Roast Degree Research Articles

コーヒー豆中のクロロゲン酸類と総ポリフェノールの分析

The behavior of the chlorogenic acids (CGAs) and total polyphenols by the difference in roast degree of coffee beans was investigated. As samples, Coffea robusta and Coffea arabica from Brazil, six kinds of different roast degree beans and green beans, were used. HPLC/UV was used for the measurement of CGAs. LC separation was performed on a C18 column with a mixture of water–acetonitrile–acetic acid (1000:50:3) including 30 mg L−1 1-hydroxyethane-1,1-diphosphonic acid (HEDP), acetonitrile and methanol as the mobile phase, and calculated as 5-caffeoyl quinic acid (5-CQA). The Folin-Ciocalteu method was used for the measurement of total polyphenols, and calculated as 5-CQA. As the roasting increased, with both varieties, CGAs decreased, although most of the total polyphenols did not change. Therefore, a difference in roasting causes a change concerning the chemical structure of CGAs. However, the change substances had a hydroxyl group, which came from the structure of CGAs, and the possibility that had antioxidant ability was suggested.

Study of composition of espresso coffee prepared from various roast degrees of Coffea arabica L. coffee beans

Espresso coffee samples prepared at various roasting degrees defined according to its basic conventional classification (light, medium, medium-dark and dark roasted) were analyzed by ultra-performance liquid chromatography/tandem mass spectrometry. Obtained raw data were processed using multivariate statistical analysis (Principal Component Analysis, PCA) to evaluate chemical differences between each roasting degrees (untargeted part of study). All four roasting degrees were resolved in appropriate Score plot. Orthogonal Projections to Latent Structures provided signals of significant markers describing the differences among particular roasting degrees. Detailed interpretation of those signals by targeted LC/MS2 analysis revealed four groups of compounds. The first two groups involve chlorogenic acids and related lactones. The signals of other two sets of markers were ascribed to some specific atractylosides and particular melanoidins. Ratios of contents of selected representatives of each group to the sum of all identified markers were proposed as definite parameters for determination of roasting degree of Brazilian coffee Arabica.

배전조건이 아라비카 커피의 이화학적 성질에 미치는 영향

Effects of roasting on physical (weight, volume, density and color) and chemical properties (total phenol, caffeine, chlorogenic acid and antioxidant properties) of three Arabica coffee beans (Brazil Bourbon, Indonesia Mandheling and Kenya Tatu) were investigated. A steady weight loss, volume increase, and bean density decrease were observed during the roasting process. The L*, a*, and b* values tended to decrease as the roasting temperature and time increased. Caffeine level was approximately 0.73% in green beans, and increased to 40-67% for darker roasts. Green beans contained the highest chlorogenic acid content, which decreased as the roasting temperature and time increased. The light- and medium-roasted coffee showed the highest total phenolol contents. The antioxidant activities were measured using DPPH and ABTS. The light-roasted coffee beans showed the highest antioxidant activities, and an approximately 36-51% loss in antioxidant activity was observed after further roasting. The flavor patterns of roasted coffee beans were analyzed using an electronic nose system based on gas chromatography. This analysis demonstrated that an electronic nose system can be applied to identify the green bean variety and the degree of roasting.

Discrimination between Arabica and Robusta Coffees Using Hydrosoluble Compounds: Is the Efficiency of the Parameters Dependent on the Roast Degree?

Coffea arabica (arabica) and Coffea canephora (robusta) are the most important coffee species. Arabica has higher commercial value and, in general, more favorable sensory characteristics. After roasting, analytical methods are required to differentiate species. Blends with different proportions of arabica/robusta coffees, roasted at three degrees were studied. Color parameters and the levels of chlorogenic (5-CQA) and nicotinic acids, caffeine, and trigonelline were evaluated. Hydrosoluble compounds were analyzed by their efficiency to discriminate coffee species, considering different roast degrees. Caffeine was a good discriminator, regardless of roast degree. The roast degree influenced the efficiency of discrimination of the other hydrosoluble compounds. A model using color parameters and the variables Ratio (5-CQA/caffeine contents ratio) and Sum (sum of nicotinic acid and trigonelline contents) was proposed to the estimation of roasting degree. Considering the use of heat-labile compounds, the discrimination among coffee species should be carried out in two steps: first, the characterization of roasting degree, and subsequently the appropriate parameters are defined for each roasting degree. Thus, the combined use of color parameters and hydrosoluble compounds could be useful to help the differentiation of coffee species in blends of roasted samples.

