Quantitative evaluation of multiple adulterants in roasted coffee by Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) and chemometrics

Abstract

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.

Concomitant Use of Fourier Transform Infrared Attenuated Total Reflectance Spectroscopy and Chemometrics for Quantification of Multiple Adulterants in Roasted and Ground Coffee

“…The obtained RMSEC and RMSEP values were 1.44 and 2.42, respectively, and the correlation coefficient values of calibration ( ) and validation ( V ) were 0.99 for both parameters ( Table 2). It is noteworthy to mention that such model is more robust in comparison to the one obtained in our previous study [10] employing DRIFTS (LV = 10, RMSEC = 2.01, = 0.99, RMSEP = 3.70, and V = 0.96).…”

“…In order to develop analytical tools suitable to detect and identify adulteration in roasted and ground coffee, different techniques and procedures have been proposed, including UPLC [2], GC-MS [3], Direct Infusion Electrospray Ionization [5], HPAEC-PA [6], HPLC-DAD [7], UV-Vis, and Infrared Spectroscopy [4,[8][9][10][11]. Among these techniques, spectroscopic methods have gained attention in recent studies because they are fast, reliable, and simple to perform and usually do not require sample pretreatment, being thus appropriate for establishment of routine laboratory analysis.…”

“…In previous studies, we have shown that Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFTS) is suitable for identification, discrimination, and quantification of adulterants in roasted and ground coffee [4,9,10]. However, application of this method requires that the sample be mixed with KBr prior to analysis, and the amount employed for analysis is quite small, which could affect representativity, considering that adulterated coffee samples are inherently heterogeneous.…”

Fourier Transform Infrared and Raman and Hyperspectral Imaging Techniques for Quality Determinations of Powdery Foods: A Review

“…FT‐IR and Raman spectroscopic methods have been utilized to determine authenticity, microbes, and chemical compositions in cocoa and coffee powders. FT‐MIR spectroscopy has been employed to measure the fraudulent addition of multiple adulterants, including barley, corn, spent coffee grounds, and coffee husks in coffee powder (1% to 66% w/w), and to grade coffee powders into different quality levels (Briandet and others ; Wang and others ; Reis and others ). Very high accuracies were obtained by employing proper multivariate regressions (such as PLSR, PCR) and preprocessing methods (such as 1st Der, 2nd Der, SNV, and MSC) to build and enhance calibration models.…”

Diffuse reflectance Fourier transform infrared spectroscopy for simultaneous quantification of total phenolics and condensed tannins contained in grape seeds

“…Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) has been used for different quantitative determinations in food products (Pappas et al, 2011;Reis et al, 2013). One of the major advantages of spectroscopy is to collect information from a large sample area.…”