Effect of different extraction methods on the recovery of chlorogenic acids,caffeine and Maillard reaction products in coffee beans

Water and ethanolic extracts were obtained from green and roasted (3 different roast degrees) Arabica and Robusta coffee beans. Three types of water extracts were prepared from the examined, finely ground material through: (a) brewing with boiling water, (b) boiling in water, and (c) boiling in water under elevated pressure. All these extracts were lyophilized. Two types of ethanolic extracts were derived from the examined material through (a) extraction of the finely ground coffee beans and (b) extraction of the solid residue that remained after boiling the coffee beans in water under elevated pressure. These ethanolic extracts were dried. Both water and ethanolic extracts were analyzed for concentration of potential antioxidants such as chlorogenic acids and caffeine (by HPLC) and Maillard reaction products (measurements of absorbance at 420 nm). Concentration of chlorogenic acids in Robusta extracts varied between 0.4 and 36.0 g × 100 g⁻¹ dry extract weight (db.), while in Arabica extracts it ranged from 0.1 to 22.4 g × 100 g⁻¹ db. Extracts of dark roasted Arabica contained more chlorogenic acids than those of Robusta. Concentration of caffeine, which in green and roasted coffee beans is maintained at the similar level, tended to increase in Robusta extracts with the roast degree and temperature of extraction with water, while in case of Arabica extracts there was no noticeable tendency. Caffeine concentrations varied between 0.12 and 8.41 g × 100 g⁻¹ db. and between 0.03 and 6.53 g × 100 g⁻¹ db. in Robusta and Arabica extracts, respectively. Ethanolic extracts were characterized by relatively higher caffeine concentrations and lower contents of brown pigments and chlorogenic acids as compared to water extracts. The richest in antioxidants were extracts of green Robusta coffee beans derived through boiling in water under elevated pressure.     

Profiles of volatile compounds and sensory characteristics of Robusta coffee beans roasted by hot air and superheated steam

Although superheated steam (SHS) roasting has proved to be capable of improving selected quality of roasted Robusta coffee beans, impact of SHS roasting on aroma characteristics of the beans is not well understood. This study therefore aimed to investigate the effect of SHS roasting on aroma profiles and sensory characteristics of Robusta beans undergone SHS roasting at 190–250 °C; results were compared with those of beans roasted by hot air (HA). Sensory characteristics of selected samples were also compared with HA-roasted Arabica beans. Forty five aroma compounds were identified; most were fully developed in beans roasted at 230 °C and tended to degrade in beans roasted at 250 °C. SHS roasting led to more extensive formation of aroma compounds contributing to caramel note, while helped reduce formation of major contributors to spicy, roasty and burnt notes. SHS-roasted Robusta beans exhibited more resemblance to Arabica beans than their HA-roasted counterpart.     

Influence of coffee/water ratio on the final quality of espresso coffee

Espresso coffee is a polyphasic beverage in which the physico‐chemical and sensory characteristics obviously depend on both the selection of ground roasted coffee and the technical conditions of the percolation process. The aim of this work was to evaluate the influence of the coffee/water ratio on the physico‐chemical and sensory quality of espresso coffee. Furthermore, the influence of botanical varieties (Arabica and Robusta) and the type of roast (conventional and torrefacto) on the selection of coffee/water ratio was studied. The relationship between pH and the perception of acidity intensity is discussed in relation to the influence of the coffee/water ratio, type of coffee and roast. The optimisation of other technical parameters in previous studies seemed to minimise the influence of an increase in the coffee/water ratio on the extraction of soluble and solid compounds. In fact, only some sensory attributes, such as bitterness, astringency and burnt, acrid and earthy/musty flavours were proposed as relevant to the selection of 6.5 g 40 mL^?1 or 7.5 g 40 mL^?1 in conventional roasted coffees (Arabica 100% and Robusta blend), and 6.5 g 40 mL^?1 in torrefacto roasted coffees. On the other hand, the addition of sugar during the roasting process in torrefacto roast coffees seemed to contribute to a higher generation of acids, melanoidins and other compounds by the Maillard reaction or caramelisation, which led us to select the lowest coffee/water ratio. Copyright © 2006 Society of Chemical Industry     

