Know your coffee

Coffee is the seed of a fruit. The plant is a tropical evergreen shrub in the Coffea genus. It flowers white and jasmine-scented, then sets small green fruits called cherries. Each cherry usually contains two seeds pressed flat against each other — the "beans". When only one seed forms and it grows round, it is called a peaberry.

From flower to ripe cherry takes roughly 7–9 months for Arabica. The plant takes three to four years to start producing and is commercially productive for 20–30 years. It prefers stable warm temperatures, a defined wet/dry cycle, and — for the best cups — altitude.

Of around 130 known Coffea species, three matter commercially:

Arabica (Coffea arabica)

About 60–70% of world production. Grown at altitude (typically 1,000–2,200m), more delicate, more disease-prone, lower in caffeine (~1.2%). Sweeter, more aromatic, more acidic. Practically all specialty coffee is Arabica.

Robusta (Coffea canephora)

Grown at lower altitudes, hardier, higher yielding, roughly twice the caffeine (~2.2%). More bitter, more rubbery, heavier in body, with more crema in espresso. The backbone of cheap blends, traditional Italian espresso, and most instant coffee. A small specialty Robusta scene exists and can be genuinely good.

Liberica (Coffea liberica, incl. Excelsa)

A tiny share of global supply. Larger, irregularly shaped beans, polarising flavour — smoky, woody, sometimes jackfruit-like. Common in the Philippines and parts of Malaysia and West Africa.

Within Arabica there are dozens of cultivated varieties, each with its own flavour ceiling, yield, disease resistance and altitude preference. A few worth knowing:

• Typica & Bourbon — the two ancestral lines most others descend from. Classic, balanced, sweet.
• SL28 & SL34 — selections developed in Kenya. Famous for blackcurrant-like acidity.
• Gesha / Geisha — Ethiopian-origin, made famous in Panama. Floral, jasmine, bergamot. Auction prices are eye-watering.
• Catuai, Caturra, Mundo Novo — workhorse Latin American cultivars.
• Pacamara, Maragogipe — large-beaned, often complex and unusual.
• Heirloom — a catch-all for the wild and semi-wild Ethiopian varieties; genetically the most diverse coffee on Earth.
• Castillo, Marsellesa, Centroamericano — modern hybrids bred for leaf rust resistance.

"Terroir" is the sum of the place: altitude, soil, rainfall, temperature, sunlight, shade, and surrounding ecosystem. A few rules of thumb:

• Altitude — higher and cooler slows cherry maturation. Beans become denser and develop more acidity, sweetness and complexity.
• Soil — volcanic soils (Ethiopia, Central America, Indonesia) are famous for the cup quality they produce.
• Shade — slows ripening, supports biodiversity, often improves flavour and bird habitat.
• Microclimate — fog, cloud cover and a strong day–night temperature swing tend to produce more interesting coffees.

How cherries are picked is one of the most underrated quality factors.

• Selective hand-picking — pickers come back to the same tree multiple times and only pick perfectly ripe red cherries. Labour-intensive, expensive, and the standard for specialty.
• Strip picking — pickers strip everything from the branch in one pass: ripe, unripe, overripe. Cheap, fast, lower quality.
• Mechanical harvesting — common in Brazil's flat farms. Modern machines can be selective by vibration frequency, but it still mixes maturity stages.

Processing is how the seed is removed from the cherry and dried down to a stable moisture content. It has a huge impact on flavour.

Washed (wet)

Skin and pulp are removed mechanically; the sticky mucilage is fermented off in water tanks; the seed is washed and dried. Result: clean, transparent, often more acidic. The terroir and variety speak loudest.

Natural (dry)

Whole cherries are dried in the sun on patios or raised beds for weeks, then hulled. Result: heavier body, fruit-forward, often berry, wine, or tropical fruit notes. Riskier — easy to over-ferment.

Honey / pulped natural

Skin removed, mucilage left on, dried with the sticky layer intact. White, yellow, red and black honey describe how much mucilage and how slow the dry. Sits between washed and natural — sweet, syrupy, balanced.

Anaerobic & carbonic maceration

Cherries are sealed in tanks (sometimes flushed with CO₂) and fermented under controlled, oxygen-free conditions. Can produce wild, intense and divisive cups — cinnamon, strawberry candy, fermented funk.

