Roasting green coffee beans using spouted bed roaster: changes in physical characteristics

Area of Science:

• Food Science
• Agricultural Engineering

Background:

• Green coffee beans (Coffea arabica) undergo significant physical and chemical changes during roasting.
• Spouted bed roasting offers potential advantages for coffee processing due to efficient heat and mass transfer.

Purpose of the Study:

• To investigate the impact of spouted bed roasting parameters on the instrumental color and texture of pea-berry grade green coffee beans.
• To determine optimal roasting conditions balancing desirable color attributes and reduced bean fracture force.

Main Methods:

• Pea-berry grade green coffee beans were roasted using a laboratory model spouted bed roaster.
• Roasting was performed at varying temperatures (150-250°C) and times (30-300 seconds).
• Instrumental color (hue, chroma, brightness) and texture (maximum force) were analyzed.

Main Results:

• Roasting significantly decreased bean brightness, with time being a major factor.
• Chroma decreased curvilinearly with increased roasting time and temperature.
• Hue (dominant wavelength) increased from 576 to 603 nm.
• Maximum force, indicating bean texture, decreased with higher roasting temperatures and longer times.

Conclusions:

• Spouted bed roasting parameters critically influence coffee bean color and texture.
• Optimal roasting conditions were identified to achieve desirable color profiles and reduced bean fracture force, crucial for processing and quality.