Reflectance methods can be divided into Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) and Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFTS). Even though both techniques have been recently employed for coffee analysis, most of the ATR-based studies used liquid samples (Gallignani, Torres, Ayala, & Brunetto, 2008; Garrigues, Bouhsain, Garrigues, & De La Guardia, 2000; Lyman, Benck, Dell, Merle, & Murray-Wijelath, 2003; Wang, Fu, & Lim, 2011; find more Wang & Lim, 2012), and thus would require an extra

extraction step in the analysis of roasted and ground coffee. However, ATR-FTIR can also be employed for analysis of solid samples and our previous studies comparing ATR-FTIR and DRIFTS

in the analysis of low and high quality coffees before roasting showed that, although both techniques were capable of discriminating see more between immature and mature coffees (Craig, Franca, & Oliveira, 2011), only DRIFTS could provide complete discrimination between non-defective (high quality) and defective (low quality) coffees (Craig, Franca, & Oliveira, 2012b). The previously mentioned studies showed that DRIFTS presented a more effective performance than ATR-FTIR in the discrimination between crude coffees of different qualities. Furthermore, DRIFTS was also shown to be appropriate for the analysis of roasted coffees, providing satisfactory discrimination between Arabica and Robusta varieties (Kemsley, Ruault, & Wilson, 1995; Suchánek, Filipová, Volka, Delgadillo, & Davies, 1996), between regular and decaffeinated coffees (Ribeiro, Salva, & Ferreira, 2010) and between

non-defective and defective coffees (Craig et al., 2012a). However, to the best of our knowledge, no attempts were reported in the literature on the use of this methodology for the analysis of adulteration of ground and roasted coffee samples, except for our preliminary study on the discrimination between roasted coffee, corn and coffee husks (Reis et al., 2013), Nintedanib ic50 in which the classification models developed were able to provide 100% discrimination between pure coffee, corn and coffee husks. The developed models were also able to discriminate between pure coffee and mixtures of coffee, corn and coffee husks, at adulteration levels of 10 g/100 g and above. Therefore, in the present study, we further evaluated this methodology by adding two more adulterants, i.e., spent coffee grounds and roasted barley, and decreasing the adulteration levels to 1 g/100 g, in order to confirm the potential of this technique for detection of multiple adulterants in roasted and ground coffee. Green Arabica coffee, barley and corn samples were acquired from local markets. Coffee husks were provided by Minas Gerais State Coffee Industry Union (Sindicafé-MG, Brazil).