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Comparison of nine common coffee extraction methods: Instrumental and sensory analysis

Authors:
  • Eugster / Frismag AG

Abstract and Figures

The preparation of a cup of coffee may vary between countries, cultures and individuals. Here, an analysis of nine different extraction methods is presented regarding analytical and sensory aspects for four espressi and five lunghi. This comprised espresso and lungo from a semi-automatic coffee machine, espresso and lungo from a fully automatic coffee machine, espresso from a single-serve capsule system, mocha made with a percolator, lungo prepared with French Press extraction, filter coffee and lungo extracted with a Bayreuth coffee machine. Analytical measurements included headspace analysis with HS SPME GC/MS, acidity (pH), titratable acidity, content of fatty acids, total solids, refractive indices (expressed in °Brix), caffeine and chlorogenic acids content with HPLC. Sensory analysis included visual, aroma, flavor and textural attributes as well as aftersensation. The technical differences in the extraction methods led to a higher concentration of the respective quantities in the espressi than in the lunghi. Regarding the contents per cup of coffee, the lunghi generally had a higher content than the espressi. The extraction efficiency of the respective compounds was mainly driven by their solubility in water. A higher amount of water, as in the extraction of a lungo, generally led to higher extraction efficiency. Comparing analytical data with sensory profiles, the following positive correlations were found total solids - texture/body, headspace intensity - aroma intensity, concentrations of caffeine/chlorogenic acids - bitterness and astringency.
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ORIGINAL PAPER
Comparison of nine common coffee extraction methods:
instrumental and sensory analysis
Alexia N. Gloess Barbara Scho
¨nba
¨chler Babette Klopprogge
Lucio D‘Ambrosio Karin Chatelain Annette Bongartz
Andre
´Strittmatter Markus Rast Chahan Yeretzian
Received: 5 June 2012 / Revised: 8 January 2013 / Accepted: 10 January 2013 / Published online: 30 January 2013
The Author(s) 2013. This article is published with open access at Springerlink.com
Abstract The preparation of a cup of coffee may vary
between countries, cultures and individuals. Here, an
analysis of nine different extraction methods is presented
regarding analytical and sensory aspects for four espressi
and five lunghi. This comprised espresso and lungo from a
semi-automatic coffee machine, espresso and lungo from a
fully automatic coffee machine, espresso from a single-
serve capsule system, mocha made with a percolator, lungo
prepared with French Press extraction, filter coffee and
lungo extracted with a Bayreuth coffee machine. Analyti-
cal measurements included headspace analysis with HS
SPME GC/MS, acidity (pH), titratable acidity, content of
fatty acids, total solids, refractive indices (expressed in
Brix), caffeine and chlorogenic acids content with HPLC.
Sensory analysis included visual, aroma, flavor and textural
attributes as well as aftersensation. The technical differ-
ences in the extraction methods led to a higher concen-
tration of the respective quantities in the espressi than in
the lunghi. Regarding the contents per cup of coffee, the
lunghi generally had a higher content than the espressi. The
extraction efficiency of the respective compounds was
mainly driven by their solubility in water. A higher amount
of water, as in the extraction of a lungo, generally led to
higher extraction efficiency. Comparing analytical data
with sensory profiles, the following positive correlations
were found total solids $texture/body, headspace inten-
sity $aroma intensity, concentrations of caffeine/chloro-
genic acids $bitterness and astringency.
Keywords Coffee brew Extraction Sensory analysis
Chlorogenic acids Caffeine Headspace analysis
Acidity Fatty acids
Introduction
Since the discovery of coffee as a beverage prepared from
the extract of roasted coffee beans around the fifteenth
century, its popularity has quickly spread around the world
to become one of the most popular beverages of modern
society. During the same period, numerous coffee brewing
and extraction methods were introduced, depending on
geographic, cultural and social context as well as on per-
sonal preferences [1,2]. Extraction methods are generally
characterized by extraction pressure, the extraction process
and tool, and the volume of the extract/cup. Another typical
distinction made in Western societies is between an
espresso and a lungo. Espresso is a concentrated beverage
of 20 ml to 40 ml, brewed by forcing hot water at high
pressure (up to 19 bars) through finely ground coffee and
made for immediate consumption. In contrast, a lungo is a
less intense beverage characterized by a larger cup size
(100 ml up to 250 ml, depending on cultural habits) and
often consumed with milk or cream. There are many ways
Electronic supplementary material The online version of this
article (doi:10.1007/s00217-013-1917-x) contains supplementary
material, which is available to authorized users.
A. N. Gloess (&)B. Scho
¨nba
¨chler B. Klopprogge
L. D‘Ambrosio C. Yeretzian
School of Life Sciences and Facility Management, Institute
of Chemistry and Biological Chemistry, Zurich University
of Applied Sciences, 8820 Wa
¨denswil, Switzerland
e-mail: alexia.gloess@zhaw.ch
K. Chatelain A. Bongartz
School of Life Sciences and Facility Management, Institute
of Food and Beverage Innovation, Zurich University
of Applied Sciences, 8820 Wa
¨denswil, Switzerland
A. Strittmatter M. Rast
Rast Kaffee AG, 6031 Ebikon, Switzerland
123
Eur Food Res Technol (2013) 236:607–627
DOI 10.1007/s00217-013-1917-x
of preparing a lungo: (i) similar to an espresso, extracted
under high pressure, (ii) by pouring hot water on ground
coffee followed by a form of filtering or (iii) by boiling the
water/coffee mixture for a distinct period of time. More
recently, single-serve coffee systems have gained in
popularity.
