Every key term, variety, process, and concept used across The Coffee Guide — defined clearly and simply in this Glossary. Use the jump menu to navigate by letter, or scroll through to explore.
A – B – C – D – E – F – G – H – I – J – K – L – M – N – O – P – Q – R – S – T – U – V – W – X – Y – Z
A
Arabica Species
Coffea arabica — the most widely grown and highly regarded coffee species in the world, accounting for around 60% of global production.
Arabica plants require cool, high-altitude conditions (typically 1,000–2,000m), produce lower yields than Robusta, and are more susceptible to disease.
In return, they offer greater flavour complexity, brighter acidity, and lower caffeine content.
Almost every origin in the specialty coffee world is Arabica-focused.
Acidity Tasting
In coffee, acidity doesn’t mean sourness — it refers to a bright, lively quality in the cup that adds complexity and lift.
Good acidity feels clean and pleasant; it can be citrusy (like Kenya), winey (like Tanzania), or apple-like (like Colombia and Peru).
Low-acidity coffees (Brazil, Vietnam, India) feel smoother and heavier but less vibrant.
AeroPress Brewing
A versatile, pressure-based coffee brewer invented in 2005. Coffee grounds steep in a chamber before being pushed through a paper or metal filter by manual air pressure. Produces a clean, concentrated cup with full control over brew time, temperature, and pressure. Particularly well suited to Thai, Nicaraguan, and Colombian coffees.
Andean Cordilleras
The Andean Cordilleras are the mountain ranges that form part of the Andes, stretching through countries such as Colombia, Ecuador and Peru. Their high elevations, volcanic soils and favourable climates create ideal conditions for growing high-quality Arabica coffee. The combination of cool temperatures and slow cherry maturation helps produce beans with greater sweetness, complexity and vibrant acidity, making the Andean Cordilleras one of the world’s premier coffee-growing regions.
Agitation
Agitation is the movement of water through and around the coffee grounds during brewing. It can be created by pouring, stirring, swirling, or gently shaking the brewer. Agitation helps ensure that fresh water comes into contact with all of the coffee particles, promoting a more even extraction.
The amount of agitation affects flavour. Too little agitation may result in uneven extraction and sour or weak coffee, while excessive agitation can increase the extraction of bitter compounds and fine particles, producing a harsher cup. Controlled agitation is an important variable in pour-over, immersion, and espresso brewing.
See also: Extraction, Pulse Pour, Continuous Pour, Bloom.
B
Baba Budan History
A 17th-century Sufi pilgrim from India’s Mysore region, credited with smuggling seven fertile coffee seeds out of Yemen taped to his stomach — breaking the Arab monopoly on coffee cultivation. He planted them in the hills of Karnataka, India, in what is now the Baba Budan Giri region, still producing coffee today.
Black honey Processing
The most intensive level of honey processing, in which maximum mucilage is left on the bean during drying. Produces the most complex, fruit-forward, and wine-like cup of all honey process variants. Pioneered in Costa Rica and now practised widely in Thailand and other specialty origins.
Bloom Brewing
The first small pour of hot water over ground coffee at the start of a pour-over or filter brew. Fresh coffee releases CO₂ gas when it contacts hot water — the bloom allows this gas to escape before the main brew, preventing uneven extraction. Typically 30–45 seconds with roughly twice the weight of water to coffee.
Bourbon Variety
One of the oldest and most celebrated Arabica varieties, originating on the island of Réunion (formerly Bourbon). Known for a rounded sweetness and layered complexity. Widely grown in Guatemala, Colombia, and across Central America. A natural mutation of Typica and the ancestor of many modern cultivars including Caturra.
C
Casein
Casein is the primary protein found in milk, accounting for approximately 80% of its total protein content. It exists as tiny spherical structures called casein micelles, which remain evenly suspended in milk and contribute to its smooth texture, white appearance, and ability to foam.
In coffee preparation, casein plays an important role in the texture and stability of steamed milk. During steaming, the casein proteins help stabilise the microscopic air bubbles created by the steam wand, producing the fine, velvety microfoam required for drinks such as cappuccinos, flat whites, and lattes. Casein also binds with naturally occurring compounds in coffee, helping to soften bitterness and reduce perceived acidity, resulting in a smoother, creamier flavour.
The balance of casein and milk fat is one of the reasons whole milk is often preferred for milk-based espresso drinks, although modern barista-formulated plant-based alternatives are designed to mimic many of casein’s foaming and stabilising properties.
Catimor Variety
A hybrid variety bred from Timor (a natural Arabica–Robusta cross) and Caturra. Disease-resistant and high-yielding, making it practical for farmers in humid, lower-altitude regions. The dominant variety in Yunnan, China, and widely grown in Vietnam and Southeast Asia. Can produce flat or earthy profiles at low altitude but shows genuine complexity when grown high and processed well.
Catuai Variety
A hybrid of Caturra and Mundo Novo, developed in Brazil. Compact, high-yielding, and resistant to wind and rain damage. One of the most widely planted varieties in Costa Rica, Honduras, and Brazil. Produces a clean, balanced cup — workmanlike rather than spectacular, but exceptionally reliable.
