Coffea arabica beans microstructural changes induced by roasting: An X-ray microtomographic investigation

The present work reports on a microstructural characterization of Coffea arabica beans in the course of roasting by means of X-ray microtomography technique (μCT). In fact, the aim of this study is to demonstrate the capability of μCT as a useful tool for the characterization of microstructure of C. arabica beans at different roasting times: from green to very dark. μCT is a non-invasive technique that has the ability to image low moisture materials by using the differences in X-ray attenuation arising, mainly, from differences in density within the specimen. Green coffee beans were roasted and sampled at the following roasting times; 2, 3, 4 and 5 min. Several parameters such as percentage object volume (POV), density, total volume and pore size distributions were calculated for each roasting time and their variations discussed. The results from this study show how the microstructure of the coffee bean evolves with increasing roasting time, for example, the increase in total pore volume, the increase in porosity and density due to the rupture of bonds in the internal structure of the coffee beans during roasting. μCT has proven to be a suitable technique for microstructural analysis of roasted foods such as coffee bean and provides an accurate analysis of the pores and microstructure during the roasting process.