Investigating the effect of roasting on functional properties of defatted hazelnut flour by response surface methodology (RSM)

The effect of roasting on functional properties of defatted hazelnut flours was evaluated by using response surface methodology (RSM). Color, water absorption capacity, emulsion and foaming properties were the main responses that determine the degree of roasting. After roasting of hazelnuts, the oil absorption and water absorption capacity, foam and emulsion stability of the flour were increased, whereas bulk density, foaming capacity and emulsion activity of flours decreased. The roasting temperature was found to be the main factor affecting color development, emulsion properties and foaming capacity. The maximum responses for color, emulsion and foaming properties were obtained at 140 °C and 40 min from the regression equations. RSM is a useful tool which can be applied to adjust the desired functional properties of flours. The results indicated that roasted defatted hazelnut flours may have a good potential to be used as value-added food ingredients, similar to other protein sources with various functional properties for food applications due to their nutritional value and improved functionality.

Understanding flavour perception of espresso coffee by the combination of a dynamic sensory method and in-vivo nosespace analysis

The first goal of this work was to gain insight into the mechanism underlying flavour perception and aroma release by coupling two real-time methods: Temporal Dominance of Sensations (TDS) and nosespace (NS) analysis via Proton Transfer Reaction–Time of Flight–Mass Spectrometry (PTR–ToF–MS). The second goal was to investigate the impact of roasting degree and sugar addition on aroma release and perception in espresso coffee.A set of four coffee samples, two roasting degrees and two sugar levels, has been used for both sensory and instrumental measurements. The in-mouth flavour evolution in terms of dominant sensations was measured by mean of TDS carried out by 18 trained judges with a 9-attribute list (Sweet, Sour, Bitter, Astringent, Roasted, Burnt, Caramel, Nutty and Vegetal). The same judges were subjected simultaneously to NS analysis in order to identify and quantify the volatile compounds reaching their olfactory receptors during coffee consumption.A significant effect of roasting was observed with both techniques. More compounds and in larger quantity were released when increasing roasting degree, which was described sensorially as a greater dominance of the attributes Burnt, Roasted, Astringent and Bitter. Sugar addition did not significantly affect the aroma release of volatile compounds as demonstrated by the NS profiles of judges while changing completely the way the coffee was sensorially perceived in mouth. As expected, sweet taste became dominant over bitter and sour but it increased more globally the flavour complexity with Caramel and Nutty notes reducing the Roasted or Burnt ones. This result emphasises the presence of taste–smell perceptual interactions, due to congruence effect between sweet taste and some flavours of coffee, and the potentialities of this combination of dynamic methods to study them. Besides, the treatment of NS data using clustering methods revealed two different release behaviours, which permitted to identify potential TDS markers.

Effect of Roasting Conditions on Concentration in Elements of Vietnam Robusta Coffee

Abstract Vietnam Robusta Coffee was roasted at different roasting degree and roasting temperature and 9 element concentrations (K, Mg, Ca, Na, Fe, Cu, Mn, Zn and Pb) of roasted coffee were analyzed by Flame atomic absorption method (FAAS) in this study. The results showed that the concentrations were ranged in 1447.97 ~ 1342.10 (mg/100g), 768.22 ~ 1259.44 (μg/g),10.35 ~ 13.15 (μg/g), and 17.38 ~ 20.97 (μg/g) for element of K, Ca, Cu and Mn in green and roasted coffee beans, respectively. All determined elements were the smallest value in green coffee, then increased with increasing roasting level and reached the highest value in Spain roast (roasting temperature of 250°C). Mg concentration ranged in 682.70 ~ 3647.73 (μg/g); Fe concentration ranged in 37.20 ~ 53.44 (μg/g); Zn concentration ranged in 5.97 ~ 6.89 (μg/g) and Pb concentration ranged in 2.18 ~ 15.04 (μg/100g). Concentrations of all determined elements didn’t change with the increased roasting process.

