Pore structure of coffee beans affected by roasting conditions

Hot-air roasting of coffee beans not only forms color and flavor compounds but also leads to a complete alteration of the bean microstructure. The res ulting pore structure controls mass transfer phenomena during roasting and storage. The principal objective of the present project was to investigate the influence of different roasting conditions on volume increase and pore- structure development. Coffee beans were roasted in 2 different, well-defin ed roasting processes to equal degree of roast. Volumetry, mercury porosime try, and electron microscopy were employed to study structural product prop erties. The roasting conditions were found to have a major impact on micros tructure. High-temperature roasted coffees had greater bean volume, pore vo lume and larger micropores in the cell walls as compared to low-temperature roasted beans.