Espresso coffee (EC) by POD: Study of thermal profile during extraction process and influence of water temperature on chemical–physical and sensorial properties

In this work the thermal profiles of five coffee pods (pure Arabica, pure Robusta, and Arabica Robusta blends: A20R80, A80R20, and A40R60) at 90, 100 and 110 °C are reported. Moreover the chemical–physical and sensorial properties of espresso coffee (EC) obtained from five different coffee pods were investigated. The analysis of the thermal profiles highlighted that the extraction process can be considered as an isothermal process because, after a starting phase, the recorded temperatures stayed around a mean temperature (T_m). In addition the T_m recorded for each extraction temperature was significantly lower than those set up by the controller. The chemical–physical parameters of EC samples increased proportionally with extraction temperature highlighting that the effectiveness of extraction process scales up with percolation temperature. The solid and caffeine contents of the EC samples extracted at 110 °C are related to an over extraction process. Principal Component Analysis (PCA) was applied to identify relationships and differences among EC samples. Pure Arabica and A80R20 EC samples at 100 and 110 °C have shown sensorial attributes typical for a fine espresso coffee.     

Optimization of espresso machine parameters through the analysis of coffee odorants by HS-SPME-GC/MS

The aroma profile and the final quality of espresso coffee (EC) are influenced by such technical conditions as the EC machine extraction temperature and the pressure used. The effect of these two parameters on EC quality were studied in combination by headspace solid phase micro extraction-gas chromatography-mass spectrometry (SPME-GC-MS) and sensory profile. Moreover, 10 key odorants at the best EC machine settings were examined to compare the two coffee cultivars (Arabica and Robusta) and two EC machines [Aurelia Competizione (A) and Leva Arduino (B)]. The data obtained provides important information about espresso making technique, suggesting that the usual espresso machine temperature and pressure settings (i.e. 92°C and 9bar) are very close to those needed to obtain the best quality espresso. This confirms the traditional wisdom of coffee making, which judges 25ml, the typical volume of a certified Italian EC, to be ideal for very strong aroma intensity.     

Changes on the levels of serotonin precursors – tryptophan and 5-hydroxytryptophan – during roasting of Arabica and Robusta coffee

The levels of free and total tryptophan and of 5-hydroxytryptophan (5-HTP) were investigated in green and roasted grains and beverages of Coffea arabica L. (Arabica) and Coffea canephora Pierre var. robusta (Robusta). Grains were light, medium and dark roasted. Free and protein tryptophan were extracted before and after hydrolysis. The levels of tryptophan and 5-HTP were quantified simultaneously by ion-pair HPLC and fluorimetric detection after derivatisation with o-phthalaldehyde. Robusta green coffee had higher total and protein tryptophan, whereas Arabica had higher free tryptophan levels. 5-HTP was not detected in the samples before and after roasting. Free tryptophan was completely degraded during roasting. Roasting significantly affected protein tryptophan. The rate of loss was smaller in Arabica compared to Robusta at every roasting degree. A beverage prepared the Brazilian way with a medium-roasted coffee provided 1.4–2.5 mg tryptophan/50 ml cup.     

A neuro‐fuzzy computational approach for multicriteria optimisation of the quality of espresso coffee by pod based on the extraction time,temperature and blend

We demonstrate how soft computing methods can be exploited to solve multicriteria quality optimisation problems in food science and technology. In particular, we link neuro‐fuzzy modelling techniques with simulated annealing to optimise/design the quality of espresso coffee by pod. The design variables are the extraction time (ranging from 10 to 30 s), temperature (80–110 °C) and blends (100% Arabica, 100% Robusta and Arabica Robusta: A20R80, A80R20 and A40R60); they are not the only variables that affect the sensory profile of a cup of espresso coffee, but have a strong impact on the sensory quality of the beverage. Based on the framework, we show that the particular problem is a nonlinear one. Hence, an espresso coffee characterised by a specific sensory profile can be extracted using different sets of parameter values. For example, the same sensory profile can be obtained using either pure Robusta extracted at 22 s and 94 °C or 90% Arabica and 10% Robusta extracted at 25 s and 99 °C. Yet, the global optimum with respect to the distance to the optimum sensorial values is obtained using 70% Arabica and 30% Robusta extracted at 15 s around 93 °C.     

