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

Abstract

This paper proposed the joint use of Fourier Transform Infrared Attenuated Total Reflectance Spectroscopy (FTIR-ATR) and Partial Least Square (PLS) regression for the simultaneous quantification of four adulterants (coffee husks, spent coffee grounds, barley, and corn) in roasted and ground coffee. Roasted coffee samples were intentionally blended with the adulterants, at adulteration levels ranging from 0.5 to 66% w/w. A robust methodology was implemented in which the identification of outliers was carried out. High correlation coefficients (0.99 for both calibration and validation) coupled with low degrees of error (0.69% for calibration; 2.00% for validation) confirmed that FTIR-ATR can be a valuable analytical tool for quantification of adulteration in roasted and ground coffee. This method is simple, fast, and reliable for the proposed purpose.

Combination of FTIR Spectroscopy and Chemometric Method on Quantitative Approach - A Review

“…0.69% and 2.00% for calibration and validation. The result confirms that the developed method using FTIR-ATR can be used as an important analytical device for quantitative analysis of adulteration present in roasted and ground coffee [49].…”

Mid-Infrared Spectroscopy as a Valuable Tool to Tackle Food Analysis: A Literature Review on Coffee, Dairies, Honey, Olive Oil and Wine

“…The proposed model provided reliable predictions of adulterations at levels as low as 1% w / w with determination coefficients of 0.99 and 0.98 for the calibration and validation sets, respectively [ 56 ]. In later studies, the same research group obtained similar results when assessed the performance of ATR for the same purpose, with the advantage that sample preparation was not necessary [ 54 ]. The two acquisition modes were compared using hierarchical models with two levels of PLS discriminant analysis [ 55 ].…”

Potential of Diffuse Reflectance Infrared Fourier Transform Spectroscopy and Chemometrics for Coffee Quality Evaluation

“…ATR collects information from the sample surface while DRIFTS provides information from the entire sample, being a combination of internal and external reflection [10]. Our previous studies have shown the feasibility of employing DRIFTS for detection of defective (low quality) coffee beans in admixtures with non-defective (high quality) ones [11] and also for detection and quantification of multiple adulterants in roasted and ground coffee [7]- [9]. In this study we extend our research by further evaluating the potential of this technique for discrimination between roasted coffees that presented distinct sensory characteristics under distinct roasting conditions.…”

“…Measurements were based on the 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. Discussion of color results will only take into account the luminosity parameter, given that previous studies on coffee analysis have established that this is the most relevant parameter for color evaluation [9], [12].…”

“…Over the last decades, the need for new and rapid analytical methods in the field of food analysis has prompted extensive research on spectroscopic methods, including Near Infrared Spectroscopy (NIRS) and Fourier Transform Infrared (FTIR) spectroscopy [1], [2]. Recent applications of such methods to coffee quality analysis include discrimination between Arabica and Robusta species [3], discrimination between defective and nondefective beans [4], [5] and discrimination between pure and adulterated coffee samples [6]- [9].…”