Comparison of sensory attributes and chemical markers of the infrared spectrum between defective and non-defective Colombian coffee samples

Abstract

Defects in coffee affect the sensory quality of finished drink. To avoid this, defective beans are usually removed after threshing, as, once the green beans have been roasted, it becomes difficult to identify the defects. Procedures have been developed to evaluate coffee samples using infrared spectroscopy to detect such defects. As such, this study evaluated infrared spectra and sensory attributes of 39 coffee samples in: commercial ground and instant coffees, medium and high roast quality coffees, and defects present in the coffee. The sensory analysis was performed by 10 judges, semi-trained by a Q-grader, and eleven attributes were assessed using a semi-structured hedonic scale. The spectra obtained from the coffee samples were processed by mean centering, normalization (probabilistic quotient normalization), area normalization, first derivative and second derivative, later followed by principal component analyses. The sensory results showed differences in the evaluated attributes, differentiating between the samples of high quality medium roasted coffee from the other samples. After processing IR spectra of the samples by area normalization, PCA results exhibited four different groups: a) medium, high roasted quality coffee, with broken and chipped defects; b) commercial ground coffee and defects of sour, insect damaged, and faded; c) black defects, and d) instant coffee. Using the chemical descriptors obtained from the infrared spectra, it was possible to separate between high quality, commercial and instant coffee.

Physicochemical and sensory characteristics of dehydrated coffee pulp in function of drying temperature

“…The absorbance ranges reported by some authors for proteins are wavelength numbers 1,550-1,567 and 1,653 cm -1 , due to the flexion of NH in amide II and vibrations of NH 2 in amide I groups, respectively (Craig et al, 2014). In the 3,280 cm -1 range, attributed to water, drying at 50°C and 60°C showed absorbance values similar to those of the control treatment, which showed higher absorbance, indicating high water activity in this sample (Barrios-Rodríguez et al, 2020). Paradkar & Irudayaraj (2002) reported that the absorbance values related to the presence of caffeine in a product are the wavelength numbers 2,920 and 2,850 cm -1 , which have also been associated with the C-H bond vibration of the methyl group of the caffeine molecule (Craig et al, 2012).…”

“…A high contribution in the positive region for the wavelength of 1,450 cm -1 was observed, which is associated with the presence of chlorogenic acids pursuant to (Lyman et al, 2003) reports. Ranges of 1,381-1,376, 1,161-1,153, and 1,053 cm -1 could also be associated with chlorogenic acids (Barrios-Rodríguez et al, 2020). The wavelength range of 1,400-900 cm -1 is characterized by the vibrations of various types of bonds, including C=H, C=O, C=N, and P=O (Assis et al, 2019), both for PC1 and PC2, with high contributions from these wavelengths in the positive region.…”

“…A principal component analysis (PCA) was performed in ranges from 1,800-650 cm -1 , following the methodology used by Barrios-Rodríguez et al (2020), with a matrix of 9 × 155. Physicochemical and sensory results were analyzed using analysis of variance.…”

Denomination of origin ‘Café del Huila’ and dynamics of coffee growing in Colombia

“…Another important aspect related to the promotion of the quality of the coffee produced in the state of Huila, is the development of coffee quality competition events. In the case of the "Cup of excellence ® " contest (international contest also held in Colombia) among 11 versions carried out since 2003, the state of Huila is reported as the winner of five versions (2005, 2006, 2007, 2011 and 2013) (Bhumiratana;Adhikari;Chambers, 2011;Valencia;Pinzón;Gutiérrez, 2015;Barrios;Salas-Calderon;Giron-Hernandez, 2020). In addition to participating in international events where the quality of the crops is promoted, these spaces also attract direct markets, where the buyer and seller have an exchange of experiences on commercial agreements.…”

Llamado a realizar un adecuado uso de los subproductos del café

“…El proyecto se inició con la obtención de la materia prima en cereza de café, la cual fue lavada, seleccionada y despulpada. Para la evaluación se realizó un análisis de espectroscopia infrarroja por transformada de Fourier ATR-FTIR, ésta se realizó de acuerdo a la metodología empleada porBarrios et al 2020 y Guzmán et al. 2018, seguida por la cuantificación de ácido clorogénico y cafeína mediante cromatografía liquida, finalizando con la caracterización física y sensorial de la bebida, en la cual se determinaron parámetros como sólidos solubles, pH, acidez titulable (ICONTEC, 2004) y color; sensorialmente la bebida se evalúo con la participación de jueces semientrenados.…”