Separation between high and low quality coffees by FTIR-ATR

摘要

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 tothe depreciation of the coffee beverage quality. Color sorting is the major procedure employed for separationof defective and non-defective coffee beans prior to roasting. However, such procedure is not efficient forseparation 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 forquality evaluation of food products. Thus, the objective of the present study was to evaluate the feasibility ofemploying FTIR for separation between high quality (non-defective) and low quality (defective) coffeebeans. Defective (black, immature, light sour and dark sour) and non-defective Arabica coffee beans weremanually separated. Ground coffee samples were then submitted to FTIR analysis employing an attenuatedtotal reflectance (ATR) accessory. Multivariate statistical analysis (PCA and clusters) was performed in orderto verify the possibility of discrimination between defective and non-defective coffee samples. The analysiswas based on original spectral data and also on the first and second derivatives of the spectra. A clearseparation between defective and non-defective coffee beans was observed, with the samples beingdistributed into three major groups: (i) non-defective, (ii) light sour and (iii) dark sour/black/immature. Suchresults indicate that FTIR analysis presents potential for the development of a fast and reliable analyticalmethodology for separation between high and low quality coffees.