glossary: green coffee

ANAEROBIC FERMENTATION

A type of coffee processing that usually refers to a sealed tank fermentation for depulped parchment. After depulping, the coffee is fermented either in clean water or the water used to depulp it, in an airtight tank to prevent new oxygen introduction, with a one-way valve for off-gassing. Technically speaking, all fermentation is by nature anaerobic. In coffee, fermentation occurs alongside aerobic maceration, thus the term anaerobic fermentation is usually applied to the sealed-tank style of processing which can limit the microbial population and activity.

BRIX

A method of measuring the sugar content of a solution, often employed in winemaking. Can be (sometimes controversially) used in coffee to determine cherry ripeness or degree of fermentation. Usually measured with a specific refractometer.

CARBONIC MACERATION

Similar to anaerobic fermentation, this is processing method involving a sealed tank fermentation step. However, carbonic maceration usually refers to whole cherry fermentation, instead of depulped parchment. Coffee cherries are often added to a large tank filled with clean water. The tank is sealed with a one-way valve for off-gassing of released carbon dioxide, and the environment allows no new oxygen in. The fermented coffee must be depupled after this step before drying.

CHERRY FLOATION

The pre-processing step responsible for cleaning the whole cherry before depulping, fermenting, and/or drying. Also functions to separate floaters – lower quality, low density fruits – from the sinkers, which are of higher density and quality. Sometimes referred to as “Triple Washed” or “Burundi Process.

CHERRY HULL/HUSK

Pieces of dried parchment or cherry skin can be left on the coffee bean or included loose with the packed beans due to poorly calibrated hulling/depulping equipment and insufficient sorting. May increase the risk of a fire during roasting.

COFFEE BEAN

The seed of the coffee fruit. Two seeds are found inside most coffee cherries, and this is what we roast.

CULTIVAR

A variety of coffee that has been deliberately cultivated by selective breeding. These will not usually produce true to type offspring; rather, they are often hybrids or selected mutations and must be propagated with human intervention.

DEMUCILAGE

Partial or complete removal of the coffee’s mucilage down to the parchment. Fermentation is used to demucilage coffee. Alternatively, coffee’s mucilage may be removed with specialized equipment capable of removing more of the coffee fruit compared to a traditional depulper.

DENISTY

A measurement of the amount of coffee that can fit in a given 3-dimensional space, mathematically expressed as mass divided by volume.

DEPULPING

The removal of fruit layers from the parchment coffee. There are a wide variety of machines able to depulp coffee, from manual to mechanical and eco-friendly.

DROUGHT DAMAGE

Under drought conditions, green coffee beans can become withered/wrinkled and/or have a lower density, and can negatively affect sensory quality.

DRY MILL

The location responsible for hulling parchment, sorting for defects, density, and screen size, and bagging for export.

EUROPEAN PREP (EP)

Central American coffees may use the term EP to indicate screen size (15-18), in addition to SHB or SHG to refer to the highest grade of coffee based solely on elevation.

FERMENTATION

A metabolic process that produces chemical changes in organic substances through the actions of enzymes. In coffee, it refers to leaving the harvested beans (whether washed or in cherry) to rest and allow microorganisms, usually yeast and bacteria, to macerate the coffee fruit, which has a significant impact on final flavor profile. In washed coffees, this fermentation is used to demucilage parchment before drying.

FLOATER

A low density, secondary defect, sometimes an immature seed, which can negatively affect cup quality. Floaters may be sorted by cherry flotation and/or by channel during washed coffees processing.

HANDPICKING

The traditional practice of harvesting coffee cherries using manual labor. Attentive workers may pick only ripe cherries, which can improve the sensory quality of the final product (though this is time consuming and labor intensive compared to mechanical picking). Pickers may also strip pick the cherries, pulling them all (ripe and unripe) at once from the branch.

HEIRLOOM

Broadly used to refer to any variety that has not crossed with another. More strictly, plant breeders and gardeners use “heirloom” to refer to non-commercial fruits and vegetables. In the 1940s and 50s, commercial breeds became increasingly important in global agriculture. Thus, an heirloom plant is often a private, home-garden reaction against this type of farming. In coffee, it is often (and somewhat controversially) applied to Ethiopian forest varieties, and more broadly to global legacy varieties like Typica and Bourbon.

HONEY PROCESS

A coffee processing method in which coffee cherry skins are removed and then dried without removing the mucilage. Also called “pulped-natural” or “semi-washed.

HULLING

Removing the parchment and/or dried cherry skin from the seed prior to sorting and export. Takes place at the Dry Mill.

HYBRID

Refers to a unique plant bred from two distinct genetic parents. Naturally occurring hybrids are not rare for coffee, since cross-pollination occurs readily with other nearby trees. Hybrids created in labs are commonly bred for disease resistance or improved yield, for example. Because hybrids contain unique genetic material contributed from two separate populations, they are said to have “hybrid vigor,” or increased genetic diversity. By selecting a particular accession for a unique genetic trait, a hybrid can be crafted to retain desirable characteristics of its parents and propagate new cultivars

IN-CHERRY

Fermentation of the whole fruit. While de facto in-cherry fermentation occurs during the natural process, it can also be employed in controlled environments, such as a sealed tank or covered raised bed.

INTRASPECIFIC

Refers to hybrids bred from parents of the same species. Mundo Novo is a spontaneous intraspecific hybrid of two traditional arabica varieties, for example.

INTERSPECIFIC/INTROGRESSED

Hybrids that are a cross of different species. The Timor Hybrid is an interspecific hybrid of Coffea arabica and robusta (C. canephora). Interspecific hybrids can also be referred to as introgressed, meaning new genetic material was introduced.