Caturra Variety
A natural mutation of Bourbon, first discovered in Brazil. Compact and productive, making it suitable for dense planting on steep mountain slopes. Widely grown across Central and South America. Produces a bright, clean cup with good acidity — one of Colombia’s and Costa Rica’s most important varieties.
Chemex Brewing
An hourglass-shaped pour-over brewer, designed in 1941, that uses a heavy-bonded paper filter significantly thicker than standard V60 or drip filters. This removes virtually all oils and sediment, producing an exceptionally clean, clear cup. Ideal for bright, complex origins like Kenya, China’s Yunnan, and Colombia where maximum clarity is desired.
Coffee cherry Plant
The fruit of the coffee plant. A mature coffee cherry is typically red or yellow, roughly the size of a grape, and contains two coffee seeds (beans) inside. The cherry consists of the outer skin, a layer of sweet fruit pulp, a sticky mucilage layer, a protective parchment, and the green coffee bean itself.
Cold brew Brewing
Coffee brewed by steeping coarsely ground coffee in cold water for an extended period — typically 14–18 hours in the refrigerator. The low-temperature extraction produces a smooth, naturally sweet concentrate with very low perceived bitterness. Particularly well suited to Nicaragua, Thailand, and Brazil.
Cordillera Geography
A chain or ridge of mountains running in a roughly parallel line — from the Spanish word “cuerda” meaning cord or rope. In Colombia, the single Andes mountain range splits into three distinct parallel cordilleras as it enters the country from the south: the Western, Central, and Eastern Cordilleras. Each has its own altitude profile, climate, and soil type, creating the dozens of microclimates that make Colombia capable of year-round harvesting and exceptional flavour diversity.
Crema Espresso
The tan, foam-like layer that forms on the surface of a well-pulled espresso shot, created when pressurised hot water emulsifies the coffee’s natural oils and CO₂. A thick, persistent crema is generally a sign of fresh, well-roasted coffee and good extraction. Robusta-heavy coffees (India, Côte d’Ivoire, Uganda) produce particularly abundant crema due to their higher oil and caffeine content.
Continuous Pour
A continuous pour is a pour-over brewing technique in which water is added in one steady, uninterrupted stream after the bloom phase, maintaining a relatively constant water level throughout the brew. Unlike pulse pouring, the kettle is not stopped between additions.
Continuous pouring creates a more stable flow through the coffee bed and generally produces less agitation than multiple pulse pours. When performed with a consistent flow rate and controlled kettle movement, it can improve extraction uniformity and often results in a cleaner, more balanced cup.
See also: Pulse Pour, Agitation, Bloom, Pour-Over Brewing.
D
Doi Moi History
Vietnam’s sweeping economic reform programme introduced in 1986, which transformed the country from a centralised command economy to a market-oriented system. The decentralisation of land rights and market access under Doi Moi triggered an explosion in smallholder coffee farming, propelling Vietnam from a minor coffee producer to the world’s second largest within two decades.
Double fermentation Processing
An advanced processing technique pioneered in Yunnan, China, in which coffee undergoes two separate fermentation stages — the first using naturally occurring yeasts, the second using introduced cultured yeast strains, sometimes derived from tea fermentation cultures. Produces elevated levels of aromatic complexity, fruity character, and a wine-like depth unusual in Asian coffee.
DRUGAR Processing
Dry Ugandan Arabica — the naturally processed grade of Ugandan specialty Arabica, grown primarily on the slopes of Mount Elgon. Natural processing leaves the whole cherry intact during drying, producing a fuller-bodied, fruitier cup with more of Uganda’s characteristic dark berry intensity. Compare with WUGAR (washed).
E
Elephant bean Variety
A nickname for the Maragogype and Liberica varieties, both of which produce unusually large beans — sometimes two to three times the size of a standard Arabica. The Malaysian Liberica and Nicaraguan Maragogype are the two most commonly encountered “elephant beans” in specialty coffee.
Espresso Brewing
A concentrated coffee brewing method in which hot water is forced through finely ground coffee under 9 bars of pressure, producing a small, intense shot with a layer of crema on top. The foundation of most café-style drinks (flat white, latte, cappuccino). Particularly well suited to low-acidity, high-body origins like Brazil, India, and Guatemala.
Extraction
Extraction is the process of dissolving flavour compounds from roasted coffee into water during brewing. As hot water passes through or surrounds the coffee grounds, it dissolves acids, sugars, aromatic oils, and other soluble compounds that together create the flavour, aroma, and body of the finished cup.
The degree of extraction has a major influence on taste. Under-extraction typically produces coffee that is sour, sharp, and lacking sweetness, while over-extraction can result in bitterness, dryness, and astringency. Achieving a balanced extraction depends on factors such as grind size, water temperature, brew time, coffee-to-water ratio, agitation, and brewing method.
See also: Extraction Yield, Under-Extraction, Over-Extraction, Agitation, Brew Ratio.
Extraction Yield
Extraction yield is the percentage of a coffee’s soluble material that is dissolved into the brewing water during extraction. It is calculated by comparing the amount of dissolved coffee solids in the finished beverage with the original weight of the dry coffee used to prepare it.
