Green Coffee Moisture Content & Bulk Density: Adjusting Charge Temps & Heat Input

Pre-roast laboratory measurement guidelines: adjusting charge temperature, soak duration, and burner power for high-density Kenya SL28 vs low-density Brazil Cerrado.

Why Roasting Green Coffee Blind Leads to Inconsistency

No two bags of specialty green coffee absorb heat identically. Roasters who use the same charge temperature across all origins will either scorch low-density beans or stall the drying phase on dense high-elevation lots.

Before dropping a green batch into an RC-Tech roaster, two physical parameters must be quantified: Free Moisture Content (%) and Bulk Density (g/L).

1. Water Activity & Moisture Content - Ideal Range: 10.0% to 11.5% moisture content. - High Moisture (11.5%+): Demands higher convective airflow and a longer drying phase to evacuate free water without creating a sudden thermal crash. - Low Moisture (Under 9.5%): Vulnerable to fast heat absorption. Reduce charge temperature by 10°C–15°C to avoid scorching brittle outer layers.

2. Bulk Density (Specific Gravity) - High Density (Above 700 g/L - e.g., Kenya, Ethiopia washed at 2,000m): Cellular structure is compact with microscopic air pockets. Requires high charge temperature (205°C–215°C) and strong convective heat to conduct thermal energy all the way to the bean embryo. - Low Density (Under 640 g/L - e.g., Brazil natural, lower-altitude washed): Porous cellulose structure conducts heat rapidly. Use a gentler charge temperature (180°C–190°C) with slower initial heat application to avoid internal tipping defects.

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