Quality Metric
Water Activity (aW)
A measure of how available water is for microbial growth and chemical reactions. Predicts shelf stability better than moisture content alone. The spec most buyers skip but shouldn't.
Definition
What water activity measures
Water activity (aW) is the ratio of vapor pressure in coffee to vapor pressure of pure water. It ranges from 0.00 (bone dry) to 1.00 (pure water). It tells you how "available" water is--not just how much is present.
Water bound to sugars and proteins behaves differently than free water. Two coffees can have the same moisture percentage but different water activity--and behave very differently in storage.
Key numbers
Why Roasters Care
What water activity tells you
Shelf life prediction
Below 0.60 aW, most microorganisms can't grow. This is a well-established threshold in food science. Coffee stored below this line is stable.
Roast consistency
Water activity affects how beans absorb heat. Consistent aW means more predictable roast development batch to batch.
Quality indicator
High aW can indicate rushed drying, poor storage, or processing problems. It's a red flag worth investigating before buying.
Our Approach
How we use water activity
Check at origin
We measure aW before committing to purchase. High readings mean something went wrong in processing.
Re-measure on arrival
aW can change during ocean transit if moisture barrier fails. We verify before offering to customers.
Provide on spec sheets
Every lot we sell includes water activity data. You shouldn't have to ask for this basic spec.
Lower targets for naturals
Natural process coffees are more sensitive. We target 0.50-0.55 for naturals to preserve fruit character.
Current Inventory
Coffees with water activity data
Natural Sidama American Decaf
Oromia, Sama
Crisp Apple | Toasted Almond
UVVW · In Stock
SWD Natural Sidama
Oromia, Sama
Hint of fruit, Apple | Sweet
SWD · In Stock
WUSH WUSH
Oromia, Hambela
Sangaria | Fruit Bomb | Floral | Sweet Finish
Natural, 120 hours dry Fermentation! · In Stock
Harrar Gr 1
Oromia, Micheta
Chocolate | Barries | Carmel | Full Body
Natural · In Stock
Washed GUJI
Oromia, Bensa
Black Tea | Floral | Bergamot
Fully washed · In Stock
Natural ARDI
Sidama, Damo
Clean Strawberry | Peach | Sweet Finish
Natural · In Stock
Deep Dive
Water Activity in Green Coffee
Why water activity matters more than moisture for shelf life, and ideal ranges by process.
Related Terms
More Quality Metrics
Moisture Content
Percentage of water in green coffee. Target 10-12% for stability.
Density
Bean mass per volume. Affects heat transfer and roast development.
Q Score
Cupping score from a certified Q-grader. 80+ is specialty grade.
Q Grader
Licensed coffee professional certified by CQI to evaluate specialty coffee.
Defects
Physical or sensory flaws that reduce coffee quality and grade.
Screen Size
Bean size measured by round-hole screens. Larger = more uniform roasts.
Want the full spec sheet?
We provide water activity, moisture, density, and cupping scores on every lot.