For most brewed coffee, an extraction yield between 18% and 22% is generally considered the ideal range for achieving a balanced cup, although the preferred level may vary depending on the coffee, roast profile, and brewing method. Extraction yield is commonly measured using a refractometer in conjunction with Total Dissolved Solids (TDS). While it is a useful tool for evaluating brewing performance, flavour should always remain the final measure of a successful extraction.
See also: Extraction, Total Dissolved Solids (TDS), Under-Extraction, Over-Extraction.
F
F1 hybrid Variety
A first-generation hybrid variety produced by crossing two genetically distinct parent plants. In coffee, F1 hybrids are being developed specifically to combine the cup quality of traditional Arabica varieties with resistance to climate change, leaf rust, and other threats. Costa Rica is one of the leading testing grounds for F1 coffee hybrids.
Fair Trade Certification
An international certification system that guarantees farmers a minimum price for their coffee regardless of market fluctuations, along with social and environmental standards. Mexico and Peru are among the world’s leading Fair Trade coffee exporters, largely because their smallholder cooperative structures align naturally with Fair Trade’s community-based model.
Flash chilling Brewing
A method of making iced coffee by brewing hot coffee directly over a glass full of ice, chilling it instantly rather than cooling it gradually. The rapid temperature drop locks in volatile aromatic compounds, producing a bright, vivid iced cup. Particularly effective with fruit-forward origins like Costa Rica and Colombia. Brew at double strength (1:8 ratio) to compensate for ice dilution.
French press Brewing
An immersion brewing method in which coarsely ground coffee steeps in hot water before a metal mesh plunger is pressed to separate grounds from liquid. The metal filter allows natural oils and fine sediment to pass into the cup, producing a fuller, heavier body than paper-filtered methods. Ideal for Indonesian, Malaysian, and Ugandan coffees where body and oils are desirable.
G
Garden coffee Production
Coffee grown on small family plots — often called shamba in East Africa — rather than large commercial estates or industrial plantations. Ethiopia is the definitive garden coffee producer, with most beans grown on plots of less than two hectares by smallholder families using traditional, low-intervention methods passed down through generations.
Giling Basah Processing
Indonesian for “wet grinding” — a unique processing method practised almost exclusively in Indonesia (particularly Sumatra) in which the coffee parchment is removed while the bean is still unusually high in moisture (30–35%), rather than after full drying. Exposure of the bare, damp bean to the humid tropical air during final drying triggers a chemical reaction that dramatically lowers acidity and builds a heavy, syrupy body with intense cedar, tobacco, and dark chocolate notes.
Golden Triangle History
The mountainous border region where Thailand, Myanmar, and Laos converge — historically one of the world’s largest opium-producing areas. The transformation of this region’s hill tribe communities from poppy cultivation to coffee farming was the central aim of Thailand’s Royal Project, initiated by King Bhumibol Adulyadej in 1969.
H
Heirloom varieties Variety
A term used in Ethiopian coffee to describe the vast, largely undocumented genetic diversity of indigenous wild and semi-wild Arabica plants that have evolved naturally in Ethiopia’s forests over millennia without human selection. Unlike cultivated varieties grown elsewhere, Ethiopian heirlooms represent thousands of distinct genetic expressions — giving Ethiopian coffee a flavour complexity that no other origin can fully replicate.
Honey process Processing
A coffee processing method that sits between washed (fully fruit-removed) and natural (whole cherry dried intact). After depulping, a controlled amount of the sticky mucilage layer is left on the bean during drying. The amount retained determines the “colour” — yellow honey (least mucilage), red honey (medium), black honey (maximum). Pioneered in Costa Rica; also widely practised in Thailand. Produces a cup sweeter than washed but cleaner than natural, with characteristic stone fruit and caramel notes. The “honey” refers to the sticky texture of the mucilage, not to the taste.
I
IHCAFÉ Institution
Instituto Hondureño del Café — the Honduran Coffee Institute, the national body responsible for quality certification, grading, and promotion of Honduran coffee internationally. IHCAFÉ played a central role in Honduras’s transformation from an anonymous bulk producer to a recognised specialty origin in the early 2000s.
J
Java History
An Indonesian island and one of the first places outside Ethiopia and Arabia to grow coffee at commercial scale, established by the Dutch East India Company in 1696. Java’s dominance of the early global coffee trade was so total that its name became — and remains — everyday English slang for coffee itself.
Juan Valdez History
A fictional Colombian coffee farmer — depicted with his mule Conchita — created in 1958 by the Federación Nacional de Cafeteros as the face of Colombian coffee marketing. One of the most successful agricultural branding campaigns in history, Juan Valdez made “100% Colombian” synonymous globally with hand-picked, premium-quality coffee and remains an active brand today.
K
Kaapi Royale Grade
A premium grade of Indian Robusta grown at high altitude in the Wayanad region of Kerala. Unlike standard Robusta, Kaapi Royale carries far less of the harsh bitterness associated with the species, offering instead a dense chocolate body and outstanding crema production. One of the most sought-after Robustas in the world for espresso blending.
Kaldi History
A legendary 9th-century Ethiopian goat herder credited in folklore with discovering coffee after noticing his flock became energetic after eating red berries from a wild shrub. Almost certainly not literally true, but the legend points to a genuine reality — coffee does originate in Ethiopia, where it grew wild in the forests for millennia before humans began cultivating it.