Wet-hulled (Giling Basah)

An Indonesian specialty. Beans are hulled while still wet, leading to the characteristic deep, earthy, herbal Sumatran profile.

Green coffee is graded by bean size, density, defect count and (for specialty) by cup score. The Specialty Coffee Association (SCA) calls anything 80+ on a 100-point cupping scale "specialty". Most commodity coffee never gets cupped at all.

Common defect names: quakers (under-ripe beans that won't roast), blacks(over-fermented), sours, broken, insect-damaged. A clean cup starts with hand-sorting them out.

"Single origin" just means the coffee in the bag comes from one place. How strict that "one place" is can vary widely:

• Single country — the loosest version. "Ethiopia" or "Colombia" with no further detail.
• Single region — Yirgacheffe, Huila, Nyeri.
• Single cooperative or washing station — coffee from many small farmers, processed together.
• Single farm (estate) — one producer, often one elevation band.
• Single lot / micro-lot — one variety, one processing, one harvest day or tank. The most traceable.

The point of single origin is that it should taste of somewhere. An Ethiopian Yirgacheffe should taste different from a Kenyan Nyeri. A washed lot from a farm should taste different from a natural lot from the same farm.

• Smaller volumes. A single farm or lot produces a fraction of what a big blend uses, so the per-kilo cost is higher.
• Higher quality bar. Selective picking, careful sorting, and only the top of the harvest making it in.
• Direct, fairer pricing. Specialty buyers often pay multiples of the C-market price directly to producers.
• Careful processing & storage. Raised beds, controlled fermentation, GrainPro bags, refrigerated containers.
• Lighter roasting. Less weight loss in the roaster, but the green coffee itself costs more to begin with.
• Slower logistics. Smaller shipments, more handling, more inspection.

A blend mixes coffees from two or more origins to hit a target flavour and to keep that flavour stable across the year. A roaster might combine a sweet Brazilian for body, a washed Central American for clarity, and an Ethiopian for aromatics.

Blends are not a lower tier — they are a different goal. A house espresso blend is designed to be consistent week after week and to play well with milk. Commodity blends, on the other hand, are usually built around price and roasted dark to hide variability.

Roasting transforms a hard, grassy green seed into something soluble and aromatic. Inside the roaster the bean dries, then browns (Maillard reactions), then audibly cracks twice as gases expand.

• Light roast — stopped just after first crack. Highest acidity, most origin character. Common for filter-focused specialty.
• Medium roast — between first and second crack. Balanced, sweeter, less acidic. The default for most coffees.
• Dark roast — into or past second crack. Roast flavours dominate (smoky, bittersweet, chocolatey). Origin character mostly burned off.

Lighter roasts retain more of the bean's original mass and caffeine; dark roasts lose more weight but their oils migrate to the surface (the shine you see on traditional espresso beans).

Roasted coffee needs ~5–10 days to "rest" (degas CO₂) before it brews well, then is usually at its best for 3–6 weeks. Whole beans last meaningfully longer than ground.

Store in an opaque, airtight container at room temperature. Coffee's enemies are oxygen, heat, light, and moisture — in that order. The fridge is moist and full of food smells; the freezer is fine for long-term storage of unopened bags.

Grinding releases aromatics and exposes the surface area that water can extract. Once ground, coffee stales within minutes, not weeks. A decent grinder is the single biggest upgrade most home brewers can make.

• Burr grinders (conical or flat) produce uniform particle sizes. Recommended for any brew method.
• Blade grinders chop unevenly. Avoid for anything beyond emergency use.
• Grind size matters more than ratio. Espresso is fine like powdered sugar; pour-over is medium like table salt; French press is coarse like breadcrumbs.

A brewed coffee is over 98% water. Water hardness, mineral content and pH all affect extraction and taste. The SCA target is roughly 150 mg/L total dissolved solids, with a balance of calcium, magnesium and bicarbonate.

Practical version: filtered water tastes better than chlorinated tap water. Bottled "low mineral" spring water (e.g. Volvic) is a safe default. Distilled or RO water on its own tastes flat — it needs minerals added back.

