Research Module

Water Activity

The most underrated indicator in specialty coffee

Moisture tells you how much water there is. Water activity tells you what that water will do to your coffee. aW measures how much of that water is free — and only free water participates in reactions and microbial growth. It's the difference between an inventory and a behavior.

Reference Parameters

Zona segura

<0.60

Zona atenção

0.60-0.70

Zona crítica

>0.70

Linha vermelha

0.70aW

Ideal

0.50-0.60aW

Interactive Chart

* Reference data. Real experiments will be published soon.

Reference Values

aW < 0.50: Very dry — risk of sensory loss

aW 0.50-0.60: Ideal — maximum stability, long shelf life

aW 0.60-0.70: Acceptable with constant monitoring

aW > 0.70: Critical — fungal growth, ochratoxin A possible

aW > 0.80: Bacteria proliferate — coffee compromised

Two lots with 11% moisture can have opposite fates: aW 0.55 = stable | aW 0.72 = unstable

aW is born in drying: homogeneous drying = stable aW; rushed drying = surface seals → free water trapped → unstable aW

Free water accelerates: lipid oxidation, enzymatic reactions and premature Maillard

Measurement: bean sealed in chamber until thermodynamic equilibrium. Equilibrium RH ÷ 100 = aW

Planned Experiments

Study #006

Aw x packaging type correlation over 6 months

Coming soon

Study #011

Comparison: same lot, same moisture, different aW — opposite fates

Coming soon

Study #012

Impact of drying speed on final aW

Coming soon

Want to participate?

If you're a producer and want your coffee to be part of our studies, get in touch.

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