Kapeng Barako
Kapeng Barako is a traditional coffee grown primarily in the provinces of Batangas and Cavite in the Philippines. The name combines the Tagalog word kapeng (“coffee”) with barako, meaning “strong”, “brave”, or “wild boar”—a reference to the coffee’s bold character and robust flavour.
Kapeng Barako is produced from Coffea liberica, one of the four commercially cultivated coffee species. Liberica accounts for only a small percentage of global coffee production but is renowned for its large cherries, oversized beans, and distinctive flavour profile. Unlike the more common Arabica and Robusta, Kapeng Barako is celebrated for its full body, low acidity, and intense aroma, with tasting notes that may include dark chocolate, roasted nuts, spice, jackfruit, tobacco, and hints of smoky wood.
Introduced to the Philippines during the nineteenth century, Liberica became especially important after coffee leaf rust devastated many Arabica plantations throughout the world. Its natural resistance to disease and ability to thrive in the country’s tropical climate helped establish Kapeng Barako as a symbol of Philippine coffee culture.
Today, Kapeng Barako remains a prized regional speciality and has experienced renewed interest among specialty coffee producers seeking to preserve its unique heritage and distinctive flavour.
Kenya AA Grading
The top grade in Kenya’s rigorous bean-size grading system, denoting beans with a screen size of 18 or above — the largest, densest Kenyan beans. Kenya AA is the grade most associated with the country’s specialty reputation and commands the highest prices at the Nairobi Coffee Exchange auction.
Kopitiam Culture
A traditional Malaysian coffee shop — found on virtually every street corner in Malaysian towns and cities — serving Liberica-based Kopi-O alongside kaya toast and soft-boiled eggs. The kopitiam is a continuous cultural institution that has run largely unchanged since the late 19th century, when Malaysia’s shift to Liberica coffee following the leaf rust crisis created its own distinct café culture.
Kopi-O Culture
Traditional Malaysian black coffee, made from Liberica beans roasted with margarine and sugar — a process that caramelises the bean surface and produces a dark, glossy, intensely flavoured roast. Brewed through a cloth “sock” filter and typically served strong and sweet. The defining beverage of the Malaysian kopitiam.
L
Lactic acid Science
An organic acid produced during certain fermentation processes. In Thai honey process coffee, the mucilage’s high sugar content triggers lactic acid fermentation, producing elevated lactic acid levels in the finished bean. This compound is directly responsible for the creamy, smooth mouthfeel that characterises well-made Thai specialty coffee.
Lempira Variety
A Honduran coffee variety developed specifically for the country’s cloud forest growing conditions, named after the 16th-century indigenous leader who resisted Spanish conquest. One of Honduras’s most widely planted specialty varieties, producing a clean, sweet cup that performs consistently at high altitude.
Liberica Species
Coffea liberica — the third major coffee species after Arabica and Robusta, accounting for less than 1% of global production. Liberica trees can grow up to 20 metres tall and produce large, distinctively hooked “elephant beans.” The flavour is intensely polarising — described variously as jackfruit, smoky chorizo, and dark chocolate. Malaysia is the only country to grow Liberica commercially at meaningful scale.
LQIP Technical
Low Quality Image Placeholder — a tiny, blurry version of an image embedded in a webpage’s HTML as a base64 string, shown while the full-resolution image loads. Used in lazy loading systems to prevent blank spaces during page load. When oversized or improperly configured, LQIP can significantly increase page weight and slow mobile load times.
M
Maillard Reaction
The Maillard reaction is a complex series of chemical reactions that occur when amino acids and natural sugars in coffee beans are heated during roasting. Named after the French chemist Louis-Camille Maillard, who first described the process in 1912, it is responsible for developing many of the rich aromas, flavours, and brown colour associated with roasted coffee.
In coffee roasting, the Maillard reaction begins after the beans have lost much of their moisture, typically at temperatures above 140°C, and continues until the onset of First Crack. During this stage, hundreds of new flavour and aroma compounds are created, transforming the grassy, vegetal characteristics of green coffee into notes of caramel, toasted nuts, chocolate, malt, biscuit, and roasted grain.
The length and intensity of the Maillard phase have a significant influence on the final cup profile. A longer Maillard stage generally promotes greater sweetness, body, and complexity, while a shorter phase may preserve brighter acidity and floral characteristics. Roasters carefully manage this stage to achieve the desired balance between sweetness, acidity, and mouthfeel.
Although often associated with caramelisation, the Maillard reaction is a separate process. Caramelisation involves the breakdown of sugars alone at higher temperatures, whereas the Maillard reaction requires both sugars and amino acids to produce its distinctive flavour compounds.
Maragogype Variety
A natural genetic mutation of the Typica variety, first discovered in the Brazilian municipality of Maragogipe. Produces some of the largest coffee beans in the world — sometimes two to three times the size of standard Arabica — earning it the nickname “elephant bean.” Nicaragua is the world’s leading Maragogype producer. The beans are porous and low-density relative to their size, requiring careful roasting, but produce a cup of unusual clarity and silky body when handled well.