Influence of extraction temperature on the final quality of espresso coffee

The final quality of espresso coffee (EC) depends upon certain technical conditions, such as the extraction temperature used in preparing it. The aim of this work was to investigate the effects of water temperature (88, 92, 96 and 98 °C) on the final quality of three types of EC (Arabica, Robusta Natural blend and Robusta Torrefacto blend) in order to select the optimal temperature. Volatile compound (analysed by Static headspace gas chromatography/mass spectrometry) and sensory flavour profiles were the most relevant parameters, whereas physicochemical, taste and mouthfeel parameters were not very useful for selecting the water temperature. For Arabica and Robusta Natural blend ECs, 92 °C was the optimal water temperature. For Robusta Torrefacto blend EC the overall acceptability might lead to the selection of 88 °C as the ideal water temperature, but the high percentages of key odorants related to roasty and earthy/musty flavours and the ‘not hot enough’ perception dictated the selection of 92 °C in this case as well. © 2003 Society of Chemical Industry     

Profiles of volatile compounds and sensory analysis of three blends of coffee: influence of different proportions of Arabica and Robusta and influence of roasting coffee with sugar

One hundred and forty‐six volatile compounds were identified and quantified using a static headspace sampler in three blends of coffee: Arabica/Robusta 80:20 (A80:R20) natural roasted coffee, Arabica/Robusta 20:80 (A20:R80) natural roasted coffee and Arabica/Robusta 20:80 with 50% of Robusta coffee roasted with sugar (A20:R80 50% Torrefacto). The different proportion of Arabica and Robusta coffee in the blend A80:R20 versus A20:R80 influenced the amounts of 20 chemical families of volatile compounds. Aldehydes, ketones, alcohols, pyrroles, pyrazines, furans, thiazoles, thiophenes, esters, oxazoles, lactones, sulphur compounds, pyridines, alkanes, alkenes, phenolic compounds, benzenic compounds, acids, pyranones and terpenes were present in higher quantities in the sample containing 80% of Arabica coffee, whereas sulphur compounds were more abundant in the coffee with 80% of Robusta. Sensory differences were also found between the two blends of coffee in the burnt, caramel, nutty, earthy and roasty notes. Torrefacto coffee, widely consumed in Spain, is obtained by roasting coffee with sugar. Higher quantities of ketones, alcohols, pyrazines, furans, pyridines, alkanes, phenolic compounds, pyranones and terpenes were found in the blend A20:R80 50% Torrefacto coffee versus A20:R80 natural roasted coffee. These differences in the volatile fraction were perceived by our panellists in the intensities of the nutty, roasty, earthy, burnt and caramel notes. © 2002 Society of Chemical Industry     

A study of the effect of roasting on the chlorogenic acid composition of coffee using HPLC

A method, based on HPLC, described in our previous publication for the analysis of chlorogenic acids in instant coffee, was used in a study of the effect of roasting on the chlorogenic acid composition of Arabica and Robusta coffee. The degradation of seven chlorogenic acids was followed during roasting. Losses of about 60% were observed when mild roasting conditions were used and almost 100% after severe roasting. Considerable differences in degradation rates of individual isomers were observed so that the composition of chlorogenic acids changed throughout the roasting process. Thus the degree of roasting may have a direct influence on the final product flavour as the individual isomers have different sensory properties.     

Discrimination between Arabica and Robusta green coffee using visible micro Raman spectroscopy and chemometric analysis

We have applied visible micro Raman spectroscopy combined with principal component analysis (PCA) as a powerful technique for the fast discrimination between the two coffee species, Arabica and Robusta, based on their chlorogenic acid (CGA) and lipid contents. The Raman spectra reveal different CGA and lipid compositions when comparing Arabica and Robusta green coffee. Analysing the whole Raman spectrum, the PCA yielded a clear separation between Arabica and Robusta with 93% of the total spectral variation. Here, the most significant spectral range lies between 1000 and 1750 cm⁻¹ and is dominated by the Raman bands of CGA. Also, by restricting the PCA analysis to the spectral range from 2700 to 3050 cm⁻¹, which is dominated by lipid bands, a reliable discrimination between the two coffee species could be achieved. In this case, the first two principal components of the PCA accounted for 85% of the explained total spectral variation.     

