Arabica Coffee Beans Research Articles

Which spectroscopic technique allows the best differentiation of coffee varieties: comparing principal component analysis using data derived from CD-, NMR- and IR-spectroscopies and LC-MS in the analysis of the chlorogenic acid fraction in green coffee beans

In this contribution we have analysed aqueous methanolic extracts of a total of 38 green bean coffee samples, which vary in terms of the coffee variety and processing conditions. We have characterised these extracts using NMR-, IR- and CD-spectroscopies along with LC-MS. All spectroscopic data have been analysed by principal component analysis (PCA) using different PCA processing parameters by an unsupervised non-targeted approach. We could show that the distinction between different groups of samples, in particular, Arabica versus Robusta green coffee beans can be successfully analysed by IR-spectroscopy and LC-MS. Surprisingly both CD- and NMR-spectroscopies fail to achieve, in this case, an adequate level of distinction. This is, to the best of our knowledge, the first study that directly compares the value of various spectroscopic techniques if multivariant statistical techniques are employed to them.

Application of EPR spectroscopy to the examination of pro-oxidant activity of coffee

Free radicals present in coffee may be responsible for exerting toxic effects on an organism. The objectives of this work were to compare free radicals properties and concentrations in different commercially available coffees, in solid and liquid states, and to determine the effect of roasting on the formation of free radicals in coffee beans of various origins. The free radicals content of 15 commercially available coffees (solid and liquid) was compared and the impact of processing examined using electron paramagnetic resonance (EPR) spectroscopy at X-band (9.3GHz). First derivative EPR spectra were measured at microwave power in the range of 0.7–70mW. The following parameters were calculated for EPR spectra: amplitude (A), integral intensity (I), and line-width (ΔBpp); g-Factor was obtained from resonance condition. Our study showed that free radicals exist in green coffee beans (1016spin/g), roasted coffee beans (1018spin/g), and in commercially available coffee (1017–1018spin/g). Free radical concentrations were higher in solid ground coffee than in instant or lyophilised coffee. Continuous microwave saturation indicated homogeneous broadening of EPR lines from solid and liquid commercial coffee samples as well as green and roasted coffee beans. Slow spin–lattice relaxation processes were found to be present in all coffee samples tested, solid and liquid commercial coffees as well as green and roasted coffee beans. Higher free radicals concentrations were obtained for both the green and roasted at 240°C coffee beans from Peru compared with those originating from Ethiopia, Brazil, India, or Colombia. Moreover, more free radicals occurred in Arabica coffee beans roasted at 240°C than Robusta. EPR spectroscopy is a useful method of examining free radicals in different types of coffee.

Strength of coffee beans under static and dynamic loading

Paper deals with experimental research on the crushing of coffee beans of different kinds under quasi-static and dynamic compression. The process of the crushing is described in details. It has been shown that there is variability in the crushing strength values. A relation between crushing strength and the coffee grain shape is also studied. Roasted Arabica coffee (Coffea arabica) beans were used for analyses. Arabica coffees were produced in different countries. All Arabica samples were submitted to a light roast. The detail analysis of the experimental data shows that there is no significant relation between parameters describing the fracture behaviour of the grains and grain geometry. These parameters are also independent on the grain weight. Compression of the coffee grains leads to their crushing. The fracture force is different for the different kinds of the coffee. The same is fact valid also for the strain at the fracture and for the energy absorbed during the grain crushing. Dynamic loading leads to the increase in the fracture force of coffee grains in comparison with the quasi static loading.

Antioxidant enzyme activity and hydrogen peroxide content during the drying of Arabica coffee beans

The development of the germination process and drought stress during the drying of coffee can generate reactive oxygen species, which can be neutralized by way of antioxidant mechanisms. No studies related to antioxidant enzymes during the drying of coffee were found in the literature, and considering their importance, the enzymatic activities of superoxide dismutase (SOD), guaiacol peroxidase (GPOX) and glutathione reductase (GR), and also the hydrogen peroxide content were evaluated during the drying of two types of coffee bean, one processed as natural coffee and the other as pulped natural coffee. The results showed a reduction in the SOD, GPOX and GR enzymatic activities of the natural coffee as compared to the pulped natural coffee during the drying period. Moreover, the hydrogen peroxide content of the natural coffee was greater than that of the pulped natural coffee. These results suggest the development of oxidative stress during the coffee drying process, controlled more efficiently in pulped natural coffee by the early action of GPOX during the drying process. Nevertheless, differential responses by SOD isoenzymes and possibly the role of other peroxidases also appear to be involved in the responses observed.

