Coffee bean
The coffee bean is the seed of the coffee cherry, a fruit grown on trees or shrubs of the Coffea genus, and serves as the primary ingredient for brewing one of the world's most popular beverages after harvesting, processing, roasting, and grinding.[1] Originating in Ethiopia around the 9th century, coffee cultivation spread from the Arabian Peninsula to global tropical regions, with key milestones including Dutch plantations in Indonesia in the 17th century and the establishment of major production in Brazil by the 18th century, transforming it into a cornerstone of international trade.[2] Today, two dominant varieties—Coffea arabica (Arabica), which accounts for about 60% of global production and offers a milder, sweeter flavor with lower caffeine content, and Coffea canephora (Robusta), known for its higher caffeine levels, bitterness, and resilience to harsher climates—define the industry, grown primarily in the "Bean Belt" between the Tropics of Cancer and Capricorn.[1][3] Coffee production involves several critical steps: after hand- or machine-picking ripe cherries, the beans (seeds) are separated via wet or dry processing methods, dried to a moisture content of about 10-12%, and shipped as green beans before roasting at temperatures of 350-550°F to develop aroma, flavor, and color through chemical reactions like the Maillard process.[1][4] Roasting levels vary from light (preserving acidity and origin notes) to dark (enhancing boldness but reducing nuance), influencing the final brew's profile, while decaffeination processes remove at least 97% of caffeine using water, solvents, or supercritical CO₂ to meet standards.[1] Nutritionally, roasted beans contain over 1,000 bioactive compounds, including antioxidants like chlorogenic acids and about 95 mg of caffeine per 8-ounce cup, linked to potential health benefits such as reduced risk of type 2 diabetes and Parkinson's disease when consumed in moderation (up to 400 mg daily).[1] Economically, coffee is a major traded commodity, with global production about 175 million 60-kg bags annually (as of 2024/25) and Brazil leading as the top producer since the mid-19th century.[5] In the United States alone, as of 2022 the industry generates over $343 billion in economic impact yearly, supporting more than 2.2 million jobs through importing, roasting, retailing, and related sectors like dairy and equipment manufacturing.[6] Recent trends show production rising due to improved yields in Brazil and Vietnam, though climate change poses ongoing threats to Arabica crops. Despite its ubiquity—over 2.25 billion cups consumed daily worldwide—challenges persist, including labor exploitation in supply chains, and sustainability efforts to promote shade-grown farming and fair trade practices.[2][7]History and Etymology
Etymology
The word "coffee" entered the English language around 1600, borrowed from Dutch koffie, which itself derived from Turkish kahveh and ultimately from the Arabic qahwah (قهوة), a term originally denoting wine, a type of beverage, or an appetite suppressant brew.[8][9] This linguistic path reflects the beverage's spread from Sufi mystics in Yemen, where qahwah first described a stimulating drink made from roasted coffee seeds, to Ottoman Turkey and then European trade routes.[9] Yemen's early cultivation and export via ports like Mocha facilitated the term's dissemination across the Arab world and beyond in the 15th and 16th centuries.[9] The precise root of qahwah remains debated, with theories linking it to the Ethiopian Kaffa region—where coffee plants likely originated—or to indigenous terms like the Oromo bun or buna, referring to the raw coffee seed and possibly borrowed into Arabic as bunn.[8][10] In Ethiopian traditions, buna denotes both the plant and the beverage, underscoring the region's cultural ties to coffee's early nomenclature.[10] Although commonly called a "bean," the coffee bean is botanically a seed (endosperm) from the fruit of the coffee plant in the Rubiaceae family, not a true bean from the legume family Fabaceae; this misnomer stems from its visual resemblance to legumes like peas or soybeans, a convention that persisted in trade and everyday language since at least the 1680s.[8][11] In modern terminology across major coffee-producing countries, variations reflect local languages: for instance, Portuguese grão de café in Brazil, the world's largest producer, directly translates to "coffee grain" or "bean."[12]Origins and early history