Consumer preferences for a particular type of coffee
preparation mode may be influenced by various factors
such as culture, lifestyle, social and working environment,
everyday habits and financial considerations and of course
also by flavor preferences [1,2]. More recently, consumer
choices have also been affected by information on the
chemical composition of various types of coffee and the
potential impact of specific components on our health and
well-being.
In the last few decades, intense research on coffee has
expanded our knowledge of the chemical, sensory and
health-related aspects of coffee along the whole value
chain, from the bean to the cup. Furthermore, a few studies
have been published on specific modes of coffee extraction,
in particular on espresso and filter coffee. However, studies
comparing a wide range of popular coffee extraction
methods with respect to chemical and sensory aspects are
rare. The most extensive studies of this type were carried
out by Lo
´pez-Galilea et al. [3,4] and Peters [5]. The former
focused mainly on the antioxidant capacity of different
brews, namely filter coffee, plunger extraction, mocha
extraction and extraction using an espresso machine. Peters
studied dripfilter coffee, the mocha and napolitana system
as well as French Press, percolator and boiled coffee with
respect to their content of dry solids, caffeine, chlorogenic
acids and non-aromatic acids using different types of cof-
fee for the different extraction methods and did not perform
sensory analysis of the different coffee brews.
In this study, we have examined nine extraction meth-
ods—four espressi and five lunghi—using instrumental and
sensory tools to compare a wide range of popular coffee
extraction methods with respect to chemical and sensory
aspects. To the best of our knowledge, there is so far no
study comprising such a big number of extraction methods
evaluated under instrumental and sensory aspects. Giving a
comprehensive chemical and sensory overview of the most
common coffee extraction methods in Europe of nowadays,
this study closes the gap in the literature, focusing mostly
either on analytics or on sensory results, or comparing only
two to three types of extraction methods. In addition, it
reveals that there is not a best extraction method, but every
extraction method has its own characteristics. Beside this
characterization of nine different extraction methods
regarding their chemical composition as well as their sen-
sory characteristics, this study is also aiming at revealing
correlations between instrumentally measured parameters
with sensory-evaluated attributes.
The parameters were chosen so that many important
quality criteria for a good cup of coffee were covered. They
are the following: The first impression of a cup of coffee is
visual related to the crema, the color and the volume. The
next impression is the aroma perceived ortho-nasally and
measured via analysis of the headspace of the coffee brew
[68]. More than 1,000 volatile organic compounds
(VOCs) have so far been identified in the gas phase of
coffee, yet only a fraction is odor active, and around 20 are
key aroma compounds, that is, are relevant for a typical
coffee aroma [911].
The next impression is the flavor, which corresponds to
a combination of retro-nasal aroma impression and taste. A
well-balanced acidity interacting with a fruity and roasty
note, rounded by a slight, coffee-like bitterness, is often
considered to be a good coffee flavor. In this overall
impression, the acidity of the brew is a particularly
important criterion for a good cup of coffee. One part of
this study was to evaluate the influence of the extraction
method on the acidity of the brews. From an instrumental
point of view, we measured the pH value as well as the
titratable acidity up to a pH of 6.6, corresponding
approximately to the pH in the mouth when drinking cof-
fee, and up to a pH of 8.0, where the weaker organic acids
in the coffee brew are also covered [12].
The body, also called mouth-feeling or texture, is a fur-
ther important sensory descriptor for coffee. From an
instrumental perspective, it is often related to the total solids
and occasionally also linked to fat or fatty acid content.
Furthermore, for sustained sensation at the end of a sip, the
finishing should be well balanced between the aroma,
acidity, bitterness and astringency. The contents of caffeine
and chlorogenic acids are said to be important factors for the
salubriousness of coffee. The latter are degrading during the
roasting process [2,1317]. However, they are known to be
important antioxidants and are active even at concentrations
as low as 10 lg/ml of 5-CQA [15,18]. However, at higher
concentrations, the chlorogenic acids are said to cause acid
reflux symptoms, together with other compounds [15]. Both
caffeine and chlorogenic acids are often mentioned in con-
junction with bitterness. Astringency may correlate to the
concentration of chlorogenic acids in the brew [19],
although the molecules causing the astringent feeling may
not be those of chlorogenic acids [20].
Materials and methods
General
The same coffee was used for all extractions (Guatemala
Antigua LA CEIBA), except for the single-serve capsules
(Nespresso/Arpeggio capsules). Green beans were roasted
608 Eur Food Res Technol (2013) 236:607–627
123
at RAST Kaffee, Ebikon, Switzerland, to a roast degree of
Pt 80 (Colorette, 3b, PROBAT-WERKE, Emmerich am
Rhein, Germany) for espresso and Pt 86 for lungo, packed
in 1-kg airtight bags (laminate with a metallized film, with
valve) and stored at room temperature before use
(1–2 weeks). The different roast degrees chosen here may
imply a different composition of chlorogenic acids, but
they are closer to a typical consumer’s situation. Local tap
water was mixed with filtered water (PURITY 600 Quell
ST, BRITA Professional, Taunusstein, Germany) to adjust
the extraction water to 4–6dH (German water hardness).
