Published in Food Research International 48, 57

TITLE: Extraction of coffee antioxidants: impact of brewing time and method
ARTICLE TYPE: Research article
AUTHORS: Iziar A. Ludwiga, Lidia Sancheza, Bettina Caemmererb, Lothar W.
Krohb, M. Paz De Peñaa*, Concepción Cida
a
Department of Nutrition, Food Science, Physiology, and Toxicology, School of
Pharmacy, University of Navarra, E-31080-Pamplona, Spain
b
Institut für Lebensmittelchemie, Technische Universität Berlin, Gustav-Meyer-Allee
25, D-13355 Berlin, Germany
Published in Food Research International 48, 57-64 (2012)
*Corresponding author:
M. Paz De Peña
Department of Nutrition, Food Science, Physiology, and Toxicology
School of Pharmacy, University of Navarra
C/ Irunlarrea 1
E-31080-Pamplona, Spain
Tel: +34 948 425600 (806580)
Fax: +34 948 425740
E-mail address: mpdepena@unav.es
ABSTRACT
The aim of this work was to study the extraction behavior of the main coffee
antioxidants (caffeoylquinic acids, melanoidins and caffeine) and the antioxidant
capacity, during brewing time in the most widely consumed coffee brew methods (filter
and espresso) in coffee. Antioxidant capacity by colorimetric assays (Folin-Ciocalteau,
ABTS and DPPH) and electron spin resonance spectroscopy techniques (Fremy’s salt
and TEMPO) were analyzed. In espresso coffee, more than 70% of the antioxidants
(except dicaffeoylquinic acids, diCQA) of a coffee brew were extracted during the first
8 s. In filter coffee, a U-shape antioxidants extraction profile was observed, starting later
(after 75s) in Vietnam coffee than in Guatemala one, probably due to different
wettability. Other technological parameters, such as turbulences and a longer contact
time between water and ground coffee in filter coffeemaker, increased extraction
efficiency, mainly in less polar antioxidant compounds as diCQA. In conclusion, these
technological factors should be considered to optimize coffee antioxidants extraction
that can be used as ingredients for functional foods.
KEYWORDS: Antioxidants, brewing time, coffee, Maillard reaction products,
phenolics.
1. INTRODUCTION
Several chronic diseases, such as cancer, cardiovascular, inflammatory, and
neurogenerative pathologies are associated with oxidative stress (Aruoma, 1999; Beal,
1995; Dorea & da Costa, 2005). Beside fruits and vegetables, plant beverages such as
coffee brew have been proposed as an important source of antioxidants in human diet
(Pulido, Hernandez Garcia, & Saura Calixto, 2003; Svilaas, Sakhi, Andersen, Svilaas,
Strom, & Jacobs, 2004). The antioxidant capacity of coffee brew is attributed to both
antioxidants originally present in coffee beans, like phenolic compounds, and roastinginduced antioxidants, like melanoidins and other Maillard Reaction Products (MRP)
(Borrelli, Visconti, Mennella, Anese, & Fogliano, 2002; Crozier, Jaganath, & Clifford,
2009; del Castillo, Ames, & Gordon, 2002).
The most abundant phenolic compounds of coffee are chlorogenic acids (CGA). CGA
are known for their contribution to the final acidity, astringency, and bitterness of the
coffee brew, but also for their potent antioxidant properties (Moreira, Monteiro,
Ribeiro-Alves, Donangelo, & Trugo, 2005; Natella, Nardini, Giannetti, Dattilo, &
Scaccini, 2002; Trugo & Macrae, 1984; Variyar, Ahmad, Bhat, Niyas, & Sharma,
2003). During roasting, CGA are partially degraded and at least partly incorporated in
coffee melanoidins through non-covalent or covalent bounds (Bekedam, Schols, van
Boekel, & Smit, 2008; Nunes & Coimbra, 2010). Melanoidins are generally defined as
the browned-colored, high-molecular-weight, nitrogenous end products of the Maillard
reaction. They are formed during roasting process of coffee. Beside its contribution to
flavor and color, one of the important functional properties of melanoidins is its
antioxidant activity (Caemmerer & Kroh, 2006; C. Delgado-Andrade & Morales, 2005;
López-Galilea, Andueza, Leonardo, de Peña, & Cid, 2006; Rufián-Henares & Morales,
2007). Although there is still a discussion about their bioavailability, it is clear that at
least they may act as prebiotic or even antimicrobial depending on their nature and
concentration (Borrelli & Fogliano, 2005; Rufián-Henares & de la Cueva, 2009). Also
caffeine or its metabolites in humans have been proposed as antioxidant compounds
against lipid peroxidation induced by reactive oxygen species (Devasagayam, Kamat,
Mohan, & Kesavan, 1996; Lee, 2000). However, although caffeine has been extensively
studied from the pharmacological point of view, less attention has been paid to its
potential antioxidant activity that may be overshadowed by phenolic compounds and
MRP.
Brewing process is essential for the antioxidant composition and health properties of a
coffee brew, because the contact of water with roasted coffee grounds is the crucial step
for extraction of coffee compounds. Other factors, such as origin or variety of coffee
beans, blending, roasting degree and grinding also play a key role in coffee
composition. Among the several brewing techniques, filter coffee (drip filter) is the
most widely used coffee brew obtained by infusion method, whereas espresso coffee is
the most appreciated coffee brew produced by pressure method. In drip filtration
methods, water at 92-96 ºC flows through a hardly compressed ground coffee bed and
the extract drips from the brewing chamber into the pot. Turbulence in the brewing
chamber prevents water from becoming saturated (Lingle, 1996). In pressure methods,
water at approximately 9 bars and 88-92ºC is forced to go through coffee grounds
compacted in a small brewing chamber (coffee cake). Also rapid brewing time and fine
particle size are necessary (Lingle, 1996). Many chemical species identified in roasted
coffee, including antioxidants, exhibit different extraction rates that may also be
influenced by the choice of brewing technique and conditions (Peters, 1991; Petracco,
2001; Petracco, 2005).
Even though the brewing time is given by the coffee brewing technique, the knowledge
of extraction behavior of the main coffee antioxidants during this time might induce to
know the technological factors with major impact on antioxidants extraction. Thus, it
could be possible to obtain not only coffee brews with higher antioxidant capacity, but
also coffee extracts with health properties that can be used as ingredients in functional
foods. For these reasons, the aim of this work was to study the extraction behavior of
the main coffee antioxidants and the antioxidant capacity, during brewing time in the
most widely consumed coffee brew procedures (filter and espresso).
2. MATERIALS AND METHODS
2.1. Chemicals and reagents. The methanol (spectrophotometric and HPLC grade) and
Folin-Ciocalteau reagent were from Panreac (Barcelona, Spain). ABTS (2,2’-Azinobi(3-ethylbenzo-thiazonile-6-sulfonic acid) diammonium salt), potassium persulfate,
DPPH-
(2,2-Diphenyl-1-picrylhydrazyl),
Trolox
(6-hydroxy-2,5,7,8-tetramethyl-
chroman-2-carboxylic acid), dipotassium hydrogen phosphate, potassium dihydrogen
phosphate, sodium chloride, Fremy’s salt (potassium nitrosodisulfonate) and TEMPO
(2,2,6,6-tetramethyl-1-piperidin-1-oxyl)
were
purchased
from
Sigma-Aldrich
(Steinheim, Germany). Gallic acid was from Fluka (Madrid, Spain). Pure reference
standards of 5-caffeoylquinic acid (5-CQA) and caffeine were obtained from SigmaAldrich (Steinheim, Germany) and pure reference standards of 3,4-, 3,5- and 4,5dicaffeoylquinic acids were purchased from Phytolab (Vestenbergsgreuth, Germany). A
mixture of 3-CQA, 4-CQA, and 5-CQA was prepared from 5-CQA using the
isomerization method of Trugo and Macrae (1984), also described in Farah et al. (2005).