The legendary origins of the coffee bean trace back to Ethiopia around the 9th century AD, where a goat herder named Kaldi reportedly discovered its stimulating effects after observing his goats become unusually energetic from consuming the red berries of the Coffea arabica shrub.[13] This folklore, first documented in the 17th century but set in the Ethiopian highlands near the Kaffa region, marks the earliest known association of coffee with human use, though archaeological evidence suggests wild Coffea plants grew there for millennia prior. In early Ethiopian societies, coffee cherries were primarily consumed as a food rather than a beverage, with tribes grinding the beans and mixing them with animal fat or ghee to form portable, protein-rich energy balls that provided sustenance during long travels or hunts.[14] This practice, observed among Oromo people as late as the 18th century, represented an initial utilitarian application of the bean's nutritional and energizing properties before its transformation into a drink.[13] By the 15th century, coffee cultivation had spread to Yemen, where Sufi monks in monasteries began experimenting with the beans to stay awake during extended night prayers and religious studies, marking the shift from mastication to infusion.[15] Around the 1450s, these monks formalized the roasting and brewing of coffee into a hot beverage, known as qahwa, which gained popularity in Yemeni society for its role in fostering spiritual focus and communal gatherings.[16] The etymological roots of "coffee" likely derive from the Ethiopian Kaffa region, reflecting this African origin.[14] Coffee's early adoption faced resistance; in 1511, the governor of Mecca, Khair Beg, banned its consumption and closed coffeehouses, deeming the drink an intoxicant that promoted idleness and rebellion, leading to public burnings of beans and floggings of drinkers. This prohibition was short-lived, lifted in 1524 by Ottoman Sultan Suleiman the Magnificent, who overturned the theological rulings after intervention from Sufi scholars.[17]Global spread and modern developments
The dissemination of coffee cultivation beyond its Arabian origins began in the early 17th century, driven by trade routes and colonial ambitions. In 1600, the Sufi saint Baba Budan is credited with introducing coffee to India by smuggling seven seeds from Yemen and planting them in the Baba Budan Giri hills of Karnataka, marking the start of commercial cultivation in the region by the mid-17th century.[18] By 1615, Venetian traders brought coffee to Europe through the port of Venice, where it initially faced religious opposition but soon gained popularity among intellectuals and merchants.[2] The Dutch East India Company further expanded cultivation in 1699 by transplanting coffee plants to Java in present-day Indonesia, establishing large-scale plantations that became a cornerstone of their colonial economy.[19] In the Americas, French naval officer Gabriel de Clieu introduced coffee seedlings to the colony of Martinique around 1715, from which the crop spread rapidly to neighboring islands and mainland regions like Haiti and Brazil by the mid-18th century.[20] Commercialization accelerated in the 17th and 19th centuries with the rise of coffee houses and packaged products. The first coffee house in England opened in London in 1652 by Pasqua Rosée, a Greek servant, fostering social and intellectual discourse that popularized the beverage across Europe and its colonies.[21] In the United States, the retail sale of pre-roasted coffee beans began in New York in 1865, when John Arbuckle pioneered mass-produced, individually packaged coffee, revolutionizing consumer access and distribution.[22] The invention of instant coffee in 1901 by Japanese chemist Satori Kato in Chicago provided a soluble powder form, though it was not widely commercialized until 1938, when Nestlé launched Nescafé, making brewed coffee convenient for households and military use.[23] The 20th and 21st centuries saw transformative developments amid global economic shifts. Following World War II, coffee consumption boomed in the United States and Europe due to increased disposable incomes, marketing by brands like Maxwell House, and the widespread adoption of instant varieties, with U.S. per capita consumption peaking at over 46 gallons annually by the 1940s.[24] Decaffeination processes advanced in the 1970s with the commercialization of supercritical carbon dioxide extraction, offering a safer alternative to earlier chemical methods and expanding market options for health-conscious consumers.