☕ Coffee: From Bean to Cup

What you’ll learn

1. Coffee Is a FruitUnderstand that coffee is the seed of a fruit and that two species — arabica and robusta — define most of its character.What we call a coffee bean is the seed of a small stone fruit, the coffee cherry. Two species dominate: arabica (majority of production, ~1.2% caffeine, aromatic and acidic, high-altitude) and robusta (~2.2% caffeine, harsher and cheaper, hardy and low-altitude). Caffeine is the plant's natural insecticide, so the harsher species is also the more caffeinated.
2. Why Altitude MattersExplain how altitude and terroir shape arabica flavor before any processing or roasting.Air cools ~6°C per 1,000 m of elevation, so high-grown arabica ripens slowly, developing more sugars, acids and aromatic compounds and a denser seed — the basis for 'strictly hard bean' grading. Beyond altitude, the full terroir (soil, rainfall, shade, latitude) gives origins like Yirgacheffe, Sumatra and Kenya their signatures.
3. Processing: The Biggest LeverDistinguish washed, honey and natural processing and predict their flavor effects.After picking, the seed must be freed from the fruit and dried, and how that's done is often the biggest single flavor decision. Washed processing removes fruit early for clean, bright, acidic cups; natural dries the whole cherry for fruitier, heavier, lower-acid cups; honey leaves some mucilage on for a sweeter middle ground.
4. The RoastDescribe the roasting chemistry and how roast level trades origin flavor for roast flavor.Roasting cooks flavorless green coffee via the Maillard reaction (~150°C) and caramelization, with first crack near 196°C. Light roasts preserve origin acids and aromatics; dark roasts replace them with roasty, bittersweet pyrolysis flavors. Caffeine is heat-stable, so dark roast does not meaningfully contain more caffeine.
5. Grind and ExtractionUse extraction theory and the two knobs — grind size and time — to control a cup.Brewing is hot water dissolving flavor from grounds in order (acids first, sweetness next, bitterness last). Under-extraction tastes sour/thin; over-extraction tastes bitter/harsh. Grind size and contact time are the two main controls. The SCA Golden Cup targets ~18–22% extraction and 1.15–1.35% strength, near a 55 g/L (1:18) ratio.
6. The Brewing MethodsSort brewing methods into immersion, pour-over and pressure and see the shared physics.Immersion (French press) steeps grounds for full body; pour-over (V60, Chemex, drip) percolates water through a bed for a cleaner, brighter cup; pressure (espresso) forces water through fine grounds in seconds. All manipulate the same two variables — surface area and time — and espresso's speed makes it especially sensitive to grind.
7. The Honest EconomicsExplain how commodity pricing and the value chain leave growers a small share.Most arabica is sold as a commodity priced by the global 'C' futures benchmark (37,500 lb contracts, cents per pound), which swung above $4/lb in early 2025 on supply scares. A long chain of intermediaries and weak grower bargaining power mean farmers often capture only a small fraction of the retail price; specialty and direct trade attempt to pay more for quality.
8. Fixing a Bad CupDiagnose a flawed cup by walking back up the bean-to-cup chain.Sour and thin means under-extraction (grind finer/brew longer); bitter and harsh means over-extraction (grind coarser/brew shorter); weak but not sour means too little coffee for the water; balanced but boring means the beans themselves are the limit. Four complaints map to four links in the chain.

Questions this course answers

Grounded in trusted sources

• International Coffee Organization — Coffee Report & Outlook, Dec 2023
• Specialty Coffee Association — Golden Cup brewing standard & Brewing Control Chart
• ICE — Coffee C Futures product specifications; Daily Coffee News (May 2025)
• World Coffee Research — variety and processing references
• HPLC caffeine analyses of arabica vs robusta green coffee

Every Wunder lesson is built from real, reputable sources — never invented.

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