2.2. Coffee brew samples. Roasted coffee from Guatemala (Coffea arabica, 3.03 %
water content, L* = 25.40 ± 0.69, roasted at 219 ºC for 905 s) and Vietnam (Coffea
canephora var. robusta, 1.59 % water content, L* = 24.92 ± 0.01, roasted at 228 ºC for
859 s) was provided by a local factory. The L* value was analyzed by means of a
tristimulus colorimeter (Chromameter-2 CR-200, Minolta, Osaka, Japan) using the D65
illuminant and CIE 1931 standard observer. The instrument was standardized against a
white tile before sample measurements. Ground roasted coffee was spread out in an
l cm Petri plate, and the L* value was measured in triplicate on the CIELab scale.
Roasted coffee beans were ground to a powder in a Moulinex coffee grinder (model
Super Junior “s”, Paris, France) for 20 s immediately before sample preparation. Filter
Coffee Brew was prepared from 36 g of ground roasted coffee for a volume of 600 mL,
using a filter coffee machine (model Avantis 70 Aroma plus, Ufesa, Spain). Extraction
took approx. 6 min at 90 ºC. Five fractions for filter coffee were collected sequentially
every 75 s. Espresso Coffee Brew was prepared from 7 g of ground roasted coffee for a
volume of 45 mL using an espresso coffee machine (model Saeco Aroma, Italy). Three
fractions for espresso coffee were collected sequentially every 8 s. Coffee brews and
fractions were lyophilized using a CRYODOS Telstar (Terrassa, Spain) and stored at 18ºC until sample analysis.
2.3. pH. The pH measurements of coffee brews and fractions were performed with a
Crison Basic 20pH-meter.
2.4. Browned compounds (Abs 420 nm). Fifty microliters of coffee brew or fraction
were diluted up to 2 mL with deionized water. Browned compounds were quantified by
measuring the absorbance of the sample at 420 nm after exactly 1 min, in a 3 mL
capacity cuvette (1 cm length) with a Lambda 25 UV-VIS spectrophotometer (PerkinElmer Instruments, Madrid, Spain) connected to a thermostatically controlled chamber
(25 ºC) and equipped with UV Win-Lab software (Perkin Elmer).
2.5. Folin-Ciocalteau (FC) assay. The Folin-Ciocalteau reducing capacity of coffee or
fractions was performed according to the Singleton´s method (Singleton & Rossi,
1965). For every coffee sample, 1:10 dilutions with demineralized water were prepared,
and 500 μL of Folin-Ciocalteau reagent were added to 100 μL of the coffee sample
solution. After 2 min delay, 1.5 mL of a 7.5% sodium carbonate solution was added.
Next, the sample was incubated in darkness at room temperature for 90 min. The
absorbance of the sample was measured at 765 nm in a Lambda 25 UV-VIS
spectrophotometer (Perkin Elmer Instruments, Madrid, Spain). Gallic acid (GA) was
used as reference, and the results were expressed as milligrams of GA per mililiter of
coffee brew or fraction.
2.6. Antioxidant capacity by ABTS assay. The antioxidant capacity measured with
ABTS was carried out according to the method described by Re et al. (1999) with some
modifications. The radicals ABTS·+ were generated by the addition of 2.45 mM
potassium persulfate to an 7 mM ABTS solution prepared in phosphate-buffered saline
(PBS, pH 7.4) and allowing the mixture to stand in darkness at room temperature for at
least 12 h before use. The ABTS·+ stock solution was adjusted with PBS to an
absorbance of 0.7 (±0.02) at 734 nm in a 1 cm cuvette at 25 ºC (Lambda 25 UV, VIS
spectrophotometer, Perkin Elmer Instruments, Madrid, Spain). An aliquot of 50 µL of
coffee sample diluted with demineralized water (5:1000 to 15:1000) was added to 2 mL
of ABTS·+ reagent and the absorbance was monitored for 18 min at 25 ºC. Calibration
was performed with Trolox solution (a water-soluble vitamin E analogue) and total
antioxidant capacity was expressed as micromoles (μmol) of Trolox per mililiter of
coffee brew or fraction.
2.7. Antioxidant capacity by DPPH assay. The antioxidant capacity was measured
using the DPPH decolorization assay (Brand-Williams, Cuvelier, & Berset, 1995). A
6.1x10–5 M DPPH· methanol solution was prepared immediately before use. The DPPH·
solution was adjusted with methanol to an absorbance of 0.7 (±0.02) at 515 nm in a
1 cm cuvette at 25 ºC (Lambda 25 UV, VIS spectrophotometer, Perkin Elmer
Instruments, Madrid, Spain). Fifty microliters of appropriate diluted coffee sample
(1:100 to 3:100) was added to DPPH· solution (1.95 mL). After mixing, the absorbance
was monitored at 515 nm for 18 min at 25 ºC. Calibration was performed with Trolox
solution and the total antioxidant capacity was expressed as micromoles (μmol) of
Trolox per mililiter of coffee brew or fraction.
2.8. Antioxidant capacity by Electro Spin Resonance (ESR) spectroscopy. The ESR
spectroscopy measurements were performed with Fremy´s salt and TEMPO as
stabilized radicals with the same procedure described by Roesch et al. (2003) and
modified by Caemmerer & Kroh (2006). For the investigation with Fremy’s salt,
100 μL of every coffee sample diluted 250-fold with demineralized water was allowed
to react with an equal volume of an aqueous 1 mM Fremy’s salt solution prepared in
50 mM phosphate buffer (pH 7.4). ESR spectra were recorded every 40 s for 30 min.
For the investigation with TEMPO, aliquots of 300 μL of coffee sample were allowed to
react with 100 μL of 1 mM TEMPO solution. ESR spectra were obtained after 120 min,
by which time the reaction was complete. Microwave power was set at 10 dB.
Modulation amplitude, center field, and sweep width were set at 1.5, 3397, and 71 G,
respectively. Both Fremy’s salt and TEMPO antioxidant activity were calculated as
Trolox equivalents and expressed as micromoles (μmol) of Trolox per mililiter of coffee
brew or fraction.
2.9. Chlorogenic acids (CGA) and caffeine. Extract preparation and cleanup were
carried out according to Bicchi et al. (1995). The compounds were analyzed by HPLC
following the method described by Farah et al. (2005), with some modifications. HPLC
analysis was achieved with an analytical HPLC unit model 1100 (Agilent Technologies,
Palo Alto, CA, USA) equipped with a binary pump and an automated sample injector. A
reversed-phase Hypersil-ODS (5 µm particle size, 250 x 4.6 mm) column was used at
25 ºC. The sample injection volume was 100 µL. The chromatographic separation was
performed using a gradient of methanol (solvent A) and Milli-Q water acidulated with
phosphoric acid (pH 3.0, solvent B) at a constant flow of 0.8 mL/min starting with 20%
solvent A. Then solvent A was increased to 50% within 15 min to be maintained at 50%
for 9 min and, finally, to return to initial conditions (20% solvent A) in 3 min. Detection
was accomplished with a diode-array detector, and chromatograms were recorded at
325 nm for CGA and 276 nm for Caffeine. Identification of CGA and caffeine was
performed by comparing the retention time and the photodiode array spectra with those
of their reference compounds. Quantification of 5-caffeoilquinic (5-CQA) and caffeine
was made by comparing the peak areas with those of the standards. Quantification of
the other chlorogenic acids (CGA) was performed using the area of 5-CQA standard
combined with molar extinction coefficients of the respective CGA as reported by
Trugo and Macrae (1984) and Farah et al. (2005).