The milling degree as well as the amount of ground coffee
were optimized for each brewing type and are described in
the following. For grinding, an Espresso Grinder (KED
640, Ditting, Bachenbu
¨lach, Switzerland, milling degree
1=finest to 8 =coarse) as well as a retail grinder (KR
805, Ditting, Bachenbu
¨lach, Switzerland, milling degree
1=finest to 8 =coarse) were used. The coffee was
always freshly ground before coffee extraction (except for
the single-serve capsule system). The particle size distri-
butions of the coffee powder ground on the Ditting grinders
are given in Analytical Techniques—Particle size of
ground coffee. For the coffee ground on the fully automatic
coffee machine (with integrated grinder), and the pre-
ground coffee for the single-serve capsule system, no
particle size distribution was measured. The milling degree
of the fully automatic coffee machine was set by the
service technician to optimize the extraction time. The
main extraction parameters are summarized in Table 1.
These were optimized for each brewing method, keeping as
many parameters as possible constant while trying to
reflect a typical extraction of coffee of a consumer. For
each brewing type, the first extraction was discarded. Three
samples per extraction type were prepared, and each was
analyzed in triplicate. Most samples were measured on two
different days.
Coffee extraction
Nine different extraction methods were examined, com-
prising four espressi and five lunghi.
Espresso from semi-automatic machine(DE) A Dalla
Corte Evolution 20.03 with two brewing units was used
(Rogalla—Dalla Corte Schweiz, Switzerland). Three cof-
fee samples were prepared, each combining five freshly
brewed double espressi, resulting in 300 ml per sample.
Lungo from semi-automatic machine(DL) A Dalla
Corte Evolution 20.03 was used (as above). Per sample,
two extractions were combined to 480 ml.
Espresso from fully automatic machine(SE) The set-
tings of the fully automatic coffee machine Schaerer Cof-
fee Celebration BC (Schaerer, Switzerland) were chosen so
that per brew two espressi a
`30 ml were extracted in
25.3 ±0.7 s (n=15, 95 %) at a pressure of 8.25 bar and
Table 1 Details of the extractions: the extraction method (for
abbreviations—see text), the roast degree in Pt (measured with
Colorette 3b, Probat), the milling degree and the amount of ground
coffee per extraction in grams, the volume of water per cup or jug in
milliliters, the extraction time in seconds, the extraction temperature
in degrees centigrade, and the extraction pressure in bar are given
Extraction
method
Roast
degree
Milling degree Ground coffee
per extraction
Volume of extract
per cup or jug
Extraction
time
Extraction temperature,
extraction pressure
Pt KED 640 KR 805 g ml s C, bar
DE 80 3.0 (DE1) between 2.5 and
2.75 (DE2, DE3)
16.01 ±0.01
a
2930 28.7 ±0.2
a
92 C, 9 bar
DL 86 7.25 (DL1) 7.5 (DL2, DL3) 16.01 ±0.01
a
29120 37.2 ±0.3
a
92 C, 9 bar
SE 80 –
b
16.0 ±0.6
c
2930 25.3 ±0.3
a
90 C
d
, 8.25 bar
SL 86 –
b
16.0 ±0.6
c
29120 35.3 ±0.1
a
90 C
d
, 7.5 bar
Bia 86 Between 2.5 and 2.75 7.5 ±0.1
a
110 224 ±12
a
n.n.
NE – –
b
5.5 ±1.1
a
30 24 ±2
a
n.n./19 bar
e
F 80 8.0 100.02 ±0.03
a
1,800 348 ±2
a
ca. 90 C, 1 bar
KK 80 8.0 27.500 ±0.003
a
500 370 ±10
a
ca. 90 C, 1 bar
Bo 80 8.0 27.493 ±0.003
a
500 240 ±2
a
ca. 90 C, 1 bar
a
Standard deviation of the mean
b
Information not provided by the manufacturer. For SE and SL, the milling degree was set by the service technician to optimize the extraction
time
c
The amount of ground coffee was regulated in the initial setting of the machine, together with the service technician; the error is an estimated
value
d
Corresponds to the temperature of the boiler. The exact extraction temperature is not defined
e
Information provided by the manufacturer
Eur Food Res Technol (2013) 236:607–627 609
123
a temperature of ca. 90 C. The amount of ground coffee
per 30 ml was about 8 g Guatemala Pt 80. Five extracts
were combined, resulting in 300 ml per sample.
Lungo from fully automatic machine(SL) was brewed
on the above-mentioned Schaerer Coffee Celebration BC.
At an extraction temperature of circa 90 C and a pressure
of 7.5 bar, two cups a
`120 ml were extracted in
35.3 s ±0.2 s (n=6, 95 %) (circa 8 g roast and ground
Pt 86 per cup). For each sample, two extracts were
combined.
EspressoNespresso (NE) samples were prepared from
10 espresso capsules (circa 30 ml extracts) of the variety
‘Arpeggio’’ (Nestle
´Nespresso, Switzerland) on a Nes-
presso machine (Turmix TX 170 CitiZ Steel Gray, DKB
Household Switzerland AG, Switzerland).
EspressoBialetti (Bia) An espresso maker, Moka
Express, designed for three cups (Bialetti, Coccaglio, Italy)
was used. Three extracts a
`110 ml were combined per
sample.
LungoFrench Press (Bo) extraction was prepared with a
double-wall coffee maker Shin Bistro (Bodum, Switzerland).
