Separation between high and low quality coffees by FTIR-ATR

The presence of defective coffee beans depreciates the quality of the coffee beverage consumed worldwide. The intrinsic defects (sour, black and immature beans) are the ones that, when roasted, contribute the most to the depreciation of the coffee beverage quality. Color sorting is the major procedure employed for separation of defective and non-defective coffee beans prior to roasting. However, such procedure is not efficient for separation of immature beans. Recent studies have shown that Fourier Transform Infrared Spectroscopy (FTIR) in combination with chemometric techniques have been successfully applied in the food industry for quality evaluation of food products. Thus, the objective of the present study was to evaluate the feasibility of employing FTIR for separation between high quality (non-defective) and low quality (defective) coffee beans. Defective (black, immature, light sour and dark sour) and non-defective Arabica coffee beans were manually separated. Ground coffee samples were then submitted to FTIR analysis employing an attenuated total reflectance (ATR) accessory. Multivariate statistical analysis (PCA and clusters) was performed in order to verify the possibility of discrimination between defective and non-defective coffee samples. The analysis was based on original spectral data and also on the first and second derivatives of the spectra. A clear separation between defective and non-defective coffee beans was observed, with the samples being distributed into three major groups: (i) non-defective, (ii) light sour and (iii) dark sour/black/immature. Such results indicate that FTIR analysis presents potential for the development of a fast and reliable analytical methodology for separation between high and low quality coffees.