2.10. Statistical analysis. Each parameter was analyzed in triplicate. Results are shown
as means ± standard deviations. Student’s t-test was applied for each antioxidant
capacity assay to know whether there were differences between both coffees in each
coffee brew. One-way analysis of variance (ANOVA) was applied for each parameter to
compare antioxidants extraction among fractions in each coffee brew sample. A TTukey test was applied as a test a posteriori with a level of significance of 95%. All
statistical analyses were performed using the SPSS v.15.0 software package.
3. RESULTS AND DISCUSSION
3.1. Coffee fractions Volumes
The volumes of the coffee brews and fractions obtained by espresso and filter
coffeemakers are shown in Table 1. The volumes of the three espresso coffee fractions
were quite similar, ranging from 14 to 17 mL. In contrast, the volumes of the filter
coffee fractions increased from F1 (76-80 mL) up to F3 (160-186 mL) and then
decreased to F5 (26-54 mL), showing an inverted U-shape profile.
To extract coffee compounds during the brewing process, the dry coffee grounds must
first absorb water. Once the water has completely surrounded a coffee particle, both
inside and out, the coffee extractable material begins to move out of the bean’s cellular
structure and into the surrounding water. Because espresso coffeemaker applies constant
pressure that forces water through the coffee grounds with a constant flow, the coffee
fraction volumes were similar among each other. However, in filter coffee no
mechanical forces are applied, and the brew volume dripping out from the extraction
chamber depends on the water amount, and consequently on the water pressure in the
extraction chamber of the coffeemaker according to Darcy’s law (Petracco, 2005).
Furthermore, at the beginning of the filter extraction process, part of the water is
absorbed by coffee grounds. In an espresso coffeemaker, water is forced to go through
the coffee cake, but, in a filter coffeemaker, during wettability, 1 g of coffee will absorb
2 mL of water as a general rule (Lingle, 1996). This fact explains the low volume
obtained for F1 (0-75 s). With time, water fills the extraction chamber increasing the
pressure and favoring that water passes through the coffee bed, which leads to higher
volumes in the middle fractions. At the end of the brewing procedure, pressure
decreases when the water reservoir depletes, giving the lowest volume in the last
fraction (F5).
3.2. Antioxidant capacity of coffee fractions
The antioxidant capacity of the coffee brews and fractions obtained by espresso and
filter coffeemakers was measured by means of three colorimetric assays (FolinCiocalteau, ABTS and DPPH) and two electron spin resonance (ESR) spectroscopy
techniques (Fremy´s salt and TEMPO) and the results are shown in Figure 1 to 5.
The Folin-Ciocalteau assay is based on an electron-transfer reaction. Although this is
the most popular method to evaluate the total phenolic compounds, the Folin-Ciocalteau
reagent can be reduced by many electron-donors, not only phenolic compounds (Huang,
Ou, & Prior, 2005). Two different stable radicals (ABTS·+ and DPPH·) were chosen to
assess the radical scavenging activity in coffee fractions. These radicals react
energetically with hydrogen-donors, such as phenolic compounds, being DPPH· likely
more selective in the reaction with H-donors than ABTS·+ (Huang et al., 2005). In these
three colorimetric assays, Vietnam coffee brews showed significantly (p<0.01) higher
antioxidant capacity than Guatemala ones. The results were similar to those reported by
other authors in espresso and filter coffee brews (Pérez-Martinez, Caemmerer, De Peña,
Cid, & Kroh, 2010; Sánchez González, Jiménez Escrig, & Saura Calixto, 2005).
Espresso coffee fractions from both coffees showed a remarkable decrease in
antioxidant capacity with brewing time. More than 70% of the overall antioxidant
capacity of an espresso coffee brew was found in F1 (0-8 s), whereas F3 accounted for
less than 12 %. These results demonstrate that the compounds responsible for the
antioxidant activity of an espresso coffee brew are mainly extracted at the beginning of
the brewing process and, afterwards, are diluted. Similar results were found by Alves et
al (2010) for DPPH antioxidant activity in espresso coffees with different brew lengths
(“short” to “long”). These authors also observed that the antiradical or reducing activity
of espresso coffee brew is not only dependent on total phenolic amounts measured by
Folin-Ciocalteau assay. This may be due to the fact that the Folin-Ciocalteau assay not
only evaluates phenolic compounds, but also because it is well known that roastinginduced antioxidants like Maillard reaction products (MRP), contribute to the overall
antioxidant capacity of coffee (Delgado-Andrade, Rufián-Henares, & Morales, 2005;
Pérez-Martinez et al., 2010).
To go deeper into the influence of brewing time on antioxidant capacity due to
phenolics or MRP, Electron spin resonance (ESR) spectroscopy was applied using
Fremy’s salt and TEMPO radicals. Mainly phenolic compounds can be detected when
Fremy’s salt is used as the stabilized radical, whereas TEMPO is mainly scavenged by
Maillard reaction products (MRP), such as melanoidins (Caemmerer & Kroh, 2006).
The results obtained with ESR spectroscopy (Figure 4 and 5) showed that Fremy´s salt
scavenging capacity was almost four times higher than TEMPO. Similar results were
reported by other authors who proposed that the phenolic antioxidants evaluated by
Fremy´s salt dominate the overall antioxidant capacity of coffee brews, whereas the
contribution of roasting-induced antioxidants is rather limited (Bekedam, Schols,
Cämmerer, Kroh, van Boekel, & Smit, 2008; Pérez-Martinez et al., 2010).
The ESR antioxidant capacity of espresso coffee fractions showed that F1 (0-8 s)
accounted for 75-81 % and for 86-89 % of the Fremy´s salt and TEMPO scavenging
capacity of an espresso coffee brew, respectively. Although antioxidant capacity due to
phenolics and measured by Fremy’s salt assay was the highest in the first fraction, 2025 % of the scavenging capacity was still found in F2 and F3. This could be due to a
slower extraction of those phenolics retained in the inner coffee particles and those
bound to melanoidins that need more time and water pressure to be released. The
highest percentages observed for TEMPO scavenging capacity in F1 indicate that MRP
antioxidants were mainly extracted during the first 8 seconds, whereas the last fraction
(16-24 s) only accounted for 1-2 %. These results agree with the significantly highest
values of Browned compounds (Abs 420 nm) showed in the first fraction (Table 2) that
clearly decreased in the next ones (F2 and F3).
Filter coffee fractions showed different antioxidant capacity extraction behaviors, being
also different in the two coffee samples in comparison to espresso coffee. In Guatemala
filter coffee, all antioxidant capacity assays showed a U-shape profile with the highest
concentration in F1 (0-75 s) and F5 (300-375 s) and the lowest in F3 (150-225 s).
