Buyer Education

How to Read a Green Coffee Spec Sheet

A spec sheet tells you more about a coffee than any marketing copy. Once you know what the numbers mean, you can make better buying decisions—and ask better questions when something's missing.

By Samuel Demisse — 3× U.S. Coffee Tasters Champion, Q-Grader, 34 years in specialty coffee

Overview

What a good spec sheet includes

Origin info

  • • Country
  • • Region
  • • Producer/station
  • • Elevation
  • • Variety

Processing

  • • Process method
  • • Fermentation details
  • • Drying method
  • • Crop year
  • • Harvest dates

Quality specs

  • • Moisture %
  • • Water activity (aW)
  • • Density (g/L)
  • • Screen size
  • • Defect count

Cupping

  • • Cupping score
  • • Flavor notes
  • • Acidity descriptor
  • • Body descriptor
  • • Cupper/Q-grader

Spec #1

Moisture content (%)

Moisture tells you how much water is in the bean. It affects roast behavior, storage stability, and whether you're paying for water weight.

Target range: 10–12% is ideal. Above 12% = storage risk. Below 9% = likely faded or past-crop.
Roast impact: Higher moisture = slower heat transfer. Wetter beans need more energy to reach first crack.
What to ask: "When was this measured?" Moisture at origin vs arrival can differ.

Reading moisture

Below 9% Risk: faded cup
9–10% Acceptable (watch freshness)
10–12% Ideal range
Above 12% Risk: mold, instability

Spec #2

Water activity (aW)

Water activity measures how "available" the moisture is for microbial growth. It's a better predictor of shelf stability than moisture content alone.

Target range: 0.50–0.60 aW is ideal for stability. Below 0.50 = very dry. Above 0.60 = watch carefully.
Why it matters: Mold needs aW > 0.70 to grow. But coffee fades before mold—flavor drift happens earlier.
For naturals: Lower aW (0.50–0.55) helps naturals stay stable longer since they're more prone to flavor drift.

Reading water activity

Below 0.45 Very dry (possibly over-dried)
0.50–0.60 Ideal range
0.60–0.65 Acceptable (monitor storage)
Above 0.65 Risk: accelerated aging

Specs #3 & #4

Density and screen size

Density (g/L)

Higher density often correlates with higher elevation, slower maturation, and more complex cup. Denser beans absorb heat differently.

  • 600–650 g/L: Lower density. Often lower elevation.
  • 650–700 g/L: Medium density. Common range.
  • 700–750+ g/L: High density. Often high elevation, complex cup.

Screen size

Screen size measures bean dimensions. Larger screens (17/18) are often premium-priced. But size ≠ quality—it's about uniformity for even roasting.

  • Screen 13–14: Smaller. Common in some origins.
  • Screen 15–16: Medium. Most specialty falls here.
  • Screen 17–18+: Large. "Supremo" or "AA" grades.

Roast implication: Uniform screen size = even heat absorption = consistent development. Mixed sizes mean some beans are done before others.

Spec #5

Cupping score

The SCA cupping score is the most-cited quality number. It's useful for screening, but it's not the whole story.

Score ranges

80–84 Very Good
85–89 Excellent
90+ Outstanding

What affects score

  • • Fragrance/Aroma
  • • Flavor
  • • Aftertaste
  • • Acidity
  • • Body
  • • Balance
  • • Uniformity
  • • Clean cup
  • • Sweetness

Score caveats

  • Different cuppers score differently
  • Origin cupping ≠ arrival cupping
  • Light roast sample ≠ your roast
  • Score inflation is real
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