Coffee Cherries

A coffee cherry has a skin, a layer of sweet pulp, a slippery mucilage layer, a papery parchment, and a thin silverskin, all wrapped around the seeds. Every one of those layers has to be removed before there is a coffee bean to trade, and the differences between coffee processing methods are differences in when and how they come off. The cherry, in other words, is the raw material of an operation, and it is bought as such.

The trade in cherries is local by necessity. Smallholders deliver the day's picking to a wet mill or a collection station within a short distance and are paid on weight and on a visual assessment of ripeness. Estates process their own. Nothing about this trade crosses a border, because nothing in it could survive the journey — which is precisely why coffee cherries and green coffee are two different commodities and not two views of the same one.

Coffee ripens unevenly. A single branch carries green, ripening, ripe, and overripe cherries at the same time, and the tree keeps producing through a harvest that runs for weeks or months. This is why fine coffee is picked selectively by hand, pass after pass, taking only the ripe cherries and returning days later for the next — a labour-intensive process that is the largest single cost in producing quality coffee.

The alternative is strip picking, taking everything from the branch in one pass, which is faster and cheaper and delivers a mixed lot. Underripe cherries yield beans that taste grassy and astringent; overripe and dried cherries contribute fermented and mouldy flavours. Because the seed inside develops with the fruit, ripeness at picking sets a ceiling on the cup quality that no amount of skilled processing or careful roasting will lift.

Once picked, the cherry is on a clock. Its pulp is sugary and its skin is broken easily by handling, and at ambient tropical temperature microbial activity begins within hours. Cherries left heaped in sacks heat internally, ferment unevenly, and develop off flavours that pass into the seed. Delivery to the mill on the day of picking is therefore not a best practice but the basic requirement of the commodity, and the geography of coffee processing — mills scattered close to the farms rather than centralised — exists because of it.

At the mill, cherries are usually floated in water as the first sorting step: ripe, dense cherries sink while underripe, dried, and insect-damaged ones float and are separated off. This simple density separation is one of the most effective quality interventions in the whole chain, and it is possible only because the lot is still fresh.

Two broad routes lead from cherry to green coffee, and the choice is one of the defining decisions of the coffee world. In the washed or wet route, the skin and pulp are stripped from the cherry mechanically within hours, the mucilage is removed by fermentation or friction, and the parchment-covered bean is dried. In the natural or dry route, the whole cherry is dried intact, fruit and all, and the dried layers are hulled off afterwards.

The routes are not interchangeable, and they impose different demands on the cherry. Wet processing requires water, infrastructure, and speed, and it is unforgiving of unripe fruit — but it delivers a cleaner, more consistent bean. Dry processing needs little equipment but a long spell of dry weather and a great deal of turning and attention, since a thick fruit layer dried badly moulds. Honey and pulped-natural routes sit between them, removing skin but leaving some mucilage to dry on the bean.

• Washed (wet) — skin and pulp removed immediately, mucilage removed, bean dried in parchment
• Natural (dry) — the whole cherry dried intact and hulled afterwards
• Honey and pulped-natural — skin removed, some mucilage left to dry on the bean

Cherry lots are assessed on the proportion of ripe fruit, freedom from foreign matter and debris, and the absence of overripe, dried, and damaged cherries. Because payment at collection is usually on weight with a ripeness assessment, the incentives in a cherry trade are worth understanding: a system that pays on weight alone rewards volume over selectivity, and cherry pricing structures are one of the levers producing countries use to influence coffee quality.

• Underripe green cherries, yielding astringent, grassy beans
• Overripe and dried cherries picked from the branch or the ground
• Fermentation damage from cherries held too long before processing
• Insect damage, notably from the coffee berry borer
• Foreign matter — leaves, twigs, and stones in the delivered lot
• Crushed and split cherries from rough handling in transport