However, in Vietnam coffee the U-shape antioxidant capacity extraction started after
75 s, showing F1 the lowest values. This could be due to a higher water absorption in
Vietnam coffee that leads to a longer wetting stage. The wettability depends on the
particle shape and size that may be different depending on factors like grinding that is
also influenced by coffee origin or variety and roasting degree (Lingle, 1996). In this
work, taking into account that roasting degree and grinding conditions were controlled
to be the same, different wettability may be due to the different brittleness of the coffee
beans. The increase of antioxidant capacity in the last fractions (F4 and F5) of filter
coffee brews could be due to the water pressure decrease that induces a lower flow and
a longer contact time between water and ground coffee. In fact, because the last fraction
(F5) had the lowest volumes (26 mL and 54 mL for Guatemala and Vietnam coffees,
respectively), their contribution to the antioxidant capacity of the overall coffee brew
was rather limited (~9 % and ~14 %, respectively).
The results of the antioxidant capacity due to phenolics and MRP, measured by ESR
spectroscopy in filter coffee fractions using Fremy’s salt and TEMPO as stabilized
radicals (Figures 4 and 5), also corroborate that the antioxidants extraction seems to be
delayed in Vietnam filter coffee. This was more pronounced in TEMPO antioxidant
capacity that mainly evaluates the scavenging activity of melanoidins which are
polymeric compounds with more difficult to be released without water pressure. In fact,
the Absorbance at 420 nm of Vietnam filter F1 fraction was significantly the lowest as
shown in Table 3. Moreover, taking into account the brew volume, only ~3 % of
TEMPO antioxidant capacity of the overall Vietnam filter coffee brew was extracted
during the first 75 seconds (F1), whereas ~37 % was found in F2 (75-150 s). So that, the
contribution of the first two fractions of Vietnam filter coffee to the overall TEMPO
antioxidant capacity was similar to the ~40 % found in Guatemala filter coffee F1.
3.3. Antioxidant compounds extraction
The antioxidant capacity of coffee brew is attributed to both, natural antioxidants, like
phenolic compounds, and roasting-induced antioxidants, like melanoidins and other
MRPs. To know the influence of brewing time on the main antioxidant compounds,
browned compounds (Abs 420 nm), caffeine and caffeoylquinic acids in coffee brews
fractions were quantified and the results are shown in Table 2 and 3. Browned
compounds, as previously discussed, were mainly extracted in those coffee fractions
with high TEMPO antioxidant capacity showing a high correlation (r=0.969, p<0.001).
Also caffeine has been proposed as an antioxidant compound against lipid peroxidation
induced by reactive oxygen species (Lee, 2000). Caffeine was in significantly higher
concentration in Vietnam espresso and filter coffee brews and fractions. It is very well
known that Robusta coffees are richer in caffeine than Arabica ones (Belitz, Grosch, &
Schieberle, 2009). Thus, caffeine might partially explain the higher antioxidant capacity
of Vietnam coffee brews that could not be attributed to the main chlorogenic acids that
were found in lower amounts in these coffee brews, as will be discussed later.
Traditionally, the higher antioxidant capacity of Robusta coffee brews has been
attributed to higher total phenolic compounds (usually measured by Folin Ciocalteau
technique), and then to chlorogenic acids because 5-CQA is the most abundant phenolic
in coffee. However, other authors (López-Galilea, de Peña, & Cid, 2007; Vignoli,
Bassoli, & Benassi, 2011) also observed higher antioxidant capacity but lower 5-CQA
amounts in brews prepared with Robusta coffee or torrefacto blends. These authors
reported high correlations between antioxidant capacity of coffee brews and caffeine,
suggesting that caffeine might be a good contributor to the antioxidant capacity or
reducing power of coffee brews. In the present work, also high correlations have been
found between antioxidant capacity assays and caffeine (r values ranging from 0.906 for
Fremy’s salt assay to 0.968 for DPPH).
Chlorogenic acids (CGA) are water soluble esters formed between trans-cinnamic
acids, such as caffeic acid, and quinic acid. They may be subdivided according to the
nature, number and position of the cinnamic substituents (Clifford, 1999).
Caffeoylquinic acid (CQA) is the most abundant chlorogenic acid class accounting for
76-84% of the total CGA in green coffee (Perrone, Farah, Donangelo, de Paulis, &
Martin, 2008). Although during roasting CGA are lost up to 95%, CQA still are the
predominant CGA in roasted coffee (Trugo & Macrae, 1984). Monocaffeoylquinic acids
(3-CQA, 4-CQA, 5-CQA) and dicaffeoylquinic acids (3,4-diCQA, 3,5-diCQA, 4,5diCQA) were identified and quantified by HPLC-DAD in each fraction and coffee
brew, and the results are shown in Tables 4 and 5. 5-CQA was the major compound
among CQAs in all samples, followed by 4-CQA and 3-CQA. The diCQAs were in
lower concentration than CQAs. The abundance of 3,4-diCQA and 4,5-diCQA was
similar in every coffee fractions or brews, whereas 3,5-diCQA was the least abundant
isomer. These results are in agreement with those reported by other authors in roasted
coffee (Perrone et al., 2008) and in coffee brew (Alves et al., 2010). Higher amounts of
CQA in Robusta coffees than in Arabica ones have been extensively reported (Farah et
al., 2005). However, in this study less amounts of CQA were found in Vietnam coffee
than in Guatemala ones. Also Vignoli et al. (2011) observed higher amount of 5-CQA
in Arabica soluble coffee. This could be due to several factors, such as the origin of
coffee and the higher loss of chlorogenic acids in Robusta coffee during roasting
process (Clifford, 1997; Perrone, Donangelo, Donangelo, & Farah, 2010).
Fractions obtained from espresso coffeemaker showed in both coffees a steep decrease
with extraction time in all three CQA isomers (3-, 4-, and 5-CQA). F1 (0-8s) accounted
for about 70 %, F2 (8-16 s) for 17 % and F3 (16-24 s) for less than 14 % of the total
CQA amounts found in an espresso coffee brew. The CQA extraction behavior was
similar to that of the antioxidant capacity measured by colorimetric assays and Fremy´s
salt, showing high correlations (r values ranging from 0.727 for 5-CQA and DPPH to
0.903 for 4-CQA and Fremy’s salt, p<0.001), maybe because monocaffeoylquinic acids
are the most abundant phenolic compounds in coffee. In contrast, diCQAs were
extracted more slowly, accounting F1 for ~50 %, F2 for ~30 % and F3 still for ~20 %,
showing correlations coefficients lower than 0.700 (except for 3,4-diCQA with r values
ranging from 0.906 for Fremy’s salt to 0.968 for DPPH). The esterification of an
additional caffeic acid moiety in diCQA increases the number of hydroxyl groups and
might favor the retention of these compounds by interaction with melanoidins or other
polymeric compounds (Bekedam, Schols, van Boekel et al., 2008; Kroll, Rawel, &
Rohn, 2003), reducing the release of diCQA. In fact, the hydrogen bonding between
hydroxyl groups of the phenolic compounds and the amide carbonyls of the peptide
bond were found to be a common non-covalent interaction between phenolics and
melanoidins (Nunes & Coimbra, 2010). Also the weaker polarity of the diCQA
compared to the CQA might explain the slower release of these compounds during
extraction with water (Kroll et al., 2003). Blumberg et al. (2010) studied the influence
of hot water percolation on the concentration of monocaffeoylquinic acids and
chlorogenic acid lactones and reported that dicaffeoylquinic lactones were extracted
rather slowly in comparison to monocaffeoylquinic ones.
