However, no attempts were reported in the literature on the use of this methodology for the analysis of adulteration of ground and roasted coffee samples. Also, no reports were found on the analysis of coffee samples adulterated with more than one adulterant, be it with DRIFTS or any other analytical technique. Given the need for more effective and faster routine methods for analysis of coffee adulteration, the objective of this work was to evaluate the potential of DRIFTS for discrimination between roasted TAM Receptor inhibitor coffee and common adulterants such as roasted corn and coffee husks. Green Arabica coffee and corn samples were acquired from local markets.

Coffee husks were provided by Minas Gerais State Coffee Industry Union (Sindicato da Indústria de Café do Estado de Minas Gerais, Brazil). Coffee beans, coffee husks and corn samples (30 g) were submitted to roasting in a convection oven (Model 4201D Nova Ética, São Paulo, Brazil), at 200, 220, 240, 250 and 260 °C. After roasting, the samples were ground and sieved (0.39 mm < D < 0.5 mm) and submitted to color evaluation.

Color measurements were performed using a tristimulus colorimeter (HunterLab Colorflex 45/0 Spectrophotometer, Hunter Laboratories, VA, USA) with standard illumination D65 and colorimetric normal observer angle of 10°. Measurements were based on the phosphatase inhibitor library CIE L∗a∗b∗ three dimensional cartesian (xyz) color space represented by: Luminosity (L∗), ranging from 0 (black) to 100 (white) – z axis; parameter a∗, representing the green–red color component – x axis; and parameter b∗, representing the blue–yellow component -y axis. Previous studies have shown that roasting degree will be dependent on the type of sample and on the roasting temperature ( Franca, Oliveira, Oliveira, Mancha

Agresti, & Augusti, 2009; Oliveira et al., 2009). Preliminary tests showed that it would take temperatures higher than 240 °C to promote significant color changes in crude corn for it to be considered roasted to degrees comparable to those for commercially available coffee. Roasting of coffee husks, on the other hand, was only feasible for temperatures below 240 °C. Thus, for each sample type (e.g., coffee or adulterant), three temperatures were TCL selected in the range of 200–260 °C. For each temperature, several roasting times were tested. As expected, both increases in roasting temperatures and times led to decrease in luminosity (L*) values, e.g., darker roasts. In order to attain different levels of roasting (light, medium, dark) that could be representative of commercially available coffee, for each sample and temperature the roasting times were selected based on L* values measured for commercially available roasted coffee samples, corresponding to light (23.5 < L*< 25.0), medium (21.0 < L*< 23.5) and dark (19.0 < L*< 21.0) roasts.