LungoKarlsbader Kanne (KK) was extracted on a
preheated Bayreuth coffee maker using the traditional
Karlsbad method (Erste Bayreuther Porzellanfabrik Walk-
u
¨re Siegmund Paul Meyer GmbH, Germany). For brewing,
500 ml of boiled water (ca. 90 C) was poured in small
portions onto the ground coffee and reheated in between.
LungoFilter Coffee (F) was brewed using a paper
filter and a coffee machine from Hapag Aarau (HAPAG
AARAU Mod. A140, HAPAG AG, Switzerland).
Analytical techniques
Total solids A total of 10 g of coffee extract was dried at
105 C until constant weight (less than ±0.5 mg). The
refractive index of the coffee brews was measured at 20 C
(refractometer AB-1, Kru
¨ss, Germany) and converted to
Brix values according to [21].
pH and titration The pH of each sample was measured
at 20 C. A total of 40 ml of coffee brew was titrated with
0.1 M NaOH at 20 C to (i) a pH of 6.6 and (ii) a pH of 8.0
(Titrando 809, Metrohm, Switzerland).
Headspace-SPME-GC/MS A total of 10 ml of coffee
extract was analyzed immediately after preparation with
headspace–solid-phase micro-extraction–gas chromatogra-
phy/mass spectrometry (HS SPME-GC/MS). A poly-
dimethyl-siloxane/divinylbenzene (PDMS/DVB) SPME
fiber with a 65-lm-thick film (Supelco, Sigma-Aldrich
Chemie GmbH, Switzerland) and a DB-WAX (30 m 9
250 lm90.25 lm) column (Agilent Technologies,
Switzerland) were used. The time temperature profile was
chosen as follows. SPME parameters (Gerstel, Switzer-
land): incubation: 4 min at 50 C, agitating at 250 rpm;
extraction time: 7 min at 50 C; desorption time: 5 min at
240 C; GC/MS parameters (7890/5975 N, Agilent Tech-
nologies, Switzerland):35C for 1 min, then 4 C/min to
100 C for 10 min, followed by 30 C/min to 130 C for
8 min, and finally 6 C/min to 220 C for 5 min; split less
mode; flow 1 ml/min; EI source 70 eV, 230 C; detector
150 C. For data analysis, the software MSD Chemstation
(Version G1701 EA E.02.00.493, Agilent Technologies,
Switzerland) and the database NIST08 were used. Chemi-
cal identification was performed via the respective mass
spectrum and retention time. A typical chromatogram is
shown in Fig. 1. More than 100 compounds were identi-
fied, and 38 molecules contributing to the aroma of coffee
were chosen to evaluate the headspace of the respective
coffee brew extraction methods (see Electronic Supple-
mentary Material, Supp. Table 1) [911,2229]. Their
integrated intensities are summed up to the total headspace
intensity which is compared here for the different extrac-
tion types.
Analysis of fatty acids The coffee extract was transe-
sterificated according to the method 269.1 in the Schwe-
izerisches Lebensmittelbuch [30]. In brief, 15 g of coffee
extract and 500 ll recovery standard (50 mg glyceryl
tridecanoat in 10 ml dioxan) were adsorbed on an Extre-
lut
NT 20 column (VWR International AG, Switzerland).
With diethyl ether (Sigma-Aldrich Chemie GmbH,
Switzerland), the nonpolar compounds were washed out.
Diethylether was evaporated and 4.5 ml dioxan (Sigma-
Aldrich Chemie GmbH, Switzerland) and 500 ll internal
standard (50 mg methyl nonanoate, 50 mg glyceryl triun-
decanoate and 50 mg tetradecen in 10 ml dioxan) were
added to the residuum and mixed with 5 ml of 5 % sodium
methylate—methanol solution. After 1 min, the transeste-
rificated coffee oil was extracted with 15 ml heptane and
10 ml aqueous disodium hydrogen citrate solution (Sigma-
Aldrich, Switzerland).
Fig. 1 HS SPME GC/MS chromatogram of Bia11 as an example of a
typical chromatogram. The intensity in abundance (10
6
9total ion
current) is plotted against the retention time in minutes
610 Eur Food Res Technol (2013) 236:607–627
123
The resulting fatty acid methyl esters (FAME) were
analyzed with GC/MS, a typical chromatogram is shown in
Fig. 2. A total of 1 ll of the organic phase was injected
into the GC/MS (Agilent 6890 (GC), 7683 (injector),
5973 N (MS), Agilent Technologies, Switzerland). GC/MS
parameters: Injection was performed with a split of 5.2:1 at
250 C. The oven was kept at 70 C for 2 min and then
heated with 6 C/min to 240 C and kept for 10 min at
240 C. A capillary column HP-FFAP (30 m 9250 lm
90.25 lm, Agilent Technologies, Switzerland) was
chosen with a constant helium flow of 2 ml/min. For
data analysis, the software MSD Chemstation (Version
D.03.00.611, Agilent Technologies, Switzerland) and the
database NIST08 were used.
This method analyzes only the esterified fatty acids in
the coffee extracts, and not the free fatty acids, as they are
most probably retained on the Extrelut
NT 20 column.
Since most of the fatty acids in coffee are esterified, the
majority as triglycerides and a few as diterpene esters or
sterol esters [3133], this analysis closely reflects the
composition of fatty acids in the coffee extracts.
