Drying and the Dry Mill

Why Drying Matters

After processing, coffee exists as parchment -- the bean wrapped in a thin papery hull. At this stage, moisture content is typically 45-55%. The goal of drying is to bring it down to 10-12% for safe storage without damaging the cellular structure that holds flavor compounds.

Dry too fast and the outer layers harden while the interior stays wet, creating conditions for mold. Dry too slowly and uncontrolled fermentation produces off-flavors. At our farms in Caicedonia, Valle del Cauca, we monitor moisture at every stage using calibrated moisture meters.

Drying Methods

We use two primary drying approaches across our 6 farms:

Raised Beds (Camas Africanas)

Raised beds allow air to circulate above and below the parchment. This is the gold standard for specialty coffee drying.

• Layer thickness -- coffee is spread 2-4cm deep
• Turning frequency -- every 30-45 minutes during the first 2 days, then every 2-3 hours
• Duration -- typically 10-18 days depending on weather and process method
• Advantage -- even drying, excellent air circulation, reduced mold risk

Mechanical Dryers (Silos)

When rain threatens or volume exceeds bed capacity, mechanical dryers provide a controlled alternative.

• Temperature -- never above 40-45 degrees Celsius to protect flavor compounds
• Airflow -- continuous, gentle forced air
• Duration -- 24-48 hours to finish drying
• Common practice -- pre-dry on beds for 2-3 days, then finish in the silo

The Critical Moisture Window

Moisture content determines everything about storage stability and export readiness:

• Above 12% -- risk of mold, fermentation, and rapid quality degradation
• 10-12% -- safe zone for storage (up to 6 months in proper conditions)
• Below 10% -- the bean becomes brittle, loses flavor compounds, and can develop "baggy" or woody flavors
• Export standard -- most buyers require 10.5-11.5% moisture on arrival

We track humidity readings for every lot to ensure compliance before any coffee leaves our warehouse.

The Dry Mill: From Parchment to Green

Once parchment coffee is properly dried and rested (ideally 30-60 days in reposo), it moves to the trilladora (dry mill) for final preparation:

1. Hulling (trilla) -- mechanical removal of the parchment layer to reveal the green bean

2. Density sorting -- vibrating tables or air columns separate beans by weight, removing lights (underdeveloped beans)

3. Screen sizing -- beans are separated by physical size through calibrated screens

4. Color sorting -- optical machines or hand sorting removes defective beans (blacks, sours, broken)

5. Grading -- the final lot is assigned a screen size, defect count, and preparation grade

Our Dry Mill Inventory

At Particular Coffee, our dry mill currently holds 219 lots of green coffee at various stages of preparation. Each lot carries full traceability: farm, plot, variety, process method, harvest date, and SCA score. This level of detail is what allows us to offer buyers transparency from seed to shipment.

Pretrilla Analysis

Before hulling, we perform a pretrilla analysis -- cracking open a sample of parchment to inspect the green bean inside. This reveals defects like broca damage, immature beans, and physical deformities that are invisible through the parchment layer. It is our last quality gate before committing a lot to the milling process.

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This post is adapted from Module 6 of our Seed to Cup course. Want to see real pretrilla analysis data from our lots? Join our free community at [skool.com/particular-3064](https://skool.com/particular-3064) for behind-the-scenes content from the dry mill.