Caffeoylquinic acids extraction behavior was different in filter coffee, as can be seen in
Table 5. Different extraction profiles were also found for the two coffee samples. In
Guatemala filter coffee, CQAs and diCQAs extraction showed a U-shape profile with
the highest concentration in F1 (0-75 s) and F5 (300-375 s) and the lowest in F3 (150225 s), similar to that observed for antioxidant capacity according to the correlations
showed before. However, in Vietnam filter coffee the U-shape extraction of
caffeoylquinic acids started after 75 s, and F1 exhibited the significantly lowest
caffeoylquinic acids concentration. The delay in caffeoylquinic acids extraction might
be attributed to the longer wetting stage observed in Vietnam coffee, as described
above. On the other hand, the increased extraction of caffeoylquinic acids in the last
stage of the brewing process, mainly observed in F5 in both coffee samples, could be
due to the water pressure decrease that induces a lower flow and a longer contact time
between water and ground coffee. This might facilitate the hydrolysis of caffeoylquinic
acids bound to melanoidins inducing their release during advanced stages of filter coffee
brewing (Lingle, 1996). However, when the lowest volumes of these fractions are
taking into account, it could be observed that caffeoylquinic acids only accounted for
~8 % and ~11 % of the total in Guatemala and Vietnam filter coffee brews, respectively.
Unlike in espresso coffee, similar extraction percentages among CQAs and diCQAs in
each coffee fraction along the filter brewing process were observed. Moreover, when
the concentration of antioxidants is calculated per gram of coffee taking into account the
different fractions volumes, higher extraction of these phenolic compounds per gram of
coffee was obtained in filter coffee brews than in espresso ones, in agreement with
Pérez-Martinez et al. (2010). This may be due to the technological differences between
espresso and filter coffeemaker. Although the high water pressure applied in espresso
coffeemaker favors the extraction process, the short contact time between water and
coffee grounds, the high coffee/water ratio and the limited space in coffee cake does not
allow equilibrium to be reached (Petracco, 2005). In contrast, longer time and
turbulences in the extraction chamber of the filter coffeemaker allow the water in
immediate contact with the coffee to extract additional compounds when it has not
become so saturated with dissolved material. Thus, both technological factors might
favor the extraction of both CQAs and diCQAs, free and bound with melanoidins. In
fact, turbulences are considered, after time and temperature, the third most important
factor in filter coffee brewing (Lingle, 1996). Less turbulences during sequential coffee
percolation could also be the reason why Blumberg et al. (2010) found that
monocaffeoylquinic acids and monocaffeoyl and dicaffeoyl quinides extraction
behaviors were more similar to those of our espresso coffee fractions than filter ones,
i.e. higher extraction in the first fractions and slower release of dicaffeoyl quinides.
In conclusion, brewing time plays a key role in antioxidants extraction of coffee. To
optimize their extraction in order to obtain antioxidants that can be used as ingredients
for functional foods, several technological factors should be taken into account. Thus,
higher water pressure increases antioxidants extraction speed like in the first fraction of
espresso coffee. Nevertheless, parameters like turbulence and longer contact time,
typically of a filter coffeemaker, should be considered in order to increase extraction
efficiency, mainly in less polar antioxidant compounds as diCQA. Moreover, extraction
conditions should also be adjusted for each coffee because cellular structure of coffee
beans may also influence. Further research in the influence of technological parameters
on chemical composition of coffee brew fractions, as well as their sensory properties,
should be needed before to industrial development.
ACKNOWLEDGEMENTS
This research was funded by the Spanish Ministry of Science and Innovation
(AGL2009-12052). We thank the Spanish Ministry of Education (PR2009-0324) and
the Government of Navarra (Dpt. Education and Dpt. Industry) for the grants given to
M.P.P., I.A.L., and L.S.A and the Unión Tostadora for providing the coffee samples.
This study was partially presented at the First International Congress on Cocoa, Coffee
and Tea, September 2011, Novara (Italy), and at the 5th International Conference on
Polyphenols and Health, October 2011, Sitges (Spain).
REFERENCES
Alves (2007). Factors Influencing the Norharman and Harman Contents in Espresso
Coffee. Journal of Agricultural and Food Chemistry, 55(5), 1832-1838.
Alves, R. C., Costa, A. S. G., Jerez, M., Casal, S., Sineiro, J., Nunez, M. J., & Oliveira,
B. (2010). Antiradical Activity, Phenolics Profile, and Hydroxymethylfurfural in
Espresso Coffee: Influence of Technological Factors. Journal of Agricultural and Food
Chemistry, 58(23), 12221-12229.
Aruoma, O. (1999). Antioxidant actions of plant foods: Use of oxidative DNA damage
as a tool for studying antioxidant efficacy. FreeRadicalRresearch, 30(6), 419-427.
Beal, M. (1995). Aging, energy, and oxidative stress in neurodegenerative diseases.
Annals of Neurology, 38(3), 357-366.
Bekedam, E. K., Schols, H. A., Cämmerer, B., Kroh, L. W., van Boekel, M. A. J. S., &
Smit, G. (2008). Electron Spin Resonance (ESR) Studies on the Formation of RoastingInduced Antioxidative Structures in Coffee Brews at Different Degrees of Roast.
Journal of Agricultural and Food Chemistry, 56(12), 4597-4604.
Bekedam, E. K., Schols, H. A., van Boekel, M. A. J. S., & Smit, G. (2008).
Incorporation of Chlorogenic Acids in Coffee Brew Melanoidins. Journal of
Agricultural and Food Chemistry, 56(6), 2055-2063.
Belitz, H. -., Grosch, W., & Schieberle, P. (2009). Coffee, Tea, Cocoa. In H. Belitz, W.
Grosch & P. Schieberle (Eds.), Food Chemistry, (4 th ed.). Berlin: Springer-Verlag.
Bicchi, C. P., Pinello, A. E., Pellegrino, G. M., & Vanni, A. C. (1995). Characterization
of Green and Roasted Coffees through the Chlorogenic Acid Fraction by HPLC-UV and
Principal Component Analysis. Journal of Agricultural and Food Chemistry, 43(6),
1549-1555.
Blumberg, S., Frank, O., & Hofmann, T. (2010). Quantitative Studies on the Influence
of the Bean Roasting Parameters and Hot Water Percolation on the Concentrations of
Bitter Compounds in Coffee Brew. Journal of Agricultural and Food Chemistry, 58(6),
3720-3728.
Borrelli, R. C., & Fogliano, V. (2005). Bread crust melanoldins as potential prebiotic
ingredients. Molecular Nutrition & Food Research, 49(7), 673-678.
Borrelli, R. C., Visconti, A., Mennella, C., Anese, M., & Fogliano, V. (2002). Chemical
characterization and antioxidant properties of coffee melanoidins. Journal of
Agricultural and Food Chemistry, 50(22), 6527-6533.
Brand-Williams, W., Cuvelier, M. E., & Berset, C. (1995). Use of a free radical method
to evaluate antioxidant activity. LWT - Food Science and Technology, 28(1), 25-30.
Caemmerer, B., & Kroh, L. W. (2006). Antioxidant activity of coffee brews. European
Food Research and Technology, 223(4), 469-474.
Clifford, M. (1999). Chlorogenic acids and other cinnamates - nature, occurrence and
dietary burden. Journal of the Science of Food and Agriculture, 79(3), 362-372.