Karakteristik Fisik Bubuk Kopi Arabika Hasil Penggilingan Mekanis dengan Penambahan Jagung dan Beras Ketan

Size reduction applied on Arabica Coffee bean may change its physical properties, where these properties are utilized for designing process including packaging and appliances for further processes. This research aims to investigate physical characteristics of Arabica coffee powder with addition of corn and rice milled through mechanical process. This experiment used two mechanical mills including hammer mill and disc mill. Before it is milled, coffee was mixed with other materials including corn and rice. Parameters observed were yield, moisture content, bulk density, and angle of respose, particle uniformity index, fineness modulus, and the average particle dimensions. Based on the results obtained, it was revealed that moisture content of each test still meet SNI standard with the maximum of 7%. Bulk density of coffee powder resulted using disc mill was higher compared with hammer mill. However, particle generated from milling process may be categorized as powder with medium cohesiveness based on its angle of repose. Dimensional average particle is proportional to the fineness modulus of coffee powder produced. Highest fineness modulus obtained from coffee powder without additives, and using a hammer mill is equal to 4.37 with the highest average dimensions of 2.05 mm, while the lowest fineness modulus that the coffee powder without any additional ingredients milled with a hammer mill is equal to 4.22, with the lowest average dimensions of 1.94 mm.

Volatile composition and antioxidant capacity of Arabica coffee

This study compared the volatile and phenolic constituents of four Asian coffee varieties. The volatile components of Arabica coffee beans from Thailand (Doi Chang), Indonesia (Sidikalang and Sidikalang Kopi Luwak) and China (Yunnan) were extracted using dichloromethane and correlated with sensory data. The total concentrations of volatile compounds identified were 1239.04ppm (Yunnan), 1084.18ppm (Doi Chang), 1016.17ppm (Sidikalang) and 845.53 (Sidikalang Kopi Luwak). It was found that the Sidikalang Kopi Luwak coffee was most favourable with a well-balanced aromatic profile, though its overall profile was similar to that of Sidikalang. The Doi Chang and Yunnan coffees were perceived with distinctive sulphury notes mainly attributed to the sulphur-containing compounds of 8.32ppm and 12.63ppm, respectively. The phenolic compositions of the respective green and roasted coffee beans were also determined to assess their potential antioxidant activities. The total polyphenol content of the Sidikalang beans was the highest among the four coffee varieties. The antioxidant activities were measured using diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power assays (FRAP). Between the green and roasted coffee beans, the radical scavenging activity was similar, whereas the Arabica Sidikalang variety registered the highest ferric reducing capacity (p<0.05). Knowledge of the volatile composition and antioxidant capacities would facilitate a better understanding of Asian coffee quality.

Coffee origin discrimination by paper spray mass spectrometry and direct coffee spray analysis

Here we explore the application of the ambient ionization technique paper spray mass spectrometry (PS-MS) combined with the multivariate statistical tools principal component analysis and hierarchical cluster analysis as a fast and simple method to discriminate green arabica coffee beans from three different origins in Brazil. PS-MS does not require nebulizing gas or complex protocols for sample preparation and by the analysis of 5 μL of whole coffee bean extracts it was possible to discriminate the coffee origin. Furthermore, we report the direct analysis of a single coffee bean using a bean slice as the sample and also the substrate for electrospray ionization.

Analysis of luwak coffee volatile by using solid phase microextraction and gas chromatography (Analisa senyawa volatil kopi luwak dengan menggunakan mikroekstrasi fase padat dan kromatolgi gas).

