Fractality in coffee bean surface for roasting process

The roasting is the stage where the coffee bean undergoes physiochemical changes that provide their typical sensory characteristics (i.e., aroma and flavor). Despite the importance, the roasting process is performed based on the operator experience, which makes difficult the homogenization between batches of roasted coffee. In that sense, this paper proposes a methodology to analyze changes in the coffee bean during roasting; this can be used as an indicator of the roasting degree. The proposal is based on R/S fractal analysis of coffee bean surface images taken during the roasting process. The results indicate that the Hurst exponent exhibits dynamic changes that can be correlated with the physical changes of the coffee bean, such as fractures and color changes, suggesting that the fractal index could be used for indirect monitoring of the roasting degree.