Clifford, M. (1997). The nature of chlorogenic acids: Are they advantageous
compounds in coffee? In: Proceedings 17th International Scientific Colloquium on
Coffee, Nairobi, Kenia, 79-91.
Crozier, A., Jaganath, I., & Clifford, M. (2009). Dietary phenolics: chemistry,
bioavailability and effects on health. Natural Product Reports, 26(8), 1001-1043.
del Castillo, M. D., Ames, J. M., & Gordon, M. H. (2002). Effect of Roasting on the
Antioxidant Activity of Coffee Brews. Journal of Agricultural and Food Chemistry,
50(13), 3698-3703.
Delgado-Andrade, C., Rufian-Henares, J. A., & Morales, F. J. (2005). Assessing the
antioxidant activity of melanoidins from coffee brews by different antioxidant methods.
Journal of Agricultural and Food Chemistry, 53(20), 7832-7836.
Delgado-Andrade, C., & Morales, F. J. (2005). Unraveling the Contribution of
Melanoidins to the Antioxidant Activity of Coffee Brews. Journal of Agricultural and
Food Chemistry, 53(5), 1403-1407.
Devasagayam, T., Kamat, J., Mohan, H., & Kesavan, P. (1996). Caffeine as an
antioxidant: Inhibition of lipid peroxidation induced by reactive oxygen species.
Biochimica et Biophysica acta.Biomembranes, 1282(1), 63-70.
Dorea, J., & da Costa, T. (2005). Is coffee a functional food? British Journal of
Nutrition, 93(06), 773-782.
Farah, A., De Paulis, T., Trugo, L. C., & Martin, P. R. (2005). Effect of Roasting on the
Formation of Chlorogenic Acid Lactones in Coffee. Journal of Agricultural and Food
Chemistry, 53(5), 1505-1513.
Huang, D. J., Ou, B. X., & Prior, R. L. (2005). The Chemistry behind Antioxidant
Capacity Assays. Journal of Agricultural and Food Chemistry, 53(6), 1841-1856.
Kroll, N., Rawel, H., & Rohn, S. (2003). Reactions of plant phenolics with food
proteins and enzymes under special consideration of covalent bonds. Food Science and
Technology Research, 9(3), 205-218.
Lee, C. (2000). Antioxidant ability of caffeine and its metabolites based on the study of
oxygen radical absorbing capacity and inhibition of LDL peroxidation. Clinica Chimica
Acta, 295(1-2), 141-154.
Lingle, T. R. (1996). The Coffee Brewing Handbook. Long Beach, California: Spelcialty
Coffee Association.
López-Galilea, I., Andueza, S., Leonardo, I. d., de Peña, M. P., & Cid, C. (2006).
Influence of torrefacto roast on antioxidant and pro-oxidant activity of coffee. Food
Chemistry, 94(1), 75-80.
López-Galilea, I., de Peña, M. P., & Cid, C. (2007). Correlation of Selected
Constituents with the Total Antioxidant Capacity of Coffee Beverages: Influence of the
Brewing Procedure. Journal of Agricultural and Food Chemistry, 55(15), 6110-6117.
Moreira, D. P., Monteiro, M. C., Ribeiro-Alves, M., Donangelo, C. M., & Trugo, L. C.
(2005). Contribution of Chlorogenic Acids to the Iron-Reducing Activity of Coffee
Beverages. Journal of Agricultural and Food Chemistry, 53(5), 1399-1402.
Natella, F., Nardini, M., Giannetti, I., Dattilo, C., & Scaccini, C. (2002). Coffee
drinking influences plasma antioxidant capacity in humans. Journal of Agricultural and
Food Chemistry, 50(21), 6211-6216.
Nunes, F., & Coimbra, M. (2010). Role of hydroxycinnamates in coffee melanoidin
formation. Phytochemistry reviews, 9(1, Sp. Iss. SI), 171-185.
Perez-Martinez, M., Caemmerer, B., De Pena, M. P., Cid, C., & Kroh, L. W. (2010).
Influence of Brewing Method and Acidity Regulators on the Antioxidant Capacity of
Coffee Brews. Journal of Agricultural and Food Chemistry, 58(5), 2958-2965.
Perrone, D., Donangelo, R., Donangelo, C., & Farah, A. (2010). Modeling Weight Loss
and Chlorogenic Acids Content in Coffee during Roasting. Journal of Agricultural and
Food Chemistry, 58(23), 12238-12243.
Perrone, D., Farah, A., Donangelo, C. M., de Paulis, T., & Martin, P. R. (2008).
Comprehensive analysis of major and minor chlorogenic acids and lactones in
economically relevant Brazilian coffee cultivars. Food Chemistry, 106(2), 859-867.
Peters, A. (1991). Brewing makes the difference. In: Proceedings of the 14th ASIC
Colloquium, San Francisco, USA, pp. 97-106.
Petracco, M. (2005). Percolation. In A. Illy & R. Viani (Eds.), Espresso Coffee: The
Chemistry of Quality, (2 nd ed.) London: Elsevier Academic Press.
Petracco, M. (2001). Technology IV: Beverage Preparation: Brewing Trends for the
New Millenium. In R. J. Clark & O. G. Vitzthum (Eds.), Coffee: Recent Developments.
Oxford, U.K.: Blackwell Science.
Pulido, R., Hernandez Garcia, M., & Saura Calixto, F. (2003). Contribution of
beverages to the intake of lipophilic and hydrophilic antioxidants in the Spanish diet.
European Journal of Clinical Nutrition, 57(10), 1275-1282.
Re, R., Pellegrini, N., Proteggente, A., Pannala, A., Yang, M., & Rice-Evans, C. (1999).
Antioxidant activity applying an improved ABTS radical cation decolorization assay.
Free Radical Biology and Medicine, 26(9-10), 1231-1237.
Roesch, D., Bergmann, M., Knorr, D., & Kroh, L. W. (2003). Structure-Antioxidant
Efficiency Relationships of Phenolic Compounds and Their Contribution to the
Antioxidant Activity of Sea Buckthorn Juice. Journal of Agricultural and Food
Chemistry, 51(15), 4233-4239.
Rufian-Henares, J. A., & de la Cueva, S. P. (2009). Antimicrobial Activity of Coffee
Melanoidins-A Study of Their Metal-Chelating Properties. Journal of Agricultural and
Food Chemistry, 57(2), 432-438.
Rufián-Henares, J. A., & Morales, F. J. (2007). Effect of in vitro enzymatic digestion on
antioxidant activity of coffee melanoidins and fractions. Journal of Agricultural and
Food Chemistry, 55(24), 10016-10021.
Sanchez Gonzalez, I., Jimenez Escrig, A., & Saura Calixto, F. (2005). In vitro
antioxidant activity of coffees brewed using different procedures (Italian, espresso and
filter). Food Chemistry, 90(1-2), 133-139.
Singleton, V., & Rossi, J. (1965). Colorimetry of total phenolics with
phosphomolybdic-phosphotungstic acid reagents. American Journal of Enology and
Viticulture, 16(3), 144-158.
Svilaas, A., Sakhi, A., Andersen, L., Svilaas, T., Strom, E., & Jacobs, D. (2004). Intakes
of antioxidants in coffee, wine, and vegetables are correlated with plasma carotenoids in
humans. The Journal of Nutrition, 134(3), 562-567.
Trugo, L. C., & Macrae, R. (1984). A study of the effect of roasting on the chlorogenic
acid composition of coffee using HPLC. Food Chemistry, 15(3), 219-227.
