal to or greater than half a bean
Formed mainly during faulty dehulling, dehusking or pulping operations.
Over-drying making beans easily breakable during handling
Uneven roast;
bitterness; less acidity
P
Insect-damaged bean* Coffee bean damaged internally or externally by insect attack
Attack on cherries by Hypothenemus haempei (coffee berry borer)
Increased bitterness; less acidity
F
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Insect-infested bean*
Coffee bean containing one or more live or dead insects at any stage of development
Bean attacked by storage pests, generally Araecerus fasciculatus insect
Loss of flavour;
slight bitterness S
Pulper-nippedy
pulper-cut beany Wet-processed coffee bean cut or bruised during pulping, often with brown or blackish marks
Faulty adjustment of pulping machine or feeding with under-ripe cherries or malformed beans
Non-specific downgrading to slightly putrid or stinker
P
Crushed bean* Crushed beans often partly split and faded with centre-cut largely open
Treading on the beans during drying.
Hulling or polishing of soft under-dried beans
Non-specific downgrading to rancid, slightly fermented
P
*Found in WPA/WPR/DPA/DPR.
yFound in WPA/WPR.
Abbreviations: WPA, wet-processed arabica; WPR, wet-processed robusta; DPA, dry-processed arabica; DPR, Dry-processed robusta.
F, Field-damaged bean: defects originating in the field, the coffee tree (genetic problems), the environment (climate, soil, water and nutrient stress), attacks by pests and diseases.
P, Process-damaged beans: defects due to imperfect processing operations (pulping, washing, drying, cleaning, hulling, etc.).
S, Storage damaged beans: defects due to deficient storage (faulty storage practices and storage pests).
EspressoCoffee
Name Characteristics/definition Causes Brew flavour/roasting Origin
Black bean* Coffee bean whose interior is partly (partly black bean) or totally black (endosperm).
Bean from over-ripe cherry, fallen on the ground.
Due to Colletotrichum coffeeanum attack, other fungi species and pests. Carbohydrate deficiency bean due to poor cultural practices. Mature cherries subjected to over-fermentation by moulds/yeasts and subsequent drying
Slow to roast; beans tend to be yellowish; loss of acidity; harsh; ashy flavour
F/P
Black-green bean* Unripe coffee bean often with a wrinkled surface, with dark-green (dark-dark-green bean) to black-green silverskin colour
High temperatures affecting immature beans, causing chemical transformation (like fermentation) with the silverskin becoming dark or black-green
Slow roast; rotten fish flavour
H/P
Light-green immature bean*
Unripe coffee bean often with a wrinkled surface. The bean has a greenish or metallic-green silverskin colour. Cell walls and internal structure are not fully developed
Beans from cherries picked before ripening Slow roast;
bitterness; less acidity; range of colours: light to dark brown-reddish, dark brown or yellowish green internally (endosperm). In some cases it has a waxy appearance or a brown silverskin colour
Bean from immature, mature or overripe cherries that have been in adverse conditions, becoming fermented by bacteria or xerophilic moulds, with embryo death. More frequent in fruits fallen to the ground, can also appear in fruits on the tree, and when there is an excessive time between harvesting and drying or pulping
Sour; fermented; acetic;
fruity; sulphurous; vinegar flavour
F/H/P
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Withered bean* Coffee bean wrinkled and light in weight
Underdeveloped fruit due to genetic and physiological problems, nutritional lack, drought or heavily stressed tree
Slight loss of acidity F
Spongy bean* Coffee bean of consistency like cork that may be verified by pressure of fingernail. Whitish in colour
Moisture absorption during storage or transportation leading to deterioration by enzymatic activity
Roasts rapidly; lack of acidity; woody
S
Whitish bean* Coffee bean with whitish colour with tissue of normal density
Discoloration of surface due to bacteria of the genus Coccus, during storage or transportation. Associated with old crop. Faulty drying of the bean
Woody; stale; bitterness taste
P/S
Mouldy bean* Coffee bean with mould growth and evidence of attack by mould visible to the naked eye
Temperature and humidity conditions favourable to mould growth
Musty flavour P/S
Frost-damaged bean*
Coffee bean with spotted silverskin like a ‘spotted quail egg’
Frost damaged coffee bean Rancid flavour F
*Found in WPA/WPR/DPA/DPR.
