Facts About Coffee
Botany & Species
Coffee is the seed of fruits from the genus Coffea, most notably the species C. arabica and C. canephora (“robusta”).
Wild coffee plants are native to the Ethiopian highlands (Kefa/Kaffa), though domestication history is uncertain.
Arabica accounts for the majority of specialty coffee and is generally grown at higher elevations than robusta.
Robusta (canephora) typically contains more caffeine than arabica, contributing to a more bitter, earthy cup.
Coffee seeds are botanically “beans” but are the endosperm of the fruit; each cherry usually contains two.
A single seed (peaberry) forms when only one ovule develops, often producing rounder beans.
Coffee plants are evergreen shrubs or small trees; cultivars vary widely in size and yield.
Arabica is more susceptible to diseases like coffee leaf rust than robusta.
Flavor precursors (acids, sugars, amino acids) formed during growth and processing set the stage for roast chemistry.
Global production is dominated by Brazil, Vietnam, and Colombia, led by Brazil.
Origins & History
Ethiopia is widely regarded as coffee’s birthplace; Yemen was an early hub for cultivation and trade.
The Kaldi goat-herder tale is a legend, not a verified origin story.
By the 15th–16th centuries, coffeehouses spread across the Islamic world and into Europe.
The port of Mocha (Yemen) gave “mocha” its historic association with coffee trade.
Coffee cultivation expanded to the Americas via colonial botanic exchanges in the 18th century.
Espresso culture took root in Italy with the rise of pressure-driven machines in the 20th century.
Coffeehouses historically served as centers for social and intellectual exchange.
Many origin myths persist, but scholarship emphasizes Ethiopian wild progenitors and later dispersal.
“Arabica” reflects early cultivation and transport through the Arabian Peninsula.
Coffee’s global spread intertwined with colonial trade networks and plant expeditions.
Farming & Processing
Processing removes fruit layers and dries seeds from roughly 65–70% moisture to about 12–13% before storage.
Three main processing families: dry/natural, wet/washed, and pulped natural (semi-washed or honey).
Dry (natural): cherries dry whole before hulling, often yielding fruit-forward flavors.
Washed: pulp removed, mucilage fermented/washed off, associated with “cleaner”, more delicate cups.
Pulped natural: skin removed, mucilage dries on the seed; a hybrid of washed and natural.
Controlled “experimental” fermentations (yeasts, temperature) are an emerging avenue to shape cup profile.
Proper sorting (ripe vs. unripe) is critical to uniform processing and flavor. Most specialty coffees are still picked and sorted by hand.
Drying method (patios, raised beds, mechanical) affects moisture uniformity and shelf stability.
Defects (e.g., quakers, insect damage) can result from agronomy or processing errors.
Elevation impacts bean density and acid development, influencing roast approach.
Traceability is harder in large commodity chains than in smallholder microlots.
Moisture and water activity targets are used to reduce mold risk and staling during storage.
Washing steps include fermentation, washing, and often soaking to remove mucilage.
Pulped natural is also called “semi-washed” or “honey” in some producing regions.
Processing choices shape acidity, body, and overall flavor profile in the final brew.
Roasting Science
Roasting transforms green beans via drying, Maillard reactions, caramelization, and pyrolysis.
The Maillard phase (browning) links amino acids and sugars, creating aroma/color compounds (melanoidins).
First crack signals internal pressure fracturing the bean as water vapor and gases expand.
Roast development time after first crack strongly influences sweetness and roast character.
Darker roasts reduce perceived acidity and can mute origin nuances while increasing roast flavors.
CO₂ is produced during roasting and degasses for days to weeks afterward.
Degassing rate depends on roast level and grind size; finer grinds release CO₂ faster.
One-way valves on bags release CO₂ while limiting oxygen ingress to slow staling.
Roast color correlates with soluble yield potential but doesn’t alone predict flavor quality.
Careful roast profiling aims to balance development (sweetness) with retention of volatiles and acids.
Grinding & Extraction Chemistry
Finer grind increases surface area, generally raising extraction (and risk of over-extraction).
The SCA “Golden Cup” target: about 1.15–1.35% TDS at roughly 18–22% extraction yield for brewed coffee.
Water temperature around 92–96 °C (195–205 °F) is widely recommended for filter brewing.
Under-extracted coffee tastes sour/thin; over-extracted tastes bitter/astringent, per brew-control guidance.
Agitation and contact time affect mass transfer and extraction uniformity.