Micro-mill Production
A small-scale coffee processing facility owned and operated by an individual farmer or small cooperative, rather than a large centralised industrial mill. The Micro-Mill Revolution — which began in Costa Rica in the early 2000s — gave smallholder farmers direct control over fermentation, mucilage levels, and drying conditions for the first time, enabling a level of processing precision and experimentation that transformed the country’s specialty coffee output.
Moka pot Brewing
A stovetop coffee brewer, invented in Italy in 1933, that uses steam pressure to force hot water up through ground coffee into an upper chamber. Produces a concentrated, oil-rich brew with moderate pressure — not true espresso, but significantly stronger and more intense than filter coffee. Particularly well suited to Indian, Indonesian, and Ugandan coffees.
Monsooned Malabar Processing
A uniquely Indian coffee processing method in which green beans are stored in open-sided warehouses on the Malabar Coast during the monsoon season (June–September), exposing them to the moist winds blowing in from the Arabian Sea. Over 12–16 weeks the beans swell, turn pale gold, and lose most of their natural acidity — replicating the transformation that Indian coffee underwent during centuries of sea voyages to European markets. The result is a thick, low-acid cup with a distinctive “musty” sweetness and spicy depth.
Mucilage Plant
The sticky, sugar-rich layer of fruit pulp that surrounds the coffee bean inside the cherry, sitting between the outer fruit flesh and the inner parchment. Rich in sucrose and fructose, mucilage plays a central role in honey processing (where it is deliberately retained during drying) and fermentation (where its sugars fuel microbial activity that shapes the cup’s flavour).
N
Natural processing Processing
Also called dry processing — a method in which harvested coffee cherries are dried whole, with the skin and fruit still intact around the bean. The fruit slowly ferments and dries over several weeks, infusing the bean with sugars and creating a heavier body, fruity sweetness, and wine-like complexity. Used extensively in Brazil, Ethiopia (Harrar), and increasingly in experimental specialty processing worldwide.
Nairobi Coffee Exchange Institution
Kenya’s centralised coffee auction system, through which virtually all Kenyan coffee is traded. International buyers bid competitively for individual lots, with the highest-quality beans (Kenya AA) attracting the highest prices. The auction incentivises quality at every stage of production and has been central to Kenya’s reputation as the world’s most technically sophisticated coffee origin.
O
Old Brown Java History
A legendary historical coffee profile associated with Indonesian (particularly Javanese) coffee that spent months at sea in wooden ship hulls en route to European markets. The salt air and humidity of the voyage transformed the green beans — turning them brown, swelling them, and mellowing their acidity — creating a thick, mellow cup prized above all others by 17th-century European coffee drinkers. The Giling Basah (wet-hulled) process was developed to recreate this profile on land.
Organic certification Certification
Third-party verification that coffee has been grown without synthetic fertilisers, pesticides, or herbicides. Peru and Mexico are the world’s leading exporters of certified organic coffee — not because of ideological commitment but because their remote, traditional smallholder farming communities have always used low-chemical methods, making formal organic certification a natural next step rather than a radical change in practice.
Over-Extraction
Over-extraction occurs when too much of the coffee’s soluble material is dissolved during brewing. It may result from a grind that is too fine, excessive brewing time, water that is too hot, or excessive agitation during the brewing process.
An over-extracted coffee often tastes bitter, dry, or astringent, with the pleasant sweetness and acidity masked by harsher compounds extracted later in the brewing process. Preventing over-extraction usually involves using a coarser grind, shortening the brew time, reducing agitation, or lowering the brewing temperature to maintain a balanced extraction.
See also: Extraction, Under-Extraction, Agitation, Brew Time.
P
Parainema
Parainema is a modern Arabica coffee variety developed in Honduras for its excellent resistance to coffee leaf rust and its ability to thrive in high-altitude growing conditions. A hybrid derived from the Sarchimor group, it has become increasingly popular among specialty coffee producers due to its resilience, high yields and distinctive cup quality. Well-grown Parainema coffees often display vibrant floral aromas, bright citrus acidity and notes of tropical fruit, stone fruit and sweet caramel, making it one of Central America’s most promising contemporary coffee varieties.
Origin: Honduras
Species: Coffea arabica
Parentage: Sarchimor hybrid
Cup Profile: Floral, citrus, tropical fruit, caramel
Body: Medium
Acidity: Bright and lively
Best Suited For: Filter coffee, pour-over and light to medium roasts
This variety has gained international recognition in recent years, with Honduran Parainema coffees frequently achieving high scores in specialty coffee competitions and showcasing the country’s growing reputation for producing exceptional Arabica beans.
Parchment Plant
The thin, papery protective layer that surrounds the coffee bean inside the cherry, sitting just outside the silver skin. In conventional processing, the parchment is kept intact until the bean has dried to stable moisture levels, then removed by dry-milling. In Indonesia’s Giling Basah process, parchment is removed while the bean is still damp — a key step that gives Sumatran coffee its distinctive character.