Chlorogenic acids and caffeine content 2 g coffee
extract, 500 ll Carrez I (30 % aqueous ZnSO
4
solution),
500 ll Carrez II (15 % aqueous potassium hexacyano (II)
ferrate trihydrate) and 500 ll methanol were diluted with
distilled water up to 25 ml and filtered with filter paper
(Faltenfilter LS 171/2, D=150 mm, Schleicher & Schu-
ell, Germany) and a syringe filter (Chromafil Xtra PET-45/
25, Macherey–Nagel, Switzerland). Quantitative analyses
were performed using an Agilent Series 1200 HPLC,
equipped with an Agilent Eclipse Plus C18 1.8 lColumn
(100 mm 92.1 mm i.d., thermostat at 20 C) and a diode
array detector. Mobile Phase A was water (containing
0.1 % formic acid) and mobile phase B was acetonitrile
(containing 0.1 % formic acid). The gradient mode is
1 min with 5 % mobile phase B, then 10 min with 25 % of
B and finally 50 % of B for 20 min. The flow rate was
0.35 ml/min. The detector was set at 325 nm for chloro-
genic acids and 272 nm for caffeine. The injection volume
was 3 ll. Substances were identified by comparing their
retention times to those of the respective standards. Typical
chromatograms are shown in Fig. 3. Concentrations of
3-CQA, 5-CQA and caffeine were calculated using the
regression equation of external standards and corrected
with the recovery rate. No commercial standard was
available for 4-CQA while conducting these measurement;
hence, it was not quantified here. 5-O-caffeoyl quinic acid
(5-CQA) was obtained from Chengdu Biopurify Phyto-
chemicals, China, caffeine from Sigma-Aldrich Chemie,
Switzerland, and 3-O-caffeoyl quinic acid (3-CQA) from
Acros Chemicals, Switzerland.
Particle size of ground coffee The particle size distri-
butions of the respective milling degrees 3 and 7 of
Espresso Grinder KED 640 (Ditting, Switzerland) and of
milling degree 8 of the retail grinder KR 805 (Ditting,
Switzerland) were analyzed with laser diffraction at
DELICA AG (Switzerland). The results were as follows:
KED-3: 400 lm at maximum of size distribution (max),
220 lm at the full width of half-maximum (FWHM);
KED-7: 600 lm max, 250 lm FWHM; KR805-8:
1,000–1,025 lm max, 280 lm FWHM.
Sensory evaluation was performed by a trained sensory
panel of seven panelists, in accordance with DIN 10967-2
(profiling based on consensus). The temperature and
humidity conditions as well as the serving temperatures of
Fig. 2 GC/MS chromatogram of the FAME analysis of Bia22 as an
example of a typical chromatogram. The intensity in abundance
(10
6
9total ion current) is plotted against the retention time in
minutes. 1C18 octadecanoic acid methyl ester, 2C18:1 octadecenoic
acid methyl ester, 3C18:2 octadecadienoic acid methyl ester, 4C18:3
octadecatrienoic acid methyl ester, 5C20 eicosanoic acid methyl ester
and 6C22 docosanoic acid methyl ester
Fig. 3 Typical HPLC
chromatograms of acaffeine at
272 nm and bchlorogenic acids
at 325 nm in a coffee extract.
The detector response in
absorption units (mAU) is
plotted against the elution time
in minutes. 1Caffeine, 2
5-CQA, 33-CQA
Eur Food Res Technol (2013) 236:607–627 611
123
the extractions are given in Table 2. Each extraction
method was analyzed in duplicate. The coffee was prepared
fresh before analysis. The serving temperatures were
measured on randomly chosen cups of coffee with a digital
thermometer (type 106, -50 Cto?275 C, Testo AG,
Switzerland). The differences in the serving temperatures
are inherent in the extraction methods. In principle, dif-
ferences in the serving temperature may influence the
sensory perception of, for example, acidity. Eighteen sen-
sory attributes divided into five categories (see Table 3)
were evaluated on a scale from ‘‘0 =not perceivable’’ to
‘‘5 =very strong.’’ Regarding the sensory attributes acid-
ity and astringency, one has to keep in mind that acidity is a
basic taste in the mouth, whereas astringency is a tactile
sensation best described by a rough, dry mouth-feeling,
evoked by chemical stimuli. The attributes in the flavor
correspond to the sensation when the coffee still is in the
mouth. The attributes in the aftersensation correspond to
the sensation when the coffee is already spit out or swal-
lowed. In the case of the attributes crema—fineness, the
scale was ‘0 =rough-porous’ to ‘5 =fine-porous,’’ in
the case of crema—color, the scale was ‘‘0 =clear brown’’
to ‘‘5 =dark brown,’’ and in the case of crema—quantity,
the scale was ‘‘0 =small amount’’ to ‘‘5 =huge amount.
To neutralize the panelists’ pallets between the tastings of
different extracts, water and crackers (Jacob‘s Cream
Crackers) were available.
Principal Component Analysis (PCA) The PCA was
performed with the software XLStat (version 2010.4.06).
All attributes, chemical or sensory, were included in the
PCA, which was calculated based on the Pearson correla-
tion matrix. All data were auto-scaled before use.
Results and discussion
The purpose of this study was to compare different types of
coffee extraction methods and to correlate analytical mea-
surements with sensory evaluation. To the best of our
knowledge, this is the first study applying such a large and
consistent range of instrumental and sensory methods and
covering so wide a range of coffee extraction methods. The
nine extraction methods (four espressi and five lunghi)
analyzed in this study are the following: a semi- and a fully
automatic coffee machine, a single-serve capsule system,
mocha made with a percolator, a French Press (also called
Plunger Pot), filter coffee (paper filter) and a Bayreuth
coffee machine (traditional Karlsbad method). The extrac-
tion parameters were optimized for each brewing method to
be as close as possible to settings used by consumers while
guaranteeing the best possible comparability.