Influence of storage on volatile profiles in roasted almonds (Prunus dulcis).

Hexanal, peroxide value, and lipid hydroperoxides are common indicators of lipid oxidation in food products. However, these markers are not always reliable as levels are dynamic and often can be detected only after significant oxidation has occurred. Changes in the volatile composition of light- and dark-roast almonds were evaluated during storage over 24 weeks at 25 or 35 °C using headspace solid phase microextraction (HS-SPME) gas chromatography-mass spectrometry (GC-MS). Several volatile changes were identified in association with early oxidation events in roasted almonds. Hexenal decreased significantly during the first 6 weeks of storage and did not increase above initial levels until 20-24 weeks of storage depending upon the degree of roast. In contrast, levels of 1-heptanol and 1-octanol increased at 16-20 weeks, depending upon the degree of roast, and no initial losses were observed. Seventeen new compounds, absent in raw and freshly roasted almonds but detectable after 6 weeks of storage, were identified. Of these, 2-octanone, 2-nonanone, 3-octen-2-one, 2-decanone, (E)-2-decenal, 2,4-nonadienal, pentyl oxirane, and especially acetic acid increased significantly (that is, >10 ng/g). The degree of roasting did not correlate with the levels of these compounds. Significant decreases in roasting-related aroma volatiles such as 2-methylbutanal, 3-methylbutanal, furfural, 2-phenylacetaldehyde, 2,3-butanedione, 2-methylpyrazine, and 1-methylthio-2-propanol were observed by 4 weeks of storage independent of the degree of roast or storage conditions.

Caracterização física de café após torrefação e moagem

Flowability is an important characteristic of handling process for efficiency and reliability purpose of post-harvest operations, which are governed by the physical properties of the product. Physical properties determination is an important factor for formulation of machinery projects and sizing of post-harvest operations, which may impact considerably on the products quality, influencing directly the operation cost and company profit. Thus, the objective of this work was to evaluate and determinate some physical properties (repose angle, unit and bulk density, porosity and color coordinates, particle size, moisture content, water activity, angle of internal friction and effective angle of internal friction) of coffee, such as to evaluate the influence of different roast and grinding degrees over these properties. Crude grain coffee ( Coffea canephora and Coffea arabica ), dehulled and dried were used. These were roasted at two levels: medium light and medium-dark brown, which Agtron numbers are, respectively, SCAA#65 and SCAA#45. After roasting process, grains were grinded at three particle sizes (thin, medium and thick). Both particle size and roast degree significantly affected physical properties of coffee. Coffee samples roasted at medium dark level obtained lower values of moisture content, water activity, repose angle, bulk and real density. Coffee samples grinded at level thin presented an increase of angle of internal friction and effective angle of internal friction, repose angle, bulk and real density, porosity and decrease of water activity values.

Antioxidant effectiveness of ground roasted coffee in raw ground top round beef with added sodium chloride

Rosemary extracts are commonly utilized in the meat industry to control oxidation. Roasted coffee, a source of antioxidants, was investigated for its utility as a less costly rosemary replacement for meat. Ground beef with 0–2 g salt/100 g was treated with rosemary extract (0.1 mL/100 g, positive control), light roasted, medium roasted or dark roasted coffee (0.1 g/100 g) and stored for 7 days at 4 °C. Coffee was characterized by melanoidins, chlorogenic acid content, and metal chelation. Ground beef was evaluated for CIE L* (lightness), a* (redness), and b* (yellowness) values and lipid oxidation products. Increasing roast degree increased melanoidins and decreased chlorogenic acids. Salt treated samples developed higher thiobarbituric reactive substances values. Dark roasted coffee showed the greatest antioxidant capacity in salted beef after 7 days. Rosemary maintained the highest a* for all salt levels. Of all antioxidants, dark roast coffee showed the greatest % aldehyde inhibition for pentanal (86%), hexanal (90.3%), octanal (74.8%), and nonanal (60.3%) after 7 days in 2 g/100 g salted beef compared to control without added antioxidants. These results suggest that roasted coffee could act as an effective natural antioxidant in beef, extending its shelf-life, even in the presence of NaCl, which typically increases lipid oxidation levels.