Peaberry Plant
A natural mutation in which only one seed develops inside a coffee cherry instead of the usual two. The single seed, with no second bean to share space with, grows small, dense, and rounded — shaped like a pea rather than the flat-sided standard bean. Occurs in roughly 5% of all harvests. Tanzania’s Peaberry (TZPB) is one of the most celebrated grades in specialty coffee. Peaberries roll more freely in the roasting drum, producing more even heat distribution and a consistent roast.
Phin filter Brewing
A small, simple Vietnamese gravity-drip coffee filter that sits directly on top of a glass. Coffee grounds are placed in the chamber, hot water is added, and the brew drips slowly through into the glass below over approximately 5 minutes. No paper, pressure, or electricity required. The traditional method for brewing Vietnamese Robusta, typically served over sweetened condensed milk — cà phê sữa đá when iced.
Pluma Hidalgo Variety
Mexico’s most celebrated coffee variety — a mutation of the Typica variety named after the town of Pluma Hidalgo in Oaxaca where it was first identified. Inherits Typica’s characteristic clarity and clean sweetness, adapted over generations to the specific high-altitude conditions of Oaxaca’s Sierra Madre mountains.
Pour over Brewing
A manual filter brewing method in which hot water is poured slowly and steadily over ground coffee in a filter (paper or metal), allowing it to drip through into a vessel below. Produces a clean, clear cup with full control over extraction variables. The V60 is the most widely used pour-over brewer in specialty coffee. Ideal for delicate, high-acidity origins like Ethiopia, Kenya, and Costa Rica.
Pulped natural Processing
Also called honey process — a processing method in which the coffee cherry’s outer skin is removed but the mucilage is left on the bean during drying. Sits between fully washed (no mucilage) and natural (whole cherry intact). Produces sweetness and body from the retained fruit sugars while maintaining more clarity than a fully natural coffee. Brazil is the world’s largest practitioner of pulped natural processing.
Pu’er coffee Origin
A marketing term used for specialty Arabica coffee from the Pu’er region of Yunnan, China — named after the area’s famous fermented tea. The name evokes the fermentation expertise that defines both the tea and coffee produced in this region, and is increasingly used by specialty buyers and roasters to distinguish premium Yunnan lots from commodity-grade Chinese coffee.
Pulse Pour
A pulse pour is a pour-over brewing technique in which the total brew water is added in a series of small, controlled pours rather than in one continuous stream. After the initial bloom, the brewer pours measured amounts of water, allowing the water level to fall between each addition before beginning the next pour.
Pulse pouring increases agitation and repeatedly introduces fresh water to the coffee bed, helping to promote even extraction and giving the brewer greater control over flow rate, contact time, and flavour development. Depending on the recipe, it can enhance sweetness, clarity, and body, although excessive agitation may lead to over-extraction or increased bitterness. Pulse pouring is commonly used with brewers such as the V60, Kalita Wave, and Origami Dripper.
See also: Bloom, Continuous Pour, Agitation, Extraction, Pour-Over Brewing.
R
Raised bed drying Processing
A drying method in which coffee beans or cherries are spread on elevated mesh or slatted tables rather than on the ground or concrete patios. Allows air to circulate 360° around the bean, producing more even and hygienic drying. Prevents the earthiness and off-flavours associated with ground-level drying in humid conditions. Standard practice in Thailand, Ethiopia, and quality-focused producers across East Africa.
Robusta Species
Coffea canephora — the second most widely grown coffee species, accounting for roughly 40% of global production. Hardier and more disease-resistant than Arabica, thrives at lower altitudes and in hotter, more humid climates. Contains nearly double the caffeine of Arabica. Known for a bold, earthy, bitter profile and exceptional crema production in espresso. Vietnam is the world’s largest Robusta producer; Uganda is one of its original natural homes. When grown at altitude and processed carefully (as in India’s Kaapi Royale), Robusta can produce surprisingly complex and high-quality cups.
Royal Project History
A Thai agricultural development initiative launched in 1969 by King Bhumibol Adulyadej, aimed at replacing opium cultivation in the northern highland communities of the Golden Triangle with sustainable alternative crops, primarily coffee. The Royal Project Foundation continues to operate today, overseeing quality standards across dozens of highland farming communities and producing some of Thailand’s most respected specialty lots.
S
SL28
SL28 is one of the world’s most celebrated Arabica coffee varieties, renowned for producing exceptional cup quality and some of the finest coffees in Kenya. It was developed in the 1930s by Scott Agricultural Laboratories (SAL)—often abbreviated to SL—as part of a breeding programme to identify coffee varieties with high yields, excellent flavour, and adaptability to East African growing conditions.
SL28 thrives at high elevations with well-defined wet and dry seasons. Although it is relatively susceptible to diseases such as Coffee Leaf Rust and Coffee Berry Disease, it remains highly prized because of its outstanding flavour profile. Coffees produced from SL28 are typically characterised by vibrant acidity, a full, juicy body, and complex notes of blackcurrant, citrus, red berries, tropical fruit, and brown sugar, often with a long, wine-like finish.
While closely associated with Kenya, SL28 has also been successfully cultivated in countries including Uganda, Rwanda, Burundi, Malawi, Zambia, Zimbabwe, and parts of Latin America, where it continues to be valued for its exceptional cup quality.
Today, SL28 is regarded as one of the benchmark varieties in specialty coffee and frequently appears in national coffee competitions and international barista championships.