The approach to authenticate Luwak coffee is made through analysis of volatile compounds of luwak coffee. Luwak coffee bean from type of arabica obtained from Andungsari Plantation in Bondowoso district, East Java Province Indonesia, was wet processed and sundried prior to roasting step. As many as 120 g green bean was roasted at 170-220°C for 8-12 minutes until reached light brown colour (Agtron scale 65) and was ground prior to extraction. Volatile compounds of roasted Luwak arabica coffee bean were extracted by using solid phase microextraction (SPME) at 60°C for 30 minutes. The extracted analyte was subsequently transferred into GC-FID system by splitless injection at 260°C with five minutes sampling time, continued with separation through 50% phenyl 50% dimethylpolysiloxane capillary column and oven temperature programmed from 60°C to 180°C with rate of 5°C/min. Resulted chromatogram shows major peaks mainly in Rt 8.360-9.981, and Rt 9.705-14.778, and minor peaks identified before Rt 10 and after Rt 24. Varied sample quantity ranged within 0.5-2.5 g produced chromatograms which were not significantly different (p=0.08). This research also observed the use of γ-picoline (4-methylpyridine) as internal standard. It was showed that γ-picoline appeared at Rt 8.6~ without overlaying other peaks originated from sample. Concentration of γ-picoline at 0.05 μL/g, resulted separable peaks. These findings showed that the use of solid phase microextraction and GC-FID is capable to be apply for identification and quantification of Luwak coffee

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.

Climatic factors directly impact the volatile organic compound fingerprint in green Arabica coffee bean as well as coffee beverage quality

Coffee grown at high elevations fetches a better price than that grown in lowland regions. This study was aimed at determining whether climatic conditions during bean development affected sensory perception of the coffee beverage and combinations of volatile compounds in green coffee. Green coffee samples from 16 plots representative of the broad range of climatic variations in Réunion Island were compared by sensory analysis. Volatiles were extracted by solid phase micro-extraction and the volatile compounds were analysed by GC–MS. The results revealed that, among the climatic factors, the mean air temperature during seed development greatly influenced the sensory profile. Positive quality attributes such as acidity, fruity character and flavour quality were correlated and typical of coffees produced at cool climates. Two volatile compounds (ethanal and acetone) were identified as indicators of these cool temperatures. Among detected volatiles, most of the alcohols, aldehydes, hydrocarbons and ketones appeared to be positively linked to elevated temperatures and high solar radiation, while the sensory profiles displayed major defects (i.e. green, earthy flavour). Two alcohols (butan-1,3-diol and butan-2,3-diol) were closely correlated with a reduction in aromatic quality, acidity and an increase in earthy and green flavours. We assumed that high temperatures induce accumulation of these compounds in green coffee, and would be detected as off-flavours, even after roasting. Climate change, which generally involves a substantial increase in average temperatures in mountainous tropical regions, could be expected to have a negative impact on coffee quality.

Biogenic Amine Profile in Unripe Arabica Coffee Beans Processed According to Dry and Wet Methods

Immature coffee fruit processing contributes to a high amount of defective beans, which determines a significant amount of low-quality coffee sold in the Brazilian internal market. Unripe bean processing was tested, taking the levels of bioactive amines as criteria for evaluating the extent of fermentation and establishing the differences between processing methods. The beans were processed by the dry method after being mechanically depulped immediately after harvest or after a 12 h resting period in a dry pile or immersed in water. Seven bioactive amines were quantified: putrescine, spermine, spermidine, serotonin, cadaverine, histamine, and tyramine, with global amounts ranging from 71.8 to 80.3 mg/kg. The levels of spermine and spermidine were lower in the unripe depulped coffee than in the natural coffee. The specific conditions of dry and wet processing also influenced cadaverine levels, and histamine was reduced in unripe depulped coffee. A resting period of 12 h does not induce significant alteration on the beans and can be improved if performed in water. These results confirm that peeling immature coffee can decrease fermentation processes while providing more uniform drying, thus reducing the number of defects and potentially increasing beverage quality.

Shape and Size Variability of Roasted Arabica Coffee Beans

Quantification and evaluation of selected Arabica (Coffea arabica L.) coffee beans' shape and size was performed. Twenty different coffee types originating from 13 different countries were analyzed. The main dimensions for individual coffee types were quantified. Sphericity, as a useful parameter for the calculation of processing and handling operations, was also quantified and ranged from 0.006536 to 0.009452. Calculation of shape variability using elliptic Fourier descriptors showed relevant differences among individual coffee samples. A dominant importance and the relevance of length-to-width ratio were quantitatively confirmed. A simple mathematical formula describing coffee grain contour was used with a satisfying correlation coefficient. Applicability of the approach was shown on the calculation of curvature radius.