JUTE

A type of plant fiber used to make the bags used to hold and transport coffee and many other products. Synthetic and natural alternatives exist, but jute remains the most common option. Sizes vary but the most common for coffee are 60, 69, and 70 kilos.

LANDRACE

A wild variety, like those found in coffee forests across Ethiopia. Landraces are generally considered domesticated, but locally adapted, and distinct from any formal breeding or selection. Thus both a wild forest coffee and a traditional home garden in Ethiopia could be growing a landrace variety.

LINER

A bag for holding coffee placed inside the jute, intended to preserve the integrity of green coffee by preventing moisture damage and oxidation. Common brands include EcoTact, Grainpro, Vidaplast, and AZ bags.

MACHINE HARVESTING

The act of picking coffee cherries using a machine. Mechanical harvesters function by straddling the trees, driving over them and oscillating at high speeds, causing coffee cherries to fall onto collection plates or the ground. Can only be accomplished on relatively flat terrain, most commonly in Brazil’s macro farming regions of Mogiana and Minas Gerais.

MOISTURE CONTENT

The quantity of water contained in the coffee bean, commonly measured as percentage of mass.

MUCILAGE / PULP

The flesh of the coffee cherry, directly beneath the skin. This layer surrounds the coffee seeds with a sticky, sugary substance.

NATURAL

Also called “dry-process” or “fruit- or cherry-dried.” A coffee processing method of letting the coffee fruits dry with the skin and mucilage intact, which are removed later at a dry mill. Tends to produce the fruitiest tasting coffees.

PARCHMEN

The layer of cellulose beneath the mucilage that protects the coffee bean and resembles parchment paper when dried. Parchment may be hand-hulled for samples, but is removed commercially by machines at the dry mill.

PARCHMENT DEFECT

A hulling error where some beans are found still fully or partially covered in parchment due to poorly calibrated dry mill equipment. It can negatively impact flavor and increase the risk of fire during roasting.

PEABERRY

A coffee cherry which underwent a genetic mutation to produce only one seed instead of two. Peaberries are smaller and rounder than coffee beans that develop in pairs. About 5% of an average harvest might be peaberry beans.

POST-FERMENTATION SOAK

A secondary tank used to hold coffee parchment in clean water immediately after depulping, fermenting, and washing. Fermentation continues but at a much slower pace due to the reduced microbial load in the slurry. Sometimes called “double washed” or “Kenya process.”

POST-HARVEST PROCESSING

All the aspects of coffee preparation that occur after harvest. Post-harvest processing covers everything at the wet mill and dry mill, from depulping, fermentation, drying, hulling, sorting, and bagging for export

PRIMARY DEFECT

A classification of green coffee defect according to the SCA and CQI. Coffee must show no primary defects in order to be classified as specialty grade green coffee. Primary defects are considered to have the greatest impact on cup quality, and include full black, full sour, foreign matter, dried cherry/pod, fungus damage, severe insect damage, and foreign matter.

PROCESSING DEFECT

Defects that occur during preparation of coffee at the wet mill or dry mill. These are generally the most commonly encountered defects, which are usually the result of some combination of human and mechanical errors.

QUAKER

A coffee seed that does not properly brown during the Maillard stage of roasting, appearing much paler in comparison to its counterparts. Quakers are only identifiable once the coffee has been roasted, and are sometimes associated with immature coffee.

SAMPLE ROASTER

Small, often multi-barrel machines intended to produce enough roasted coffee to cup once or twice for quality evaluation (a common batch size be 100 grams), often in order to make purchasing decisions or for a quality control check on green coffee as it ages in storage, for example. (See also: sample roast.)

SIGHTGLASS

A window into the roasting chamber, used for visual assessment of the color of the roasted coffee or to observe the rate of drum revolution.

STACK

Large, hollow, central column through which non-combustible/microscopic particulates and/or smoke travel from the roaster and exit the building. Chimneys positioned directly above the roaster using a straight vertical stack provide fewer opportunities than angled stacks to accumulate creosote and other impurities, which may clog columns over time and increase the risk of fires.

STIRRING ARMS / AGITATORS

Fins/paddles attached to a moving gear that stirs coffee in the cooling tray to help it spread, and thus cool evenly after roasting.

SCREEN SIZE

Screen size traditionally has been measured by passing coffee through circular holes. These holes are typically measured in increments of 1/64 of an inch in diameter, so a coffee measuring screen size 16 means the coffee is 16/64” – or a quarter of an inch – across. Most screen size measurement fall between 12 and 20.

SECONDARY DEFECT

A less severe classification of green coffee defect according to the SCA and CQI. Specialty coffee may show a varying number of secondary defects, depending on which defect, in order to be classified as specialty grade green coffee.

SELECTION

Systematic and intentional botanical choices, which are reproduced for distribution. In other words, the process by which a landrace and/or natural variation in a field or offspring in a breeding program are chosen for further breeding, cloning, or wider dissemination. Ex: Gesha was selected from a limited number of seeds from a wild population in Western Ethiopia.

SHELLS

A developmental anomaly caused by false polyembryony. The coffee bean develops into two separate halves, one tucked inside the other, which come apart easily and may roast unevenly.

SILVER SKIN (PERISPERM)

A thin, semi-translucent peel that wraps the coffee seed. Usually grey-green in color (though it may take on reddish hues if ripened or dried in the fruit). During the roasting process this silver skin dries and falls off, becoming chaff.

SKIN (EXOCARP)

The outer skin of coffee cherry that covers the fruit.

SOUR (FULL OR PARTIAL)

A defect that may be caused by too long a wait between picking and depulping, an overly long fermentation process, or storing the coffee beans while they have too high a moisture content. Full sour is a primary defect, while partial sour is a secondary defect.

SPOT

Coffee that is located domestically, usually in a warehouse and available for purchase.