SL34
SL34 is a renowned Arabica coffee variety developed by Scott Agricultural Laboratories (SAL) in Kenya during the 1930s. Like SL28, it was selected as part of a breeding programme to identify coffee trees capable of producing outstanding cup quality while performing well in Kenya’s diverse growing regions.
SL34 was originally selected from French Mission Bourbon stock grown on a single estate in Kenya. It is particularly well adapted to areas with reliable rainfall and fertile soils, where it produces high-quality cherries with exceptional sweetness and complexity. Although susceptible to Coffee Leaf Rust and Coffee Berry Disease, SL34 remains one of the most highly regarded varieties in specialty coffee because of its remarkable flavour potential.
Coffees produced from SL34 are typically known for their rich body, bright yet balanced acidity, and layered notes of blackcurrant, ripe berries, citrus, stone fruit, caramel, and dark chocolate. Compared with SL28, SL34 often delivers a slightly fuller mouthfeel and greater sweetness, while retaining the vibrant fruit character that has made Kenyan coffee famous worldwide.
Today, SL34 is widely cultivated throughout Kenya and is frequently grown alongside SL28. Many of Kenya’s finest coffees contain both varieties, with each contributing to the country’s distinctive flavour profile and international reputation for exceptional quality.
S.795 Variety
A heritage Arabica variety developed specifically for Indian growing conditions, producing a notably smooth, full-bodied cup. One of the two most important Arabica varieties in India’s specialty coffee industry alongside Kent. Widely grown in the shade-grown estates of Coorg and Chikmagalur in Karnataka.
Scott Laboratories (SL) varieties Variety
A family of Kenyan coffee varieties developed in the 1930s by the colonial Scott Laboratories agricultural research station. SL-28 and SL-34 are the two most celebrated, together producing Kenya’s characteristic electric acidity and intense fruit complexity. SL-28 contains unusually high phosphoric acid, responsible for Kenya’s bright, grapefruit and blackcurrant character. Both varieties are demanding to grow but produce cup quality unmatched by almost any other Arabica cultivar.
Shade-grown Production
Coffee cultivated under a forest or tree canopy rather than in direct full sunlight. Shade reduces light intensity, slowing cherry development, concentrating sugars, and producing a denser, more complex bean. Also provides a natural ecosystem that controls pests without synthetic inputs. India is the only major coffee-producing country where all coffee is grown under full shade — a practice born from the dense forest environment where its first trees were planted in the 17th century.
SHB / SHG Grading
Strictly Hard Bean (SHB) and Strictly High Grown (SHG) — altitude-based quality classifications used in Central America, particularly Guatemala, Honduras, and Costa Rica. SHB/SHG denotes coffee grown above approximately 1,350 metres, where cooler temperatures produce denser, harder beans associated with superior cup quality. Always worth looking for on bags from Central American origins.
Single origin Production
Coffee sourced from one specific country, region, farm, or cooperative — as opposed to a blend combining beans from multiple origins. Single-origin coffee allows the drinker to taste the specific character of a particular place, variety, and processing method without the averaging effect of blending. Most of the origins covered in The Coffee Guide are best experienced as single-origin coffees.
Specialty coffee Industry
Coffee that scores 80 points or above on the Specialty Coffee Association’s 100-point quality scale, assessed by trained Q-graders evaluating aroma, flavour, acidity, body, balance, and other attributes. Specialty coffee represents the top tier of the global coffee market — typically traceable to a specific origin, variety, and processing method, and roasted to highlight rather than mask its natural character.
T
Terroir Geography
A French term borrowed from wine, describing the complete natural environment in which a crop is grown — altitude, soil composition, rainfall, temperature, and microclimate — and the way that environment expresses itself in the final flavour. Every coffee origin in this guide has a distinct terroir that shapes its character: volcanic soil in Guatemala and Indonesia, cloud forest mist in Honduras, monsoon winds on India’s Malabar Coast.
Typica Variety
One of the oldest cultivated Arabica varieties and the genetic ancestor of many modern cultivars — including Bourbon, Caturra, Catuai, Maragogype, and Pluma Hidalgo. Typica was the variety carried from Yemen to India by Baba Budan in the 17th century, and subsequently spread by the Dutch and French across the world’s coffee-growing regions. Known for a clean, sweet cup with good complexity but relatively low yield.
TZPB Grading
Tanzanian Peaberry — a legendary specialty grade denoting naturally occurring single-seed (peaberry) beans from Tanzania’s highland Arabica regions, particularly around Mount Kilimanjaro. TZPB is actively sought by specialty buyers and collectors for its sweetness, density, and the focused clarity of its winey, blackberry-toned acidity.
Total Dissolved Solids (TDS)
Total Dissolved Solids (TDS) is a measurement of the concentration of dissolved coffee compounds in a brewed cup. Expressed as a percentage, it indicates the strength of the coffee by measuring how much of the beverage consists of dissolved solids rather than water.
TDS is commonly measured using a digital coffee refractometer, which analyses how light is refracted as it passes through a sample of brewed coffee. A higher TDS indicates a stronger, more concentrated beverage, while a lower TDS indicates a lighter-bodied brew. It is important to note that strength and extraction are not the same: a coffee can have a high TDS but still be under-extracted, or a low TDS and yet be over-extracted, depending on how it was brewed.