Discrimination between defective and non-defective roasted coffees by diffuse reflectance infrared Fourier transform spectroscopy

The objective of this work was to evaluate the feasibility of employing Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) for discrimination between defective and non-defective coffees after roasting and grinding. Defective (black, immature and sour) and non-defective Arabica coffee beans were submitted to light, medium and dark roasts at 220, 235 and 250 °C. Principal Components Analysis of the DRIFTS spectra (normalized or not) and of the first derivatives of the spectra provided separation of the samples into four groups: non-defective, black, dark sour and light sour, with immature beans scattered among the sour samples. Classification models were developed based on Linear Discriminant Analysis and recognition and prediction abilities of these models ranged from 95 to 100%. Such results indicate that DRIFTS presents potential for the development of a fast and reliable analytical methodology for discrimination between defective and non-defective coffee after roasting and grinding.

Correlação entre precursores e voláteis em café arábica brasileiro processado pelas vias seca, semiúmida e úmida e discriminação através da análise por componentes principais

The influence of pre-processing of arabica coffee beans on the composition of volatile precursors including sugars, chlorogenic acids, phenolics, proteins, aminoacids, trigonelline and fatty acids was assessed and correlated with volatiles formed during roasting. Reducing sugars and free aminoacids were highest for natural coffees whereas total sugars, chlorogenic acids and trigonelline were highest for washed coffees. The highest correlation was observed for total phenolics and volatile phenolics (R= 0.999). Experimental data were evaluated by Principal Components Analysis and results showed that washed coffees formed a distinct group in relation to semi-washed and natural coffees.

Evaluation of the potential of FTIR and chemometrics for separation between defective and non-defective coffees

The objective of this work was to evaluate the potential of Fourier transform infrared spectroscopy (FTIR) for the discrimination of defective and non-defective coffee beans. Defective (black, immature and sour) and non-defective Arabica coffee beans were submitted to FTIR analysis by transmittance readings employing KBr discs and reflectance readings employing attenuated total reflectance (ATR) and diffuse reflectance (DR) accessories. Multivariate statistical analysis (PCA, clusters) was performed in order to verify the possibility of discrimination between defective and non-defective coffee samples. A clear separation between defective and non-defective coffee beans was observed, based on both PCA and cluster analysis of the reflectance spectra (ATR and DR accessories) and of the first derivatives of the transmittance spectra (KBr discs). Such results indicate that FTIR analysis has the potential for the development of a fast and reliable analytical methodology for the discrimination between defective and non-defective coffee beans.

Identification of nutritional descriptors of roasting intensity in beverages of Arabica and Robusta coffee beans

Arabica and Robusta coffee beans were roasted at 220 ± 10°C for 7, 9 and 11 min to identify chemical descriptors in the beverages. The pH of the beverages showed the lowest value in the medium roasting level. In each degree of browning, the soluble solids content remained slightly higher in Arabica drinks. The contents of caffeine did not vary, but trigonelline decreased with burning up intensity. Chlorogenic acids also decreased with increasing roasting time. The 5-O-caffeoylquinic acid prevailed in Arabica and Robusta beverages, but the isomers of dicaffeoylquinic and feruolilquínic acids remained higher in Robusta. It was concluded that trigonelline and total caffeoylquinic, fatty dicaffeoylquinic and fatty feruolilquínic acids detached the beverages according to roasting intensity. Caffeine and pH allowed drinks separation between both species. Soluble solids take apart Arabica and Robusta drinks in each degree of roasting. All the individual groups of chlorogenic acids also explained 90% of the variance among samples.

Discrimination between Immature and Mature Green Coffees by Attenuated Total Reflectance and Diffuse Reflectance Fourier Transform Infrared Spectroscopy

The objective of this work was to evaluate the potential of Fourier transform infrared spectroscopy (FTIR) in the characterization and discrimination between immature and mature or ripe coffee beans. Arabica coffee beans were submitted to FTIR analysis by reflectance readings employing attenuated total reflectance (ATR) and diffuse reflectance (DR) accessories. The obtained spectra were similar, but in general higher absorbance values were observed for nondefective beans in comparison to immature ones. Multivariate statistical analysis (principal component analysis, PCA, and agglomerative hierarchical clustering, AHC) was performed in order to verify the possibility of discrimination between immature and mature coffee samples. A clear separation between immature and mature coffees was observed based on AHC and PCA analyses of the normalized spectra obtained by employing both ATR and DR accessories. Linear discriminant analysis was employed for developing classification models, with recognition and prediction abilities of 100%. Such results showed that FTIR analysis presents potential for the development of a simple routine methodology for separation of immature and mature coffee beans. Practical Application: The ultimate goal of this research is to be able to propose improvements in the way immature coffee beans are separated from graded mature beans in coffee facilities (cooperatives and other coffee producer's associations). The results obtained herein point toward FTIR as a potential tool for the aimed improvements.

