Green Coffee

A green coffee lot is dried, hulled beans identified by origin, species, processing method, crop year, and grade. Two species carry the commercial trade. Arabica is the higher-priced, more aromatic, more demanding species, grown at altitude; robusta is hardier, higher in caffeine, harsher in the cup, and cheaper, and dominates instant coffee and blends. They trade on separate markets at separate prices and are never treated as interchangeable.

Processing method travels with the lot as part of its identity, because a washed and a natural coffee from the same farm are recognisably different products. So does crop year: coffee ages, and a fresh crop and a past crop are distinguished commercially even where the older lot is perfectly sound.

Coffee grading is unusual in combining physical measurement with sensory assessment. The physical side counts and classifies defects in a sample — black beans, sour beans, insect-damaged beans, broken beans, and foreign matter — and screens the beans by size, since a lot of uniform size roasts evenly and a mixed one does not. Density, colour, and moisture are assessed alongside.

The sensory side is cupping: the coffee is roasted, brewed, and tasted under a standardised procedure, and scored. For the specialty trade the cup score is the grade that matters most, and a lot with a perfect defect count and a dull cup will not command a specialty price. Grading systems are national and vary widely — origins classify by altitude, by screen, by defect count, or by combinations of these — so a grade name means something only in the context of its origin's system.

• Black and sour beans — the classic primary defects, from overripe or damaged cherries
• Insect-damaged beans, notably from the coffee berry borer
• Broken, chipped, and cut beans from hulling and handling
• Foreign matter — stones, sticks, and husk fragments
• Faded, bleached, and mouldy beans from drying or storage problems
• Uneven screen size within a lot, causing uneven roasting

Green coffee behaves like other dried seed commodities: it is hygroscopic, and its moisture governs whether it stores safely. Dried insufficiently, it moulds and carries an ochratoxin risk that importing jurisdictions regulate; dried too far or too fast, the bean is damaged and the cup suffers. The moisture band that satisfies both constraints is narrow, and it is set by contract and by origin standard rather than by any universal figure.

Even correctly dried and stored, green coffee ages. It fades in colour, loses aroma and acidity, and develops the flat, woody character the trade calls past crop — not spoilage, just decline, and it is why crop year is part of a lot's identity. Storage in warehouses at origin and destination is managed against humidity, temperature, and taint, coffee being notably good at absorbing odours from whatever it is stored beside. Hermetic and vacuum packaging is used to slow the decline for high-value lots.

Green coffee moves from producing countries to roasters, mostly in bags in containers, increasingly in bulk liners, and — for the highest-value lots — in vacuum or barrier packaging. Its price is discovered on futures markets for the two species, with physical lots trading at a differential to the market that reflects origin, grade, certification, and quality. This makes green coffee one of the very few agricultural commodities whose price a consumer might read about in a newspaper.

Essentially all of it is roasted for drinking, whether as roast and ground coffee or as the feedstock for soluble and instant manufacture, which draws heavily on robusta. Decaffeination is applied to green coffee before roasting and yields caffeine as a recovered by-product for other industries. The husks and hulls left at the dry mill are used locally for fuel, mulch, and — as cascara — a beverage in their own right.