Instrumental results are presented from three perspec-
tives: Firstly, results are presented from the perspective of
having a sip of coffee, approximated as a 10-ml volume of
coffee brew. This reflects a typical consumer’s viewpoint
and the situation of sensory evaluation by the panel. Sec-
ondly, the content of a full cup of coffee, namely 30 ml for
espresso and 120 ml for lungo, is presented, to point out the
difference between the concentration of ingredients in a sip
of coffee and the total content of ingredients in a whole cup
of coffee. In particular, in some medicinal aspects, but also
for the sensory perception, it is important to differentiate
between the concentration of a specific compound and the
total content of a specific compound in a cup of coffee.
Thirdly, the extraction efficiency for the various coffee
constituents is given. Fourthly, the sensory point of view is
presented, before the advantages and shortcomings of the
respective extraction types are summarized. Finally, the
sensory results are compared to instrumental measurements.
From the instrumental point of view, we analyzed the
headspace of the brew by headspace—solidphase micro-
extraction—gas chromatography/mass spectrometry (HS
SPME-GC/MS), the acidity (pH value), the titratable
acidity up to pH 6.6 and pH 8.0, the content of fatty acids
Table 2 Serving conditions of the extracts on the two different testing
days, including the room temperature in degrees centigrade (C), the
relative humidity in percent (%) as well as the serving temperature in
degrees centigrade (C) for the respective extraction methods
Day 1 Day 2
Room
temperature
21.5 C Room
temperature
21.6 C
Relative
humidity
43.2 % Relative
humidity
35.8 %
Extraction
method
Serving
temperature
Extraction
method
Serving
temperature
KK 60.9 C F 63.9 C
Bo 69.9 C DL 67.9 C
SL 69.6 C DE 64.2 C
SE 63.9 C NE 68.3 C
Bia 68.1 C
Table 3 Sensory attributes in the categories: optic of crema, aroma,
flavor, texture and aftersensation
Optic of
crema
Aroma Flavor Texture Aftersensation
Quantity Overall
intensity
Fruity Body Aroma
Fineness Fruity Cereal/
nuts
Acidity
Color Cereal/nuts Roasty Bitterness
Roasty Sweetness Astringency
Acidity
Bitterness
612 Eur Food Res Technol (2013) 236:607–627
123
with GC/MS, the content of total solids (by gravimetry),
the Brix value (via refractive index) and the content of
caffeine and chlorogenic acids (3-CQA, 3-O-caffeoyl
quinic acid and 5-CQA, 5-O-caffeoyl quinic acid) with
high-performance liquid chromatography (HPLC). The
4-O-caffeoyl quinic acid (4-CQA) is an important constit-
uent of the coffee brew, also, but for technical reasons, we
were not able to quantify 4-CQA in this project (for further
details see Materials and Methods).
Sensory analysis included the following attributes: optic
of crema (quantity, fineness, color), aroma (overall inten-
sity, and fruity, cereal/nuts and roasty attributes), flavor
(fruity, cereal/nuts, and roasty attributes, sweetness, acid-
ity, bitterness), texture (body) and aftersensation, also
called ‘‘finishing’’ (aroma, acidity, bitterness, astringency),
comprising 18 sensory attributes in total.
Content per sip of coffee
In Fig. 4, the results with respect of the content of the
total solids, the Brix values, the pH values and the
titratable acidity, the results for headspace intensity, fatty
acid content, caffeine and chlorogenic acids for the
respective extraction methods are given per 10 ml of
coffee extract, which corresponds to the amount of coffee
brew in one sip. In the Electronic Supplementary Mate-
rial, this information is given also in table form (Supp.
Table 2). In most cases, the espressi show higher
concentrations than the lunghi.
Total solids, refractive index and Brix The espressi DE,
SE and NE had a content of total solids of above 4 %,
which is typical for an espresso and considered a pre-
requisite for a good espresso by barista [2]. Extraction with
the Bialetti led to a smaller content of 2.13 % ±0.01 %,
which is, strictly speaking, too low for an espresso. How-
ever, it should be borne in mind that, while this extraction
method is generally considered to be an espresso method,
the ratio of water to ground coffee is closer to that of a
lungo (110 ml water to 7.5 g ground coffee). In the case of
the lunghi, the content of total solids was slightly more
than one percent. The highest value was found for the
French Press (1.43 % ±0.01 %); the lowest, as expected,
for the filter coffee extract (1.03 % ±0.01 %).
The total solids content correlated almost linearly with
the refractive index and, hence, with Brix. In fact, it is
interesting that the Brix value was found to be linked to a
large number of instrumental and sensory attributes. In this
study (based on one single type of coffee), a positive cor-
relation of the refractive index (Brix) with the following
attributes was observed: concentration of total solids,
headspace intensity, concentration of caffeine, 3-CQA and
5-CQA, and titratable acidity. Furthermore, these attributes
were greater with an increase in the following sensory
attributes: aroma intensity, body, roasty flavor, bitter fla-
vor, bitterness and astringency in aftersensation.