Pour-over (V60, Kalita, Chemex)

Hot water is poured slowly through ground coffee in a paper filter. Highlights clarity, acidity and aromatics. Best for lighter roasts and single origins.

French press (immersion)

Coffee steeps in hot water for ~4 minutes, then a metal mesh plunges down. Heavier body, more sediment, more oils. Forgiving to grind size.

AeroPress

Hybrid immersion + pressure brewer. Versatile, fast, very travel-friendly. Capable of espresso-ish concentrates or filter-style cups depending on recipe.

Moka pot

Stovetop, low-pressure brewer. Strong, syrupy coffee — not technically espresso, but a great affordable approximation.

Cold brew & iced

Cold brew steeps coarse coffee in cold water for 12–24 hours, producing a sweet, low-acid concentrate. Iced (Japanese) brews hot directly onto ice — keeps acidity and aromatics, ready in minutes.

Espresso pushes hot water (~93°C) through finely-ground, tamped coffee at ~9 bars of pressure, in 25–35 seconds. The result is concentrated, with crema (a foam of CO₂ and emulsified oils) on top.

Milk drinks (cappuccino, flat white, latte) work because steamed milk's lactose, proteins and fats coat the bitter compounds and amplify chocolatey, nutty, caramel notes. This is why espresso blends are often built with milk in mind.

All decaf starts with green coffee soaked in water or steam, then caffeine is removed by one of:

• Swiss Water Process — uses water and a charcoal filter. Chemical-free, gentle on flavour.
• CO₂ process — supercritical CO₂ selectively pulls caffeine. Excellent flavour retention, used for higher-end decafs.
• Sugarcane / EA (Ethyl Acetate) — solvent naturally derived from fermented sugarcane. Common in Colombia, often quite sweet.
• MC (Methylene Chloride) — direct solvent process. Cheaper, residues are negligible but the method has poor PR.

Modern decaf can be very good. It will rarely match the same coffee with caffeine, but it is a long way from the dusty supermarket decaf of 20 years ago.

Instant coffee is brewed coffee that has been dried back into soluble crystals or powder. Two methods dominate:

• Spray-dried — hot brewed coffee is sprayed into a tower of hot air. Cheap and fast, but high heat strips delicate aromatics.
• Freeze-dried — coffee is frozen, then water is removed under vacuum. More expensive, but it keeps far more flavour.

Most mass-market instant uses cheaper Robusta for caffeine and crema, often from blended commodity-grade lots. A small but growing category of specialty instant uses freeze-dried single-origin Arabica and tastes much closer to fresh brew — at a price closer to fresh beans.

Most of the world's coffee is still traded as a commodity on the New York "C market", whose price often sits below the cost of production for many farmers. The ripple effects are real: rural poverty, generational flight from farming, and shrinking land under coffee.

Certifications you'll see on bags:

• Fair Trade — guaranteed minimum price + a community premium.
• Rainforest Alliance / UTZ — environmental and social standards.
• Organic — no synthetic pesticides or fertilisers.
• Direct Trade — not a certification, a relationship: roaster buys directly from producer, usually well above C-market.

Climate change is shrinking the suitable coffee-growing band by the decade. Expect more shade-grown coffee, more rust-resistant hybrids, and a slow migration to higher altitudes.

A single shot of espresso has roughly 60–80mg of caffeine. A typical filter mug (250ml) has 100–180mg. Robusta has about double the caffeine of Arabica. Lighter roasts have marginally more caffeine by weight, but the difference is small.

Caffeine has a half-life of 5–6 hours in most adults. A 3pm coffee is still half "active" at 9pm. For sleep quality, many people find a cut-off of early afternoon helpful.

• Cherry — the fruit of the coffee tree.
• Parchment — papery layer around the green seed.
• Mucilage — sticky sugar layer between skin and parchment.
• Cupping — standardised tasting protocol used to score coffees.
• Crema — the foam on top of an espresso shot.
• TDS — total dissolved solids; how strong a brew is.
• Extraction — what % of the ground coffee's mass dissolved into the cup. Specialty target is roughly 18–22%.
• C-market — the global commodity price for Arabica.
• Lot — a discrete batch of coffee, usually one variety / process / day.