[25] Fair trade certifications emerged in the 1980s, starting with the Max Havelaar label in the Netherlands in 1988, aiming to ensure equitable prices for smallholder farmers and promote sustainable practices amid volatile global prices.[26] Post-2010 innovations in supply chain technology, such as blockchain platforms like Bext360, have enabled transparent tracing from farm to consumer, verifying origins, quality, and ethical standards to combat fraud and support sustainability.[27] As of 2023, the global coffee industry was valued at approximately $495.50 billion, reflecting its status as a major commodity trade.[28] Post-2020 trends have highlighted surging demand for specialty coffee, with U.S. consumption of high-quality, ethically sourced varieties reaching 55% of adults weekly—a 6% increase since 2020—driven by preferences for single-origin beans, artisanal roasting, and sustainable certifications amid heightened consumer awareness of environmental and social issues.[29]Botany and Varieties
Coffee plant species
The genus Coffea belongs to the Rubiaceae family and is native to tropical regions of Africa, encompassing over 130 accepted species, with two newly confirmed species added in 2025 previously classified under C. liberica.[30][31] While many species exist, only a few are commercially significant for coffee production, primarily Coffea arabica and C. canephora (commonly known as robusta). C. arabica accounts for approximately 60% of global coffee production and yields beans with a milder flavor profile, whereas C. canephora contributes about 40% and contains roughly twice the caffeine content of arabica, typically 2.2% versus 1.2% by dry weight.[32][33] Coffee plants are evergreen shrubs or small trees that can reach heights of 5 to 10 meters in the wild, featuring opposite pairs of glossy, dark green leaves, fragrant white flowers, and drupaceous fruits resembling cherries that typically contain two seeds (beans) per fruit.[34][35] The growth cycle begins with flowering, which is triggered by rainfall after a dry period, leading to fruit maturation over 6 to 11 months depending on the species and environmental conditions—shorter for arabica (7–9 months) and longer for robusta (9–11 months).[36][37] C. arabica thrives at higher elevations of 600 to 2,000 meters, benefiting from cooler temperatures, while C. canephora prefers lower altitudes from sea level to 800 meters in warmer conditions.[37] Among lesser-known species, Coffea liberica produces larger beans than arabica or robusta and exhibits strong resistance to diseases and pests, making it suitable for cultivation in challenging environments; there is renewed interest in C. liberica and related varieties due to their resilience to climate change.[38][39] Coffea racemosa, native to coastal regions of Mozambique and South Africa, yields small beans but offers high productivity relative to its size and tolerance to drought, though its beverage quality is generally considered lower than that of the primary commercial species.[40]Bean anatomy and varieties
The coffee bean is the seed of the coffee cherry, specifically the endosperm that develops within the fruit of the Coffea plant. The cherry's structure encases this seed through multiple protective layers: an outer skin (exocarp), a fleshy pulp (mesocarp), a pectin layer, a hard parchment (endocarp or hull), and a thin silver skin (testa or epidermis) that directly covers the green bean. The bean itself features a central longitudinal slit, a natural groove formed during development that divides the endosperm into two lobes in typical cherries.[41] Key varieties of coffee beans derive primarily from two species: Coffea arabica (arabica) and Coffea canephora (robusta). Within arabica, Typica represents an ancient cultivar serving as the genetic foundation for many modern varieties, characterized by tall stature and vulnerability to coffee leaf rust, while Bourbon, a natural mutation of Typica, produces beans with excellent cup quality potential at high elevations. Geisha, originating from Ethiopian landraces and popularized in Panama, yields beans noted for distinctive floral attributes. Robusta varieties include Kouillou (also known as Quillou), a traditional type valued for its adaptability in lower-altitude regions. Hybrid varieties like Catimor, a cross between Caturra (an arabica cultivar) and Timor Hybrid (an arabica-robusta introgression), offer disease resistance to coffee leaf rust and berry disease, along with large bean size suitable for high-altitude cultivation.