Acidity and titration NE was the most acidic brew (pH
5.51), the acidity decreasing (pH increasing) from filter
coffee to Karlsbader Kanne, Schaerer Espresso, Schaerer
Lungo, Dalla Corte Lungo, Dalla Corte Espresso, Bialetti
and, finally, French Press (pH 5.92). There was no differ-
ence between espresso and lungo extract, so that the
different roast degrees for lungo and espresso seem to have
had no influence on pH. The lower roast degree of lunghi
(which may preserve acids) might have compensated for
the higher dilutions. The results are consistent with the
literature [3,5,15,3437].
In respect of titratable acidity, titration needs to be
performed with a much higher volume of NaOH in an
espresso than in a lungo to reach the specific value pH
(6.6 or 8), irrespective of the pH value of the brew itself.
Headspace-SPME-GC/MS The headspace intensity
decreased steadily from DE and SE to Bia and the lunghi.
There are two possible explanations for this observation.
Firstly, the lungo had a higher ratio of water to coffee,
leading to lower overall concentrations in the coffee solu-
tion and therefore also to lower concentrations of the aroma
molecules in the gas phase above the cup. Secondly, the
preparation of a lungo took longer, during which the highly
volatile aroma molecules were able to evaporate. As the
lunghi made with the Dalla Corte and the Schaerer
machines had a similar headspace intensity to the other
lunghi (French Press, Karlsbader Kanne, filter coffee)
while having a much faster extraction time (35–37 s vs.
4–6 min, respectively), the influence of the extraction time
seemed to be minor in comparison with the dilution effect.
Content of fatty acids The content of esterified fatty
acids in the respective coffee brews was very low (below
0.2 w-%) in all cases. The French Press extraction showed
the highest percentage, resulting from the ground coffee
having relatively long contact with hot water, and was
perceivable as a film of fat covering the walls of the glass
jar. Filter coffee showed the lowest content of fatty acids,
as the paper filter appeared to contain them. In Fig. 5, the
composition of the esterified fatty acids is shown. Hexa-
decanoic and octadecadienoic acids amounted to more than
80 % of the fatty acids in total.
Speer and Ko
¨lling-Speer [31] reviewed the literature on
the lipid fraction of the coffee bean, focusing on the green
bean. Roasting seems to have a minor influence on the
composition of the fatty acids. Concerning the brew, they
reported a higher amount of total lipids for espresso than
for filter coffee [31,38]. Ratnayake et al. [33] also report a
much higher concentration of lipids in espresso (2,260 mg/
L) than in metal screen-filtered coffee (335 mg/L) and
drip-filtered coffee (13 mg/L). Other authors, for example,
Jham et al. [39], Martı
´n et al. [40] and Carisano and
Eur Food Res Technol (2013) 236:607–627 613
123
Gariboldi [41], found similar results for fatty acids in
ground coffee concerning content and composition of fatty
acids.
Caffeine The highest concentration of caffeine per sip of
coffee was measured in the espressi, with DE containing
the highest concentration ((21.0 ±0.4) mg/10 ml) per sip.
Fig. 4 Content per 10 ml
extract prepared according to
the different extraction methods
(DE, SE, NE, Bia, DL, SL, Bo,
KK and F) of (a) total solids in
weight percent (TS/w. %),
(b)Brix, (c) pH value, (d) total
headspace intensity in area
counts (intensity/counts),
amount of 0.1 M NaOH for
titration to (e) pH 6.6 and
(f) pH 8 in milliliters (ml 0.1 M
NaOH), (g) fatty acids in weight
percent (fatty acids/w. %),
(h) caffeine in milligrams
(caffeine/mg), (i) 3-O-caffeoyl
quinic acid in milligrams
(3-CQA/mg) and
(j) 5-O-caffeoyl quinic acid in
milligrams (5-CQA/mg). The
error bars correspond to the
standard deviation of the mean
(s95 %)
614 Eur Food Res Technol (2013) 236:607–627
123
Caffeine concentration decreased from SE, NE, Bia to the
lunghi DL, SL, and Bo, KK and FF, the latter showing the
lowest content per sip of (4.7 ±0.1) mg/10 ml.
In case of the caffeine concentrations, Lo
´pez-Galilea
et al. [3,4] found slightly lower values for the caffeine
content of espresso, mocha, French Press and filter coffee,
whereas Peters [5] found slightly higher values for the
caffeine concentration for dripfilter coffee, mocha, napol-
itana and French Press, stating that the caffeine content
seems to be a function of the type of coffee used. As Peters
did not specify the coffee used for extraction, and as he
used different types of coffee for the different extraction
methods, the results cannot be compared directly to the
results presented here.
Chlorogenic acids In the case of the chlorogenic acids, it
was again the espressi that had the highest concentrations,
whereas Bia, DL, SL and the filter methods all showed a
lower concentration. The values ranged from (1.83 ±0.05)
mg/10 ml (F) to (5.8 ±0.2) mg/10 ml (DE) for 3-CQA
and from (0.78 ±0.04) mg/10 ml (KK) to (2.8 ±0.2) mg/
10 ml (DE) for 5-CQA, which is consistent with values in
the literature [5,18,4244].
In contrast to the lower caffeine concentrations reported
by Lo
´pez-Galilea et al. [3], they reported higher 5-CQA
values, which may be due either to the Arabica/Robusta
blend they used for extraction or to the roast degree of the
coffee. Ludwig et al. [37] studied the influence of brewing
time on the extraction of antioxidants for espresso and filter
coffee and found similar concentrations for caffeine and
chlorogenic acids as reported here.