Abbreviations: WPA, wet-processed arabica; WPR, wet-processed robusta; DPA, dry-processed arabica; DPR, Dry-processed robusta.
F, Field damaged bean: defects originating in the field, the coffee tree (genetic problems), the environment (climate, soil, water and nutrient stress), attacks by pests and diseases.
H, Harvest-damaged beans: inadequate crop management (picking cherries before or after maturation, cherries from the ground, etc.).
P, Process-damaged beans: defects due to imperfect processing operations (pulping, washing, drying, cleaning, hulling, etc.).
S, Storage damaged beans: defects due to deficient storage (faulty storage practices and storage pests).
EspressoCoffee Table 3.8 Defects associated with beans irregular in cup taste after proper roasting and brewing (off-taste coffee)
Name Characteristics/definition Causes
The bean presents a normal appearance.
Unpleasant foul flavour is detected in the cup like earthy, woody, musty or jute-bag
Unfavourable conditions of temperature, humidity and time in processing, storage or transportation. Use of bad quality jute-bag
The bean presents usually a normal appearance. A very unpleasant flavour is detected in the cup like stinker, over-fermented or rotten. Stinker smell when cut or scratched
Delay in pulping; too long period of fermentation;
wild fermentation in beans trapped in the pulping machines or tanks. Abrasion of beans during pulping, losing the superficial protective layer, leaving them susceptible to microorganism attack. Contamination with recycled polluted water
The bean presents a normal appearance. Medicinal smell when cut or scratched.
Overripe cherry left on branch, possibly contaminated by microorganisms. The drying patio soil is heavily contaminated by microorganisms and/or TCA (trichloroanisole)
Abbreviations: WPA, wet-processed arabica; WPR, wet-processed robusta; DPA, dry-processed arabica; DPR, dry-processed robusta.
F, Field-damaged bean: defects originating in the field, the coffee tree (genetic problems), the environment (climate, soil, water and nutrient stress), attacks by pests and diseases.
H, Harvest-damaged beans: inadequate crop management (picking cherries before or after maturation, cherries from the ground, etc.).
P, Process-damaged beans: defects due to imperfect processing operations (pulping, washing, drying, cleaning, hulling, etc.).
S, Storage-damaged beans: defects due to deficient storage (faulty storage practices and storage pests).
defects are characteristic of a certain type of processing. The different types of defects can be divided into categories, which are discussed below.
3.7.1.1 Defects associated with foreign matter
These include defects such as stones, sticks, clods (agglomerations of earth), metal and foreign matter. They must be removed at an appropriate stage, for example during the cleaning of green coffee, by sieving, classifying or by removal of metals.
3.7.1.2 Defects associated with coffee fruit parts
These include defects such as beans in parchment, pieces of parchment, husk fragments and dried cherries (pods). In general, these are removed by sieving or by air classifying, leading to a loss of physical volume.
3.7.1.3 Defects associated with regularity/integrity of bean shape
These include defects like malformed beans (shell/ear and shell core/body of the elephant), bean fragments, broken beans, insect-damaged beans, pulper-nipped/pulper-cut beans and crushed beans. They are in general removed by densimetric sorting and in some cases by optical sorting.
3.7.1.4 Defects associated with beans irregular in visual appearance (colour and surface texture)
These include defects like black beans, dark- and black-green immature beans, light-green immature beans, sour beans etc. Some of these can be removed by hand or by optical sorting techniques.
3.7.1.5 Defects associated with beans irregular in cup taste after proper roasting and brewing (off-taste coffee) Defects of sensory concern, to be identified after sample roasting and cup testing, also entailing a further risk of contamination of other beans. These include defects like ‘stinker’ beans, foul/dirty beans and ‘rio’ beans. Off-tastes are hard to remove by sorting. They can be identified after cupping a sample of roast and ground coffee, following proper roasting and brewing.
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