[42][43][44][45][46] Bean size and shape vary by species and type, influencing processing and market grading. Arabica beans are typically oval and larger, measuring 10-15 mm in length with a flat side where paired seeds adjoin in the cherry, whereas robusta beans are smaller (8-10 mm), more rounded, and denser. A peaberry variant occurs when a cherry develops only one seed due to incomplete ovule division, resulting in a rounder, smaller bean that receives undivided nutrients from the fruit, often commanding premium value.[47][48] Genetic diversity among coffee beans stems from heirloom landraces, which preserve varied flavor profiles through natural selection in diverse environments, contrasting with commercial hybrids bred for uniformity, yield, and resistance, potentially narrowing sensory traits but enhancing adaptability. Heirloom varieties, such as Ethiopian arabica landraces, contribute complex, region-specific flavors, while hybrids like Catimor prioritize resilience without fully sacrificing quality potential.[49][50]Cultivation and Harvesting
Growing conditions
Coffee cultivation requires specific environmental conditions within the tropical "Bean Belt," a region between approximately 25°N and 25°S latitude, encompassing parts of Central and South America, Africa, the Middle East, and Asia, where consistent warmth and moisture support optimal growth.[51] Ideal temperatures vary by species: Coffea arabica thrives at 15–24°C, while Coffea canephora (robusta) prefers 24–30°C and tolerates hotter, drier conditions but not below 15°C.[47] Annual rainfall of 1,500–3,000 mm is essential, distributed evenly over 7–9 months to promote flowering and fruit development, with relative humidity levels of 60–80% aiding in moisture retention and reducing stress.[47][52] High altitudes, typically 600–2,000 m for arabica and lower for robusta, provide cooler microclimates that enhance bean quality by slowing maturation.[47] Shade-grown systems, which mimic the plant's natural understory habitat by intercropping with taller trees, maintain soil moisture, moderate temperatures, and support biodiversity, contrasting with sun-grown methods that expose plants to full light for higher yields but increase vulnerability to erosion and pests.[53] Volcanic red earth or deep sandy loam soils are preferred, offering excellent drainage and fertility, with a pH of 5–6 to facilitate nutrient uptake; soils below pH 5 may require liming, while heavy clays or waterlogged areas must be avoided to prevent root rot.[54] Propagation typically begins with seeds sown in nurseries for uniform germination, though cuttings from healthy plants ensure varietal consistency; seedlings are transplanted after 6–8 months when they have multiple leaf pairs.[55] Planting density ranges from 1,000–5,000 plants per hectare, often at 2 m × 1.5 m spacing to achieve around 3,333 plants/ha, depending on terrain and shade availability.[55] Fertilization focuses on balanced NPK applications—such as 120 g per mature tree of 15-15-15 NPK annually in split doses—to replace nutrients removed by yields of 1 tonne of green beans, supplemented by dolomite for calcium and magnesium every two years.[56] Major threats include coffee leaf rust caused by the fungus Hemileia vastatrix, which manifests as yellow-orange spores on leaves leading to defoliation and reduced yields, particularly in susceptible varieties below 1,000 m elevation.[57] The coffee berry borer (Hypothenemus hampei), a beetle that tunnels into developing cherries, causes fruit drop and bean defects, exacerbated by poor sanitation.[57] Integrated pest management (IPM) emphasizes preventive cultural practices like resistant varieties (e.g., Catimor), shade management, and orchard hygiene, combined with biological controls such as Beauveria bassiana fungus or alcohol traps, and targeted fungicides like copper sprays only when thresholds are exceeded.[57]Harvesting techniques