Roasting process affects the profile of diterpenes in coffee

There is no consensus in the literature regarding the decrease of kahweol and cafestol contents during coffee roasting, but it has been reported that these compounds can undergo dehydration under heat. Kahweol and cafestol were quantified in Arabica and Robusta coffees with different roasting degrees (2, 4, 6, 8 and 10 min at 230 °C). The structures of the diterpenes and the presence of derivative compounds were determined by liquid chromatography with UV–Vis and mass spectrometry detection. In the dark roast samples, dehydro derivatives were found. The roasting process influenced the level of diterpenes in both species of coffee, but the effect was dependent on the intensity of the process. Cafestol and kahweol were degraded (general losses from 60 to 75 % on a lipid basis) to dehydrocafestol and dehydrokahweol, respectively, after 8 min of process, which corresponds to the commercial roasting degree. On the other hand, the amounts of cafestol and kahweol (mg/100 g of coffee) remained stable during the roasting process due to relative increase in lipid concentration.

Evidence of different flavour formation dynamics by roasting coffee from different origins: On-line analysis with PTR-ToF-MS

Coffees from different origins were roasted to different roast degrees and along varying time temperature roasting profiles. The formation of volatile organic compounds (VOCs) during roasting was analyzed on-line by proton-transfer-reaction time-of-flight mass-spectrometry (PTR-ToF-MS). Coffee samples were Coffea arabica from Colombia, Guatemala (Antigua La Ceiba), Ethiopia (Yirga Cheffe, Djimmah) and Coffea canephora var. robusta from Indonesia (Malangsari). The roasting profiles ranged from high temperature short time (HTST) to low temperature long time (LTLT) roasting, and from medium to dark roast degree. The release dynamics of the on-line monitored VOCs differed for the different coffees and showed a strong modulation with the time–temperature roasting profile. While for Guatemalan coffee the formation of VOCs started relatively early in the roasting process, the VOC formation started much later in the case of Yirga Cheffe and Malangsari. Off-line analysis of the coffee brew augmented the measurements. These included headspace solid phase micro extraction gas chromatography mass spectrometry (HS SPME GC/MS), content of total solids, chlorogenic acids, caffeine, total polyphenols (Folin Ciocalteu), organic acids (ion chromatography), titratable acidity and pH. Some general trends, irrespective of the coffee origin, were observed, such as an increase in pH when going from an HTST to an LTLT profile or from a medium to dark roast degree. Furthermore, a decrease of total headspace intensity was observed from an HTST to an LTLT roasting profile. In general, the changes of the time temperature roasting profiles and/or the roast degree influenced the intensity of the respective coffee constituents as well as their relative composition differently for different coffee origins.

Effect of roasting conditions on carbon dioxide degassing behavior in coffee

CO2 is one of the major gases formed during coffee roasting, which has important implications on coffee's quality and packaging requirements. In this study, the residual CO2 content and CO2 degassing behavior of an Arabica coffee processed using a fluidized bed roaster, as affected by the roasting temperature–time conditions, were investigated. The results showed that positive correlations existed between the degree of roast (expressed as lightness value) and residual CO2, implying that lightness could be used as an indicator of initial CO2 content in roasted coffee. At the same degree of roast, coffee roasted with high-temperature–short-time process had significantly higher CO2 degassing rate than those with low-temperature–long-time process. Moreover, the CO2 releasing rate increased with the degree of roast. The degassing rate of CO2 in ground coffee was highly dependent on the grind size and roasting temperature, but less dependent on the degree of roast. The different degassing behaviors observed between roasted coffee samples were explained on the basis of chemical composition and microstructural differences.