Effect of roasting conditions and grinding on free radical contents of coffee beans stored in air

The influence of roasting and storage conditions on free radical contents of individual Arabica coffee beans was examined during storage of whole, half and ground beans in air over a 1-month period. Free radical contents increased with increasing roasting time (roasting degree), but the atmosphere (air vs. N 2) used in the roasting and cooling process had little effect. There was a progressive increase in free radical contents with storage time, but the rate was much lower in whole beans than with half and fully ground beans, for which the rate was similar. These results suggest that exposure to O 2, rather than physical grinding is the main mechanism for storage-related free radical generation, and strongly indicate that roasted coffee is best kept as whole beans in order to minimise changes during prolonged periods of aerobic storage. Furthermore, they demonstrate that EPR measurements can contribute to understanding the process and storage related changes in coffee.

Effects of roasting degree on radical scavenging activity, phenolics and volatile compounds of Arabica coffee beans (Coffea arabica L. cv. Catimor)

We investigated the effect of roasting degree on volatile and phenolic compounds of coffee beans (Coffea Arabica L. cv. Catimor). The colour, 1,1-diphenyl-2-picrylhydrazyl radical-scavenging activity and phenolic acids of the aqueous extracts were studied. For the colour, L and b values were increased with an increase in roasting degree. Increasing roasting degrees led to a decrease in radical-scavenging activity. Maximum radical-scavenging activity was observed for the light-roasted coffee. Chlorogenic acid was the most predominant amongst the ten phenolic acids identified, in green and all roasted beans. Syringic acid, p-coumaric acid, gallic acid and sinapic acid increased with an increase in roasting degree. The volatile compounds were analysed using gas chromatography and mass spectroscopy. Aldehyde was the major volatile compound in green coffee. Our study has demonstrated that light-roasted coffee gave the most desirable quality of roasted coffee with respect to phenolic content and radical-scavenging activities.

Identification of chemical clusters discriminators of the roast degree in Arabica and Robusta coffee beans

To identify chemical parameters that might be used as discriminators, pH, soluble solids, caffeine, trigonelline, total caffeoylquinic acids, 3-O-caffeoylquinic acid, 4-O-caffeoylquinic acid, 5-O-caffeoylquinic acid, total dicaffeoylquinic acids, 3,4-O-dicaffeoylquinic acid, 3,5-O-dicaffeoylquinic acid, 4,5-O-dicaffeoylquinic acid, total feruloylquinic acids, 3-O-feruloylquinic acid, and 5-O-feruloylquinic acid were measured in Arabica and Robusta coffees submitted to three roasting levels. It was found that the fraction of soluble solids increased with roasting level, being slightly higher in Robusta roasted coffee. The contents of caffeine did not vary significantly between roasting degrees within the Arabica and Robusta samples, respectively, revealing a considerable stability during browning. The contents of trigonelline in Arabica and Robusta coffee decreased significantly with browning intensification. Overall, the levels of chlorogenic acids remained higher in Robusta roasted coffee beans but decreased sharply with roast increase. With roasting intensification, the ratio of total caffeoylquinic acids, total dicaffeoylquinic acids, and total feruloylquinic acids varied markedly in both species, with the proportion of total caffeoylquinic acids and total feruloylquinic acids increasing significantly, whereas the opposite occurred with dicaffeoylquinic acids. One can conclude, through the application of a multivariate analysis, that these chemicals form four clusters, constituting caffeine, trigonelline, total dicaffeoylquinic acids, and total feruloylquinic acids a relevant group for T3 roasting level discrimination, in both coffee species. Additionally, detailing discriminators for roasting intensity in Arabica coffee might be caffeine, trigonelline, 3-O-caffeoylquinic acid, and 4-O-caffeoylquinic acid, whereas in Robusta roasted coffee are trigonelline, 3-O-caffeoylquinic acid, 4-O-caffeoylquinic acid, 5-O-caffeoylquinic acid, 3,4-O-dicaffeoylquinic acid, 3,5-O-dicaffeoylquinic acid, 4,5-O-dicaffeoylquinic acid, 3-O-feruloylquinic acid, and 5-O-feruloylquinic acid.