Peroxyl radical-scavenging activity of coffee brews

The ORAC_FL assay was used in non-automated mode to evaluate the specific peroxyl radical scavenging properties of the aqueous soluble components of green and roasted Arabica and Robusta coffee samples. A relationship between ORAC_FL and the concentration of CQAs (caffeoyl quinic acids) was found for the extracts from green coffee beans. Aqueous extracts from roasted coffee beans possessed equal or stronger scavenging power than that obtained for the green coffee beans extracts and the scavenging activity depended on the variety of coffee and the roasting conditions. Brews from Robusta coffee beans showed the highest ORAC_FL. The best scavenging properties for the brews from Arabica coffee beans were detected in samples prepared from coffee beans roasted under light conditions. The data indicate that, during roasting, a complex network of reactions takes place leading to the formation of a wide number of compounds possessing specific scavenging properties. Under mild roasting conditions, caffeoyl quinic acids appear to be the main components responsible for the free radical scavenging power of coffee brews. In contrast, Maillard reaction products may be the principal components with free radical scavenging activity in more severely (medium and dark) roasted coffees.     

Chemical characterisation of non-defective and defective green arabica and robusta coffees by electrospray ionization-mass spectrometry (ESI-MS)

The coffee roasted in Brazil is considered to be of low quality, due to the presence of defective coffee beans that depreciate the beverage quality. These beans, although being separated from the non-defective ones prior to roasting, are still commercialized in the coffee trading market. Thus, it was the aim of this work to verify the feasibility of employing ESI-MS to identify chemical characteristics that will allow the discrimination of Arabica and Robusta species and also of defective and non-defective coffees. Aqueous extracts of green (raw) defective and non-defective coffee beans were analyzed by direct infusion electrospray ionization mass spectrometry (ESI-MS) and this technique provided characteristic fingerprinting mass spectra that not only allowed for discrimination of species but also between defective and non-defective coffee beans. ESI-MS profiles in the positive mode (ESI(+)-MS) provided separation between defective and non-defective coffees within a given species, whereas ESI-MS profiles in the negative mode (ESI(−)-MS) provided separation between Arabica and Robusta coffees.     

DITERPENES AND DITERPENE ESTERS IN COFFEE

Coffee oil contains pentacyclic diterpenes as typical lipid constituents which have not been detected in any other foods. Major representatives are 16-O-methylcafestol, cafestol, and kahweol. Cafestol is contained in Arabica as well as in Robusta coffee. 16-O-Methylcafestol is found only in Robusta coffee. Larger quantities of kahweol were detected in Arabica coffee, but only trace amounts are present in Robusta.

In coffee oil, the diterpenes are hardly present in free form. They are largely esterified with fatty acids. Up to 14 fatty acid esters of 16-O-methylcafestol and cafestol have been identified. Palmitate followed by linoleate, oleate, stearate, arachidate, and behenate comprise almost 98% of the acid moieties. In Robusta coffee, the total amount of these six 16-O-methylcafestol esters are between 1.0 and 3.0 g/kg d.m. The contents of the corresponding cafestol esters vary between 2.0 and 8.0 g/kg d.m. in Robusta coffee and 9.0 and 22.0 g/kg d.m. in Arabica coffee.

Roasting has little influence on the percentage compositions of the diterpene ester fractions. Accordingly, the percentage distribution of diterpene esters in coffee powder is reflected in the resulting coffee brew. The absolute amounts depend on the type of preparation. In Scandinavian-type coffee, about 23% of the diterpene esters present in the powder can be found in the beverage. The lowest amount (0.3% of the initial quantity) is found in filtered coffee. An intermediate position is taken by espresso coffee with up to 2.5% of the initial concentration.     