Nosespace analysis by PTR-ToF-MS for the characterization of food and tasters: The case study of coffee

In the present work Proton Transfer Reaction-Mass Spectrometry was employed in the discrimination of coffee brews by means of nosespace analysis. Three different roasted and ground coffee samples originating from a single pure Arabica blend (medium roast, dark roast and decaffeinated medium roast) were prepared using a stove-top coffee maker. Coffees were submitted to five panelists over three replicates (45 sessions overall). In agreement with the results of brewed coffee headspace analysis, the nosespace data showed that greater differences could be encountered when different roast degrees were compared, rather than decaffeinated and non-decaffeinated. The comparison between headspace and nosespace analysis also showed that different coffees could be discriminated using different subsets of mass peaks, depending upon the mode of analysis. The results also disclosed the existence of reproducible and relevant differences between panelists, also in terms of discrimination ability.

On‐line process monitoring of coffee roasting by resonant laser ionisation time‐of‐flight mass spectrometry: bridging the gap from industrial batch roasting to flavour formation inside an individual coffee bean

Resonance-enhanced multiphoton ionisation time-of-flight mass spectrometry (REMPI-TOFMS) enables the fast and sensitive on-line monitoring of volatile organic compounds (VOC) formed during coffee roasting. On the one hand, REMPI-TOFMS was applied to monitor roasting gases of an industrial roaster (1500 kg/h capacity), with the aim of determining the roast degree in real-time from the transient chemical signature of VOCs. On the other hand, a previously developed μ-probe sampling device was used to analyse roasting gases from individual coffee beans. The aim was to explore fundamental processes at the individual bean level and link these to phenomena at the batch level. The pioneering single-bean experiments were conducted in two configurations: (1) VOCs formed inside a bean were sampled in situ, i.e. via a drilled μ-hole, from the interior, using a μ-probe (inside). (2) VOCs were sampled on-line in close vicinity of a single coffee bean's surface (outside). The focus was on VOCs originating from hydrolysis and pyrolytic degradation of chlorogenic acids, like feruloyl quinic acid and caffeoyl quinic acid. The single bean experiments revealed interesting phenomena. First, differences in time-intensity profiles between inside versus outside (time shift of maximum) were observed and tentatively linked to the permeability of the bean's cell walls material. Second, sharp bursts of some VOCs were observed, while others did exhibit smooth release curves. It is believed that these reflect a direct observation of bean popping during roasting. Finally, discrimination between Coffea arabica and Coffea canephora was demonstrated based on high-mass volatile markers, exclusively present in spectra of Coffea arabica.

On-line solid–phase extraction using a C18 minicolumn coupled to a flow injection system for determination of caffeine in green and roasted coffee beans

A novel and fast method based on the solid phase extraction (SPE) coupled to a flow injection system for the determination of caffeine in coffee beans was developed. The caffeine extraction of coffee beans was carried out with hot water. A C18 reverse-phase mini-column was coupled to a continuous flow manifold to carry out the on-line SPE and the quantification of caffeine from aqueous extracts. Column length, retention time, elution volume, extracting solution and injection volume were evaluated. The retention time was of 90s and the elution was carried out with 400μL of a methanol:water mixture (25:75). The proposed on-line SPE was compared against a chloroform extraction from aqueous extracts. With the proposed method the sample preparation was minimised and the sample throughput was increased (10determination/h) because no dilution was required. Green coffee beans and beans with different roasting degree were analyzed.

Headspace–Solid Phase Microextraction–Gas Chromatography–Tandem Mass Spectrometry (HS-SPME-GC-MS2) Method for the Determination of Pyrazines in Perilla Seed Oils: Impact of Roasting on the Pyrazines in Perilla Seed Oils