Espresso is a pressure-brewed method; 8–10 bars is a common operating range.
A typical modern espresso starting point is a 1:2 brew ratio (e.g., 18 g in → 36 g out).
Channeling (non-uniform flow through the puck) causes uneven extraction and off-flavors.
Blooming pre-wetting helps release trapped CO₂ in fresh coffee, stabilizing flow.
Refractometers allow objective TDS measurements to guide recipe dialing.
Brewing Methods & Recipes
Pour-over (percolation) extracts as water passes through a bed; grind and pour control are key.
Immersion (e.g., French press) steeps grounds before filtration, often yielding more body.
Cold brew uses room-temp/cold water for long contact times, typically producing lower titratable acidity than hot brews.
Cold brew’s perceived acidity is usually lower, giving a smoother profile for many drinkers.
Espresso shots are small, concentrated extractions under pressure; ratios and time tune taste.
Metal filters (French press) pass more oils/fines; paper filters yield cleaner cups.
Grind size progression (coarse→fine) typically: cold brew/french press → pourover/drip → espresso.
Agitation (stir/swirls) can increase extraction but may raise fines migration in percolation brews.
Dose-to-water ratios near 1:15–1:17 are common starting points for filter brews.
Bypass (adding water post-brew) adjusts strength without changing extraction yield.
Drip machines designed to SCA standards aim to hit target temperature and contact times.
Even bed preparation (flat, level) supports uniform percolation in pour-over.
Espresso water debit/flow controls (and pre-infusion) help reduce channeling.
Coarser grinds and longer steeps in cold brew drive high strength concentrates, later diluted to serve.
Brewer geometry (e.g., flat-bottom vs. cone) influences flow resistance and extraction patterns.
Water, Standards & Equipment
Water chemistry strongly affects flavor; the SCA publishes water standards for brewing.
Classic SCA targets include total hardness and alkalinity in ranges that balance extraction and scale/corrosion risk.
Too-high alkalinity can mute acidity and flavor clarity; too-low can taste sharp and risk corrosion.
Tools exist to evaluate bottled water composition against SCA targets.
Temperature stability in brewers is critical for repeatability and cup consistency.
The SCA Golden Cup standard connects sensory preference to measured strength and extraction.
Espresso “9-bar” tradition is widespread, though some workflows use different pressures.
Paper filters remove more diterpenes (like cafestol) than metal, which can affect mouthfeel and health markers.
Poor water quality (excess minerals or chlorine) can impair extraction and taste.
Scale in equipment reduces heat transfer and flow; water treatment helps prevent it.
Caffeine & Health
For most healthy adults, up to about 400 mg caffeine/day is considered an upper bound not generally associated with negative effects by U.S. regulators.
A 12‑oz brewed coffee can range roughly 113–247 mg caffeine; variability depends on brew method and coffee.
During pregnancy, major U.S. medical guidance recommends limiting caffeine to under 200 mg/day.
Reviews associate moderate coffee consumption with reduced risk of several chronic diseases, though context matters.
Exceeding roughly 400 mg/day may increase risks for some people (e.g., palpitations, blood pressure).
Cold brew is often perceived as gentler due to lower acidity, though antioxidant content can be higher in hot brews.
Caffeine sensitivity varies; body mass, medications, and genetics influence effects.
Caffeine passes through the placenta and into breast milk; individualized medical guidance is advised.
Energy drinks can contain additional stimulants; “mg caffeine” isn’t the whole risk picture.
Brewed coffee’s health impact depends on both dose and preparation (e.g., paper vs. unfiltered).
Storage & Freshness
Freshly roasted beans release CO₂ for days to weeks; packaging valves let gas out and limit oxygen in.
Grind just before brewing to reduce oxidation and volatile loss.
Cool, dark, airtight storage slows staling; avoid humidity and heat.
Freezing in well-sealed, portioned bags can preserve freshness longer by slowing reactions.
Canned vacuum-packed coffee is degassed before sealing, trading some “freshly roasted” aromatics for shelf life.
Trade, Sustainability & Market Context
The International Coffee Organization (ICO) maintains a large public database covering trade, prices, production, and consumption.
ICO outlooks track supply/demand balances by crop year (October–September).
Labor practices in coffee supply chains are under scrutiny; NGOs and regulators investigate abuses in some regions.
Colombia has reported strong harvests in recent years, with cautions about variability in future cycles.
Country, variety, process, and market channel (commodity vs. specialty) all influence the price producers receive.
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