Coffee cherries are harvested when they reach peak ripeness, typically indicated by a bright red to deep purple color, depending on the variety and growing conditions.[58] The primary techniques include selective picking, strip-picking, and mechanical harvesting, each suited to different scales of production and quality goals. Selective picking involves hand-harvesting only ripe cherries, requiring skilled laborers to make 4-6 passes through the plantation over the harvest season to ensure uniformity.[59] This labor-intensive method is predominant for high-quality Arabica coffee, as it minimizes the inclusion of unripe or overripe fruit, thereby preserving bean quality.[58] Strip-picking, in contrast, removes all cherries from branches in a single operation, either manually or with basic tools, capturing a mix of ripeness stages. This approach is more common for Robusta varieties or large-scale Arabica plantations where cherries mature more uniformly, such as in Brazil when about 75% of the crop is ripe.[58][59] Mechanical harvesting employs specialized equipment like vibratory or trunk-shaking machines to dislodge cherries onto collection nets, enabling efficient single-pass collection on flat terrains with widely spaced trees. It is increasingly adopted in regions facing labor shortages, with post-2020 advancements in automation, including handheld vibrating devices that significantly increase harvesting efficiency in suitable conditions.[60] Typical yields for mature Arabica plants range from 0.5 to 1 kg of green beans per plant annually under optimal management, while Robusta can achieve higher outputs of 1-2 kg per plant due to its robustness.[61] These figures vary by variety, soil, and climate but highlight the efficiency gains from mechanical methods in high-density fields. Following harvest, initial sorting is crucial to maintain quality; cherries are often floated in water tanks where unripe, damaged, or lightweight fruit rise to the surface and are discarded, ensuring only sound cherries proceed to processing.[62] This density-based separation prevents defects from affecting the final bean grade and supports consistent flavor profiles.[63]Processing
Wet processing
Wet processing, also known as the washed method, involves using water to remove the outer fruit layers from coffee cherries, resulting in green beans with a clean profile suitable for high-quality Arabica coffees.[64] This method begins shortly after harvest, typically within 6-8 hours, to prevent spoilage and initiate controlled biochemical changes.[62] The process starts with depulping, where mechanical equipment such as disc, drum, or screen pulpers removes the outer skin and pulp from the cherries, separating the parchment-covered beans.[62][65] Next, fermentation occurs in tanks, lasting 12-48 hours at 20-25°C, where enzymes and microbes break down the sticky mucilage layer surrounding the parchment; monitoring via pH drop (to 4.0-5.0), texture, or smell ensures optimal duration to avoid over-fermentation.[62][66] Washing follows in channels or tanks with clean water and agitation using squeegees, grading beans by density to remove remaining mucilage and floaters.[62][65] Finally, drying reduces moisture to 10-12% on raised beds or mechanical dryers over 5-14 days, with frequent turning to maintain temperatures below 40°C and prevent defects.[62][66] This method offers advantages including brighter acidity, cleaner flavors, shorter drying times, fewer defects, and improved overall quality, making it ideal for premium Arabica production.[65][66][67] Equipment like pulpers (capacity up to 1,000 kg/hour), fermentation tanks (e.g., 3m x 2.5m x 1m), washing channels, and raised drying tables (holding 10-12 kg/m²) are essential, often set up in wet mills.[62][65] Water consumption can reach up to 40 liters per kg of beans, primarily for pulping, fermentation, and washing, generating wastewater that requires management through settling ponds, vetiver wetlands, or composting of pulp to mitigate environmental impact.[62][67] Regional variations include the fully washed process, dominant in East Africa for its clarity, and the honey process, where partial mucilage is retained during drying for added sweetness while reducing water use.[62]Dry processing
Dry processing, also known as natural processing, involves drying whole coffee cherries without depulping or washing, allowing the fruit's sugars to ferment naturally within the skin during the drying phase.[68] This method is particularly suited to regions with limited water access and is the predominant technique for processing Robusta coffee and a significant portion of Arabica in dry climates.[69] In Brazil, approximately 90% of Arabica production uses dry processing, while in Ethiopia, it accounts for about 65% of output.[70][71] The process begins with harvesting ripe cherries, which are then spread out in a single layer on patios, raised beds, or African-style drying tables to maximize airflow and sun exposure.