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a b s t r a c tCoffee has been the target of fraudulent admixtures with cheaper materials, including coffee husks and other roasted grains. Given the successful application of spectroscopic methods in the field of food adulteration as fast and reliable routine techniques, the objective of this work was to evaluate the feasibility of employing Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) for discrimination between roasted coffee and common adulterants (roasted corn and coffee husks). Arabica coffee beans, coffee husks and ground corn kernels were submitted to light, medium and dark roasts at temperatures ranging from 200 to 260 C. Principal Components Analysis of the DRIFTS spectra provided separation of the samples into three groups: coffee, coffee husks and corn. Classification models were developed based on Linear Discriminant Analysis, and such models provided complete discrimination (100% recognition and prediction) between roasted coffee, pure adulterants (corn and coffee husks) and adulterated coffee samples. Such results indicate that DRIFTS can be employed for discrimination between coffee and its common adulterants.

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The current study presents an application of Diffuse Reflectance Infrared Fourier Transform Spectroscopy for detection and quantification of fraudulent addition of commonly employed adulterants (spent coffee grounds, coffee husks, roasted corn and roasted barley) to roasted and ground coffee. Roasted coffee samples were intentionally blended with the adulterants (pure and mixed), with total adulteration levels ranging from 1% to 66% w/w. Partial Least Squares Regression (PLS) was used to relate the processed spectra to the mass fraction of adulterants and the model obtained provided reliable predictions of adulterations at levels as low as 1% w/w. A robust methodology was implemented that included the detection of outliers. High correlation coefficients (0.99 for calibration; 0.98 for validation) coupled with low degrees of error (1.23% for calibration; 2.67% for validation) confirmed that DRIFTS can be a valuable analytical tool for detection and quantification of adulteration in ground, roasted coffee.

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