From farm to roaster

Dry it, then leave it alone

Fresh off the tree, coffee is about 60% water, give or take. Drying takes it to about 10–12%, where mold can’t get going. Stop early and it spoils; go below about 9% and the beans shrink and crack, and sell short: coffee is sold by weight.

The dry mill

The dried coffee rests in its parchment a month or two, then hullers crack it off — or the whole dried husk of a natural — to leave green coffee. Some mills polish off the thin silver skin too.

How a mill sorts

Put the mill’s sorts in the order they happen.

1. Through perforated screens
2. Over shaking tables
3. Past a color sorter
4. By hand

Size first, through perforated screens, then weight on shaking tables, then color, and finally by hand, which is still the fussiest machine in the building.

Screens and grades

Screens are sized in 64ths of an inch, so a bean held by screen 18 is about 7 mm across. Kenya’s AA means big beans, roughly screens 17–18; India’s Extra Bold (EB), screen 19 and up. Both are sizes, not promises of flavor.

The only child

Now and then a cherry grows one round seed instead of two flat-faced ones. That’s a peaberry, a small share of any crop (around 5% is often quoted), sieved out and sold as PB.

What makes it specialty

A grader picks through a few hundred grams of green coffee for black or sour beans, insect damage, stones and sticks. Specialty grade allows no serious defects, a handful of minor ones, and a cup that stands out.

86 points

For decades specialty also meant a score of 80 or more on the SCA’s 100-point form. Its newer system leans on descriptions over a single cut-off, but “86 points” lingers on bags like an old habit.

A bag says “86 points”. That number is…

Answer: A grader’s considered opinion, scored on a 100-point form. The old specialty line was 80, and the cup must still stand out.

What a mark promises

Sort each mark on a bag by what it actually promises.

• Bean size
  • Kenya AA
  • Mysore Nuggets EB
  • PB
  • Screens 17–18
• Cup quality
  • 86 points
  • Specialty grade
  • No serious defects

Size grades say how big the beans are, and even sizing helps an even roast. A score or a grade is about the cup, and about what the grader did not find in it.

Sacks, ships and shelf life

Green coffee travels in jute sacks, counted by the trade in 60 kg bags, often with a sealed liner to hold the moisture steady. Well dried and well stored, it tastes fresh for about a year. Green coffee is the patient stage.

Past crop

Green coffee a year or two past harvest tends to taste…

Answer: Papery and woody — what buyers call past crop. Green coffee holds up for about a year, where roasted coffee fades in weeks.