A new headspace (HS)-solid phase microextraction (SPME)-gas chromatography-tandem quadrupole mass spectrometry (GC-MS(2)) was established for the simultaneous characterization and quantitation of pyrazines in perilla seed oils. HS-SPME conditions such as fiber choice, extraction temperature, and adsorption times were tested. The established GC-MS(2) showed low detection limit (LOD) and high specificity, recovery, and precision for analysis of pyrazines in perilla seed oils. The LODs for the pyrazines were in the range of 0.07-22.22 ng/g oil. The relative standard deviations (RSDs) for the intra- and interday repeated analyses of pyrazines were less than 9.49 and 9.76%, respectively. The mean recoveries for spiked pyrazines in perilla seed oil were in the range of 94.6-107.92%. Perilla seed oils were obtained by mechanical pressing from perilla seeds roasted to different degrees of roasting (mild, medium, medium dark, and dark roasting). Fourteen pyrazine compounds in perilla seed oils were isolated, identified, and quantitated. Among them, 2-methyl-3-propylpyrazine, tetramethylpyrazine, and 2,3-diethyl-5-methylpyrazine were the first identified in perilla seed oils. Degree of roasting influenced greatly the composition and contents of pyrazines in perilla seed oils. In light-roasted perilla seed oil, 2,5-dimethylpyrazine was the most predominant pyrazine. However, in dark-roasted perilla seed oil, 2-methylpyrazine was the most abundant pyrazine in the oil, representing 38.3% of its total pyrazine content. Dark-roasted perilla seed oil contains 16.78 times higher quantity of pyrazines than light-roasted perilla seed oil. This represents the first report on the quantity of pyrazines in perilla seed oils.

Exploratory and discriminative studies of commercial processed Brazilian coffees with different degrees of roasting and decaffeinated

The fingerprints of the volatile compounds of 21 commercial Brazilian coffee samples submitted to different industrial processing i.e. decaffeinated or different roasting degrees (traditional and dark) were studied. The volatiles were collected by headspace solid phase microextraction (HS-SPME) and analyzed by GC-FID and GC-MS. The chromatographic data matrices (fingerprints) obtained were explored by the principal component analysis (PCA) and partial least squares - discriminative analysis (PLS-DA). Initially the chromatographic profiles were aligned by the algorithm correlation optimized warping (COW). The PCA showed the discrimination of the decaffeinated coffees from the others with both the SPME fibres used. This separation probably occurred due to the loss of some volatile precursors during the decaffeination process, such as sucrose. For both the fibres tested, PDMS/DVB and CX / PDMS SPME, the PLS-DA models correctly classified 100% of the samples according to their roasting degree: (medium and dark), the main differences being the concentrations of some of the volatile compounds such as 2-methyl furan, 2-methylbutanal, 2,3-pentanedione, pyrazine, 2-carboxyaldehyde pyrrole, furfural and 2-furanmethanol.

Effect of vacuum roasting on acrylamide formation and reduction in coffee beans

Coffea arabica beans were roasted in an oven at 200°C for increasing lengths of time under vacuum (i.e. 0.15kPa). The samples were then analysed for colour, weight loss, acrylamide concentration and sensory properties. Data were compared with those obtained from coffee roasted at atmospheric pressure (i.e. conventional roasting), as well as at atmospheric pressure for 10min followed by vacuum treatment (0.15kPa; i.e. conventional-vacuum roasting). To compare the different treatments, weight loss, colour and acrylamide changes were expressed as a function of the thermal effect received by the coffee beans during the different roasting processes. Vacuum-processed coffee with medium roast degree had approximately 50% less acrylamide than its conventionally roasted counterpart. It was inferred that the low pressure generated inside the oven during the vacuum process exerted a stripping effect preventing acrylamide from being accumulated. Vacuum-processed coffee showed similar colour and sensory properties to conventionally roasted coffee.

A Kinetics and Modeling Study of Coffee Roasting Under Isothermal Conditions

In this study, changes in lightness, roast loss, residual CO2, and total volatiles of an Arabica coffee were investigated under isothermal conditions at 220, 230, 240, and 250 °C. The lightness of the roasted coffee, expressed as L* value, followed two-stage processes that could be modeled using pseudo first-order reaction models, giving activation energies of 59.7 and 170.2 kJ/mol for the first and second stages, respectively. Roast loss data also exhibited two-stage behavior, but followed zero-order reaction kinetics, with activation energies of 52.9 and 181.3 kJ/mol for the first and second stage, respectively. The first-to-second stage transition for L* value and roast loss occurred at light-medium roast. Residual CO2 in the coffee beans correlated negatively with L* value below medium-dark roast degree. However, a reversed correlation was observed above dark roast degree. The volatile compounds generated in roasted coffee were highly dependent on roasting temperature and roast degree.