Variyar, P., Ahmad, R., Bhat, R., Niyas, Z., & Sharma, A. (2003). Flavoring
components of raw monsooned arabica coffee and their changes during radiation
processing. Journal of Agricultural and Food Chemistry, 51(27), 7945-7950.
Vignoli, J. A., Bassoli, D. G., & Benassi, M. T. (2011). Antioxidant activity,
polyphenols, caffeine and melanoidins in soluble coffee: The influence of processing
conditions and raw material. Food Chemistry, 124(3), 863-868.
Table 1. Volumes of coffee brews and fractions obtained by espresso and filter
coffeemakers.
Espresso
Filter
textraction (s)
V (mL)
textraction (s)
V (mL)
24
47
375
532
F1
0-8
16
0-75
80
F2
8-16
14
75-150
146
F3
16-24
17
150-225
186
F4
-
-
225-300
94
F5
-
-
300-375
26
24
46
375
520
F1
0-8
17
0-75
74
F2
8-16
14
75-150
120
F3
16-24
15
150-225
160
F4
-
-
225-300
112
F5
-
-
300-375
54
Guatemala
Coffee brew
Vietnam
Coffee brew
Table 2. pH, browned compounds and caffeine in espresso coffee brews and fractions.
All values are shown as mean ± standard deviation (n=3). Different letters indicate
significant differences (p<0.05) among different coffee fractions in each coffee.
pH
Browned compounds
[Abs420]
Caffeine
[mg/100mL]
4.01 ± 0.01
0.391 ± 0.013
141.4 ± 2.4
F1
4.83 ± 0.01 a
0.903 ± 0.008 c
296.8 ± 1.6 c
F2
4.90 ± 0.01 b
0.253 ± 0.005 b
82.66 ± 0.7 b
F3
5.09 ± 0.01 c
0.128 ± 0.004 a
39.6 ± 0.4 a
5.76 ± 0.00
0.458 ± 0.011
253.3 ± 2.0
F1
5.57 ± 0.01 a
1.172 ± 0.008 c
575.4 ± 3.9 c
F2
6.08 ± 0.01 b
0.297 ± 0.004 b
159.2 ± 0.1 b
F3
6.38 ± 0.00 c
0.133 ± 0.007 a
74.7 ± 0.2 a
Guatemala
Coffee brew
Vietnam
Coffee brew
Table 3. pH, browned compounds and caffeine in filter coffee brews and fractions. All
values are shown as mean ± standard deviation (n=3). Different letters indicate
significant differences (p<0.05) among different coffee fractions in each coffee.
pH
Browned compounds
[Abs420]
Caffeine
[mg/100mL]
Guatemala
Coffee brew
5.29 ± 0.01
0.200 ± 0.003
57.1 ± 0.1
F1
5.12 ± 0.01 a
0.275 ± 0.002 c
106.8 ± 0.1 e
F2
5.25 ± 0.01 b
0.200 ± 0.002 b
57.1 ± 0.2 c
F3
5.39 ± 0.01 c
0.160 ± 0.005 a
35.7 ± 0.0 a
F4
5.37 ± 0.02 c
0.171 ± 0.005 a
48.6 ± 0.4 b
F5
5.12 ± 0.00 a
0.266 ± 0.007 c
89.0 ± 0.6 d
6.07 ± 0.01 x
0.205 ± 0.001
F1
6.14 ± 0.01 c
0.132 ± 0.005 a
65.9 ± 0.6 a
F2
5.93 ± 0.01 a
0.298 ± 0.010 c
158.1 ± 0.3 e
F3
6.06 ± 0.01 b
0.210 ± 0.012 b
112.9 ± 0.2 c
F4
6.19 ± 0.01 d
0.193 ± 0.007 b
104.4 ± 0.8 b
F5
6.08 ± 0.01 b
0.273 ± 0.015 c
117.6 ± 0.9 d
Vietnam
Coffee brew
115.3 ± 0.4
Table 4. Chlorogenic acids in espresso coffee brews and fractions. All values are shown
as mean ± standard deviation (n=3). Different letters indicate significant differences
(p<0.05) among different coffee fractions in each coffee.
3-CQA
[mg/100mL]
4-CQA
[mg/100mL]
5-CQA
[mg/100mL]
3,4-diCQA
[mg/100mL]
3,5-diCQA
[mg/100mL]
4,5-diCQA
[mg/100mL]
43.2 ± 0.1
55.6 ± 0.7
96.7 ± 1.8
5.1 ± 0.1
2.8 ± 0.2
5.0 ± 0.1
F1
91.3 ± 1.3 c
114.6 ± 0.6 c
201.1 ± 1.6 c
9.8 ± 0.2 c
4.2 ± 0.1 c
9.6 ± 0.4 c
F2
26.4 ± 0.4 b
33.8 ± 0.1 b
56.3 ± 0.6 b
6.5 ± 0.4 b
3.1 ± 0.1 b
5.7 ± 0.1 b
F3
15.0 ± 0.0 a
22.4 ± 0.1 a
29.8 ± 0.1 a
3.2 ± 0.0 a
1.8 ± 0.0 a
2.9 ± 0.0 a
25.8 ± 1.2
35.0 ± 0.2
52.9 ± 2.0
4.1 ± 0.0
2.0 ± 0.0
3.8 ± 0.1
F1
49.3 ± 0.6 c
70.4 ± 0.5 c
108.0 ± 2.9 c
7.8 ± 0.2 c
2.7 ± 0.2 c
5.4 ± 0.1 c
F2
16.0 ± 0.1 b
20.5 ± 0.1 b
30.8 ± 0.2 b
4.6 ± 0.0 b
1.7 ± 0.1 b
3.8 ± 0.1 b
F3
9.4 ± 0.3 a
13.0 ± 0.2 a
16.0 ± 0.4 a
2.1 ± 0.0 a
0.8 ± 0.0 a
1.7 ± 0.1 a
Guatemala
Coffee brew
Vietnam
Coffee brew
Table 5. Chlorogenic acids in filter coffee brews and fractions. All values are shown as
mean ± standard deviation (n=3). Different letters indicate significant differences
(p<0.05) among different coffee fractions in each coffee.