When used alongside Extraction Yield, TDS provides brewers with an objective way to evaluate brewing performance and improve consistency. However, numerical measurements should always complement, rather than replace, sensory evaluation, as the ultimate measure of coffee quality is its flavour.
U
Under-Extraction
Under-extraction occurs when too little of the coffee’s soluble material is dissolved during brewing. This usually results from a grind that is too coarse, water that is too cool, insufficient brewing time, an inadequate coffee-to-water ratio, or uneven extraction caused by poor technique.
Coffee that is under-extracted often tastes sour, sharp, thin, or lacking in sweetness and body because many of the desirable sugars and balanced flavour compounds remain in the grounds. Correcting under-extraction typically involves grinding finer, increasing brew time, raising the water temperature, or improving pouring technique to achieve a more even extraction.
See also: Extraction, Over-Extraction, Grind Size, Water Temperature.
V
V60 Brewing
A pour-over coffee dripper designed by Hario (Japan), named for its 60-degree angled cone shape. One of the most widely used specialty brewing tools in the world. Uses a paper filter that removes oils and sediment, producing a clean, clear cup. The spiral ridges inside the cone allow air to escape and coffee to drip freely. Ideal for bright, aromatic origins — Ethiopia, Kenya, Colombia, Costa Rica, Tanzania.
Volcanic soil Geography
Soil formed from volcanic ash and rock, characterised by exceptional mineral richness, good drainage, and natural fertility. Found in the growing regions of Guatemala (Antigua, Atitlán), Indonesia (Java, Sumatra), Tanzania (Kilimanjaro), Honduras, and Costa Rica. Volcanic soil acts as a slow-release natural fertiliser for coffee trees, producing dense, high-quality beans with a characteristic mineral complexity in the cup.
W
Washed processing Processing
Also called wet processing — a method in which the coffee cherry’s outer skin is removed immediately after harvest, and the beans are fermented in water tanks for 24–48 hours to break down the mucilage before being washed clean and dried. Produces the cleanest, most transparent expression of a coffee’s terroir, stripping away processing-derived flavours to leave only what grew in the bean itself. The dominant method in Colombia, Kenya, Ethiopia (Yirgacheffe), and most specialty-focused origins.
Wiener Melange
A Wiener Melange (German for “Viennese Blend”) is a traditional Austrian coffee drink made with espresso (or strong coffee), steamed milk, and a generous layer of milk foam. It is one of the signature beverages of Vienna’s famous coffee house culture and is prized for its smooth, balanced flavour and elegant presentation.
Although recipes vary between cafés, a Wiener Melange is typically prepared by combining a single or double shot of espresso with steamed milk in roughly equal proportions before topping it with velvety milk foam. Some traditional versions are served with whipped cream instead of foam, while others may be lightly dusted with cocoa powder or cinnamon. The result is a rich yet mellow coffee with less intensity than a cappuccino and a creamier texture than a café latte.
The drink has been enjoyed in Austria since the nineteenth century and remains a staple of the historic Viennese coffee houses, where coffee is often accompanied by a glass of water and a selection of cakes or pastries. While it shares similarities with the cappuccino, the Wiener Melange is generally milder in flavour and reflects the distinctive traditions of Viennese coffee culture.
Wet-hulling Processing
See Giling Basah.
Whey
Whey is the second major group of proteins found in milk, making up approximately 20% of its total protein content. Unlike casein, whey proteins remain dissolved in the liquid portion of milk and are highly sensitive to heat.
When milk is steamed for coffee, whey proteins unfold and bond together as the temperature rises, helping to strengthen and stabilise the foam created during steaming. This contributes to the silky texture and glossy appearance of well-prepared microfoam. However, if milk is overheated—typically above 70°C—the whey proteins begin to denature excessively, causing the foam to lose its smooth texture and the milk to develop a cooked or slightly sulphurous flavour.
The interaction between whey proteins, casein, and milk fat is essential for producing the creamy consistency and pouring characteristics required for high-quality espresso-based milk drinks.
WUGAR Processing
Washed Ugandan Arabica — the fully washed grade of Ugandan specialty Arabica, grown primarily on Mount Elgon. Washed processing produces a cleaner, brighter cup than DRUGAR, with the chocolate and dark berry character of Uganda expressed with more clarity and less fruit intensity.
Y
Yirgacheffe Origin
A renowned coffee-growing region in the southern highlands of Ethiopia, widely considered the benchmark for specialty Arabica worldwide. Grown at elevations up to 2,200 metres and typically fully washed, Yirgacheffe coffees are celebrated for exceptional floral clarity — jasmine, bergamot, lemon, and peach — and a tea-like lightness that is unlike any other origin. The definitive choice for pour-over and Chemex brewing.
Yeast processing Processing
An experimental processing technique in which cultured yeast strains are deliberately introduced to the coffee fermentation stage to guide and control the development of specific aromatic compounds. Pioneered in Yunnan, China, drawing on centuries of local expertise in fermenting tea. Produces elevated fruity complexity and a wine-like depth unusual in Asian coffee.