Discrimination between roasted coffee, roasted corn and coffee husks by Diffuse Reflectance Infrared Fourier Transform Spectroscopy

Coffee 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.

► DRIFTS provided discrimination between roasted coffee and adulterated samples. ► Adulterants were roasted corn and coffee husks. ► Separation of coffee and adulterants based on raw or normalized spectra. ► Models classified samples as coffee (pure or adulterated), corn or coffee husks. ► Model recognition and prediction abilities were 100%.