DITERPENES AND DITERPENE ESTERS IN COFFEE

Coffee oil contains pentacyclic diterpenes as typical lipid constituents which have not been detected in any other foods. Major representatives are 16-O-methylcafestol, cafestol, and kahweol. Cafestol is contained in Arabica as well as in Robusta coffee. 16-O-Methylcafestol is found only in Robusta coffee. Larger quantities of kahweol were detected in Arabica coffee, but only trace amounts are present in Robusta.

In coffee oil, the diterpenes are hardly present in free form. They are largely esterified with fatty acids. Up to 14 fatty acid esters of 16-O-methylcafestol and cafestol have been identified. Palmitate followed by linoleate, oleate, stearate, arachidate, and behenate comprise almost 98% of the acid moieties. In Robusta coffee, the total amount of these six 16-O-methylcafestol esters are between 1.0 and 3.0 g/kg d.m. The contents of the corresponding cafestol esters vary between 2.0 and 8.0 g/kg d.m. in Robusta coffee and 9.0 and 22.0 g/kg d.m. in Arabica coffee.

Roasting has little influence on the percentage compositions of the diterpene ester fractions. Accordingly, the percentage distribution of diterpene esters in coffee powder is reflected in the resulting coffee brew. The absolute amounts depend on the type of preparation. In Scandinavian-type coffee, about 23% of the diterpene esters present in the powder can be found in the beverage. The lowest amount (0.3% of the initial quantity) is found in filtered coffee. An intermediate position is taken by espresso coffee with up to 2.5% of the initial concentration.     

Comparison of antioxidant and pro-oxidant activity in coffee beverages prepared with conventional and “Torrefacto” coffee

Antioxidant and pro-oxidant properties of coffee can be affected by several factors such as coffee variety, roasting process, storage, etc. The aim of this study was to compare the antioxidant and pro-oxidant properties of coffee beverages obtained with conventional and torrefacto roasted coffee.Coffee variety influences on the antioxidant capacity of ground coffee. A100 roasted samples presented lower antioxidant capacity than Robusta varieties. This could be due to the higher percentage of chlorogenic acids in Robusta ground coffee than in Arabica. Beside, A100 samples presented the highest value of pro-oxidant activity because these samples presented less efficient antioxidants.In Torrefacto roast, the antioxidant capacity increased and redox potential decreased due to the formation of MRPs, which have reducing properties.     

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.     

Roasted coffee oil microencapsulation by spray drying and complex coacervation techniques: Characteristics of the particles and sensory effect

The objective of this research was to microencapsulate roasted coffee oil using spray drying (SD) and complex coacervation (CC) techniques and to compare the microparticles properties and their sensory impact on the perception of soluble coffee brew aroma. Starch was used as wall material for spray dried microparticles (MSD), and gelatin and gum Arabic for that produced by complex coacervation (MCC). Ultrasound stable emulsions were obtained. Both microparticles presented a continuous wall and similar glass transition temperature (49.3 °C). MSD had 10.2% oil content and low surface oil content, and high solubility and wettability. MCC stood out for its high oil content (42.8%) and larger diameter (125 μm). Sensory evaluation showed that, when dissolved in hot water, microparticles provided a coffee aroma. Despite the MCC brew was preferred by assessors, the perception of coffee aroma intensity during the preparation of a soluble coffee brew containing MSD or MCC were similar.     

Authentication of Italian Espresso coffee blends through the GC peak ratio between kahweol and 16-O-methylcafestol

Since the price of Arabica is currently more than twice higher than Robusta, a rapid and reliable method for the determination of the roasted coffee blend composition is fundamental for the authentication of commercial blends used for the Italian Espresso coffee. A GC-FID method based on the ratio between the integrated peak areas of kahweol (K) divided by the sum of K and 16-O-methylcafestol (16MCF) was developed. No internal/external standard was used. Moreover, the quantitation of the unsaponifiable compounds is not necessary, as well as the calculation of any response factors. The percentage of Robusta in 34 samples of coffee blends with known composition, and in 48 samples of pure varieties was used to build a cubic polynomial function with R(2)=0.998. The roasting conditions did not affect the results. Considering eight commercial blends (ranging 0-90% Robusta), no significant difference (two-tailed P=0.817) was registered between the claimed and the predicted composition.