[72] The cherries must be turned frequently—often several times a day—to ensure even drying and prevent overheating or mold formation, a labor-intensive step that typically takes 2 to 4 weeks depending on weather conditions.[73] Once the cherries reach 10-12% moisture content, they undergo hulling to mechanically remove the dried exocarp, mesocarp, and endocarp, revealing the green coffee beans enclosed in parchment.[68][62] This method offers advantages such as lower operational costs due to minimal equipment and water requirements, making it accessible for smallholder farmers in resource-scarce areas.[74] It also imparts distinctive fruity and complex flavors to the beans, as the prolonged contact with the fruit pulp infuses sweetness and berry-like notes.[75] However, challenges include the risk of over-fermentation or mold growth in high-humidity environments, which can lead to defects if drying is uneven or prolonged.[76] Achieving the critical 10-12% moisture level is essential to avoid quality degradation from fungal contamination.[77] Recent innovations since 2020 have introduced mechanical dryers to enhance efficiency in dry processing, such as static bed dryers that optimize airflow and temperature for faster, more uniform results while reducing labor demands.[78] Technologies like the roto-aerated dryer and CoffeeDryer® systems allow for controlled drying in as little as days rather than weeks, minimizing weather-related risks and improving consistency in humid regions.[79][80]Chemical Composition
Macronutrients
Green coffee beans primarily consist of macronutrients that form the bulk of their dry matter, providing structural integrity and energy potential. These include carbohydrates, proteins, and lipids, which together account for over 80% of the dry weight, with water comprising the remainder in unroasted beans. The composition varies slightly between Coffea arabica and Coffea canephora (robusta) varieties, influenced by genetics and growing conditions.[81] Carbohydrates make up 50-60% of the dry weight in green coffee beans, predominantly in the form of polysaccharides such as cellulose, hemicelluloses, and mannans, which contribute to the bean's structural framework and rigidity. These insoluble carbohydrates, including arabinogalactans and galactomannans, form the cell walls and endosperm matrix, while soluble forms like sucrose and oligosaccharides represent a smaller fraction (around 6-9% in arabica). Their role is primarily structural, supporting the bean's integrity during growth and processing, rather than serving as immediate energy sources.[82][81] Proteins and amino acids constitute 10-13% of the dry weight, existing as storage proteins in the endosperm and free amino acids that influence bean quality. Key free amino acids include glutamic acid, aspartic acid, alanine, and lysine, with glutamic acid often predominant at levels up to 20-30% of total free amino acids. These proteins, mostly albumins and globulins, provide nitrogenous reserves for the developing plant and contribute to enzymatic processes, though they are largely indigestible in their native form.[83][84] Lipids account for 11-17% of the dry weight, primarily as triglycerides (over 75% of total lipids), sterols, and diterpenes such as cafestol and kahweol, which are embedded in the inner layers of the bean. Arabica varieties typically exhibit higher lipid content (15-17%) compared to robusta (7-12%), affecting oil extraction and flavor development during roasting. These non-polar compounds serve as energy reserves and protect against oxidative stress in the seed.[85][86] Green coffee beans contain 10-13% water by weight, which must be maintained within this range to prevent microbial growth and ensure stability during storage. A basic nutritional breakdown per 100 g of green beans (on a wet basis, assuming ~12% moisture) approximates 350-400 kcal, with ~45-55 g carbohydrates, 9-12 g proteins, and 10-15 g lipids, though exact values vary by variety and origin. During roasting, these macronutrients undergo degradation, with carbohydrates and proteins breaking down to form melanoidins and aromas, while lipids partially volatilize.[87][88]| Macronutrient | Approximate % Dry Weight (Arabica) | Key Components | Primary Role |
|---|---|---|---|
| Carbohydrates | 50-60% | Polysaccharides (cellulose, mannans) | Structural support |
| Proteins | 10-13% | Free amino acids (e.g., glutamic acid) | Nitrogen storage |
| Lipids | 15-17% | Triglycerides, diterpenes (cafestol) | Energy reserve |
| Water | 10-13% (wet basis) | N/A | Hydration stability |