Qualitative properties of roasting defect beans and development of its classification methods by hyperspectral imaging technology

•Roasting defect beans have its specific roasting degree with changes of quality properties.•Roasting defect beans can produce undesirable qualities of coffee brew.•Approximately 1420 nm was the most powerful wavelength to classify roasting defect beans.•Hyperspectral imaging technology can be used to classify various roasting defect beans.

Qualitative properties of roasting defect coffee beans and their classification methods were studied using hyperspectral imaging (HSI). The roasting defect beans were divided into 5 groups: medium roasting (Cont), under developed (RD-1), over roasting (RD-2), interior under developed (RD-3), and interior scorching (RD-4). The following qualitative properties were assayed: browning index (BI), moisture content (MC), chlorogenic acid (CA), trigonelline (TG), and caffeine (CF) content. Their HSI spectra (1000-1700 nm) were also analysed to develop the classification methods of roasting defect beans. RD-2 showed the highest BI and the lowest MC, CA, and TG content. The accuracy of classification model of partial least-squares discriminant was 86.2%. The most powerful wavelength to classify the defective beans was approximately 1420 nm (related to OH bond). The HSI reflectance values at 1420 nm showed similar tendency with MC, enabling the use of this technology to classify the roasting defect beans.