3-CQA
[mg/100mL]
4-CQA
[mg/100mL]
5-CQA
[mg/100mL]
3,4-diCQA
[mg/100mL]
3,5-diCQA
[mg/100mL]
4,5-diCQA
[mg/100mL]
17.0 ± 0.1
25.3 ± 0.0
38.7 ± 0.1
3.8 ± 0.0
2.0 ± 0.0
3.2 ± 0.0
F1
31.0 ± 0.3 e
40.9 ± 0.1 d
70.1 ± 0.3 e
6.1 ± 0.3 d
2.9 ± 0.1 c
6.0 ± 0.0 d
F2
16.8 ± 0.4 c
26.2 ± 0.2 c
38.2 ± 0.7 c
3.8 ± 0.1 b
2.0 ± 0.1 b
3.9 ± 0.1 b
F3
11.0 ± 0.1 a
16.8 ± 0.0 a
24.8 ± 0.2 a
2.7 ± 0.1 a
1.4 ± 0.0 a
2.7 ± 0.0 a
F4
14.7 ± 0.2 b
23.0 ± 0.2 b
34.1 ± 0.4 b
3.8 ± 0.2 b
2.1 ± 0.1 b
3.7 ± 0.0 b
F5
24.5 ± 0.8 d
42.0 ± 0.9 d
61.3 ± 1.0 d
4.4 ± 0.0 c
3.0 ± 0.1 c
4.3 ± 0.1 c
15.0 ± 0.1
19.4 ± 0.0
21.8 ± 0.2
3.1 ± 0.0
0.7 ± 0.0
1.2 ± 0.0
F1
10.6 ± 0.2 a
13.1 ± 0.1 a
14.3 ± 0.2 a
2.0 ± 0.0 a
0.3 ± 0.0 a
0.7 ± 0.0 a
F2
18.5 ± 0.2 d
24.4 ± 0.0 e
28.3 ± 0.4 d
4.2 ± 0.1 e
0.9 ± 0.0 d
1.6 ± 0.0 d
F3
14.6 ± 0.1 bc
19.1 ± 0.0 c
21.2 ± 0.2 b
2.9 ± 0.0 c
0.7 ± 0.0 b
1.2 ± 0.0 b
F4
14.5 ± 0.3 b
18.3 ± 0.0 b
20.4 ± 0.5 b
2.8 ± 0.0 b
0.7 ± 0.0 b
1.2 ± 0.0 b
F5
15.2 ± 0.4 c
20.4 ± 0.1 d
22.6 ± 0.6 c
3.6 ± 0.0 d
0.8 ± 0.0 c
1.5 ± 0.0 c
Guatemala
Coffee brew
Vietnam
Coffee brew
FIGURE CAPTIONS
Figure 1. Antioxidant capacity (Folin-Ciocalteau method) of coffee brews and fractions
obtained by espresso (a) and filter coffeemaker (b). All values are shown as mean ±
standard deviation (n=3). ** indicates highly significant differences (p<0.01) between
coffee brews. Different letters indicate significant differences (p<0.05) among coffee
fractions in each coffee.
Figure 2. Antioxidant capacity (ABTS method) of coffee brews and fractions obtained
by espresso (a) and filter coffeemaker (b). All values are shown as mean ± standard
deviation (n=3). ** indicates highly significant differences (p<0.01) between coffee
brews. Different letters indicate significant differences (p<0.05) among coffee fractions
in each coffee.
Figure 3. Antioxidant capacity (DPPH method) of coffee brews and fractions obtained
by espresso (a) and filter coffeemaker (b). All values are shown as mean ± standard
deviation (n=3). ** indicates highly significant differences (p<0.01) between coffee
brews. Different letters indicate significant differences (p<0.05) among coffee fractions
in each coffee.
Figure 4. Antioxidant capacity (Fremy’s Salt method) of coffee brews and fractions
obtained by espresso (a) and filter coffeemaker (b). All values are shown as mean ±
standard deviation (n=3). ** indicates highly significant differences (p<0.01) and ns
nonsignificant differences (p>0.05) between coffee brews. Different letters indicate
significant differences (p<0.05) among coffee fractions in each coffee.
Figure 5. Antioxidant capacity (TEMPO method) of coffee brews and fractions
obtained by espresso (a) and filter coffeemaker (b). All values are shown as mean ±
standard deviation (n=3). ** indicates highly significant differences (p<0.01) and ns
nonsignificant differences (p>0.05) between coffee brews. Different letters indicate
significant differences (p<0.05) among coffee fractions in each coffee.
Figure 1. Antioxidant capacity (Folin-Ciocalteau method) of coffee brews and fractions
obtained by espresso (a) and filter coffeemaker (b). All values are shown as mean ±
standard deviation (n=3). ** indicates highly significant differences (p<0.01) between
coffee brews. Different letters indicate significant differences (p<0.05) among coffee
fractions in each coffee.
a) Espresso coffeemaker
Guatemala
Vietnam
15
c
mg GA/mL
c
10
**
5
b
b
a
a
0
Coffee brew
F1
F2
F3
F1
F2
F3
b) Filter coffeemaker
Guatemala
Vietnam
mg GA/mL
15
10
5
**
d
d
c
a
b
e
c
F2
F3
a
d
b
0
Coffee brew
F1
F2
F3
F4
F5
F1
F4
F5
Figure 2. Antioxidant capacity (ABTS method) of coffee brews and fractions obtained
by espresso (a) and filter coffeemaker (b). All values are shown as mean ± standard
deviation (n=3). ** indicates highly significant differences (p<0.01) between coffee
brews. Different letters indicate significant differences (p<0.05) among coffee fractions
in each coffee.
a) Espresso coffeemaker
Guatemala
Vietnam
150
µmol Trolox/mL
c
c
100
50
**
b
b
a
a
0
Coffee brew
F1
F2
F3
F1
F2
F3
b) Filter coffeemaker
Guatemala
Vietnam
µmol Trolox/mL
150
100
d
50
**
d
e
c
a
b
c
a
b
b
F3
F4
0
Coffee brew
F1
F2
F3
F4
F5
F1
F2
F5
Figure 3. Antioxidant capacity (DPPH method) of coffee brews and fractions obtained
by espresso (a) and filter coffeemaker (b). All values are shown as mean ± standard
deviation (n=3). ** indicates highly significant differences (p<0.01) between coffee
brews. Different letters indicate significant differences (p<0.05) among coffee fractions
in each coffee.
a) Espresso coffeemaker
c
µmol Trolox/mL
60
Guatemala
Vietnam
c
40
**
20
b
b
a
a
0
Coffee brew
F1
F2
F3
F1
F2
F3
b) Filter coffeemaker
Guatemala
Vietnam
µmol Trolox/mL
60
40
20
d
c
**
b
a
b
F2
F3
F4
e
a
d
c
b
F3
F4
0
Coffee brew
F1
F5
F1
F2
F5
Figure 4. Antioxidant capacity (Fremy’s Salt method) of coffee brews and fractions
obtained by espresso (a) and filter coffeemaker (b). All values are shown as mean ±
standard deviation (n=3). ** indicates highly significant differences (p<0.01) and ns
nonsignificant differences (p>0.05) between coffee brews. Different letters indicate
significant differences (p<0.05) among coffee fractions in each coffee.
a) Espresso coffeemaker
c
µmol Trolox/mL
90
c
Guatemala
Vietnam
60
ns
b
30
b
a
a
0
Coffee brew
F1
F2
F3
F1
F2
F3
b) Filter coffeemaker
Guatemala
Vietnam
µmol Trolox/mL
90
60
30
**
c
c
b
a
b
c
b
b
F3
F4
c
a
0
Coffee brew
F1
F2
F3
F4
F5
F1
F2
F5
Figure 5. Antioxidant capacity (TEMPO method) of coffee brews and fractions
obtained by espresso (a) and filter coffeemaker (b). All values are shown as mean ±
standard deviation (n=3). ** indicates highly significant differences (p<0.01) and ns
nonsignificant differences (p>0.05) between coffee brews. Different letters indicate
significant differences (p<0.05) among coffee fractions in each coffee.
a) Espresso coffeemaker
Guatemala
Vietnam
30
µmol Trolox/mL
c
c
20
ns
10
b
b
a
a
0
Coffee brew
F1
F2
F3
F1
F2
F3
b) Filter coffeemaker
Guatemala
Vietnam
µmol Trolox/mL
30
20
10
d
d
c
**
a
b
F3
F4
d
b
b
F3
F4
c
a
0
Coffee brew
F1
F2
F5
F1
F2
F5
Download PDF
Similar pages