The work of Balakrishnan Nair et al. [45] confirms the
results of the presented study, also. They studied the effect
of brewing type and the coffee to water ratio on the content
of total solids, caffeine and 3-CQA for espresso made with
a percolator, espresso extracted with a commercial type of
machine and extraction via steeping. In the case of 3-CQA,
they report higher concentrations, which may be due to the
coffee they used. Unfortunately, they did not specify the
coffee they used.
In general, the concentration of the respective compo-
nents in the brew was highest for espressi, followed by the
mocha extraction and the lunghi. The smaller concentration
of the compounds in the lunghi with respect to the espressi
seemed to be stemming from the differences in the ratios of
water to coffee, or in other words, the lunghi were more
diluted than the espressi. The extraction time and pressure
seemed to have only minor influence, as the lunghi pre-
pared with the fully and semi-automatic coffee machines
(short time, high pressure) showed similar concentrations
as the lunghi from the infusion methods (long time, low
pressure).
The results presented in this study are in accordance
with the results presented by Lo
´pez-Galilea et al. [3,4] and
Peters [5]. Concerning the pH and the content of total
solids, Lo
´pez-Galilea et al. and Peters found similar values,
except for the mocha extraction, where Peters found a
higher content of total solids caused by a higher coffee to
water ratio. They both confirmed a higher headspace
intensity for the espresso extraction, mocha and napolitana
than for filter coffee and French Press, as did Rocha et al.
[46] and Zahm et al. [47].
Several research groups have so far studied the influence
of the brewing time and the ratio of water to coffee on the
extraction of the constituents of coffee [4754], showing
that most of the water extractable components are washed
out in the first few seconds of the extraction process under
high pressure. Exceptions are less water-soluble com-
pounds, like 5-CQA or isoflavones, in consistency with the
findings of this study. This rapid extraction of the com-
ponents may explain the higher concentration of the coffee
constituents in an espresso compared to a lungo.
Content per cup of coffee
The content of the different quantities per cup of coffee
(30 ml espresso, 120 ml lungo) is shown in Fig. 6and in
the Electronic Supplementary Material (Supp. Table 3). As
the Brix, pH and headspace intensity are intensive values,
there is no differentiation between a sip and a cup. They are
therefore not included here.
While the contents per sip showed generally higher
concentrations in an espresso compared to a lungo, the
situation was often different when considered per cup. Per
cup of coffee, the lunghi generally contained just as much
of the various components analyzed as the espressi, if not
more. However, Bia was often found to be an exception.
When consumed as an espresso, with a cup size of 30 ml, it
Fig. 5 Composition of the content of the esterified fatty acids of the
respective coffee brews in percentage of the total amount of fatty acid
methyl esters in the chromatogram. C16: hexadecanoic acid methyl
ester, C18: octadecanoic acid methyl ester, C18:1: octadecenoic acid
methyl ester, C18:2: octadecadienoic acid methyl ester, C18:3:
octadecatrienoic acid methyl ester, C20: eicosanoic acid methyl ester,
C22: docosanoic acid methyl ester, C24: tetracosanoic acid methyl
ester. The error bars correspond to the standard deviation of the mean
in the 95 % CI
Eur Food Res Technol (2013) 236:607–627 615
123
is indeed prepared more like a lungo in terms of the water
to coffee ratio (also called the draw-off ratio; see Table 1).
Yet, assuming a cup size of 120 ml, the amount of the
respective component per cup would be four times higher.
Total solids Per cup of coffee, no significant difference
was found in total solids between an espresso and a lungo.
Acidity and titration Lunghi were found to have a higher
content of titratable acids per cup than espressi. The low
value for the Bia extract was striking, which may be
explained by the low draw-off ratio.
Content of fatty acids The content of fatty acids per cup
of coffee was very low, especially in the case of filter
coffee ((0.0010 ±0.0002) g/cup). A clear maximum was
shown by Bo extraction ((0.19 ±0.03) g/cup). Ratnayake
et al. [33] reported similar results for the lipid content of
Guatemalan coffee extracts, such as 57 mg per cup of
25 ml espresso, 50 mg per cup (150 ml) for metal screened
coffee extract (French Press) and 1.9 mg per cup (150 ml)
for drip-filtered coffee.
Caffeine DE, DL, SL and Bo showed a similar content
of caffeine per cup of coffee. SE, KK and F contained a
little less, NE had a notably smaller amount of caffeine per
cup of coffee, and Bia again brought up the rear at
21.6 mg/cup.
Fig. 6 Content per cup of
coffee brew (30 ml for DE, SE,
NE, Bia, and 120 ml for DL,
SL, Bo, KK, F) prepared
according to the different
extraction methods (DE, SE,
NE, Bia, DL, SL, Bo, KK and F)
of (a) total solids in grams (TS/
g), (b) fatty acids in grams (fatty
acids/g), amount of 0.1 M
NaOH for titration to (c) pH 6.6
and (d) pH 8, respectively, in
milliliters per cup (ml 0.1 M
NaOH), (e) caffeine in
milligrams (caffeine/mg),
(f) 3-O-caffeoyl quinic acid in
milligrams (3-CQA/mg) and
(g) 5-O-caffeoyl quinic acid in
milligrams (5-CQA/mg). The
error bars correspond to the
standard deviation of the mean
(s95 %)
616 Eur Food Res Technol (2013) 236:607–627
123
Bell et al. [55] studied the influence of extraction time,
volume, grinding and ratio of ground coffee to water on the
content of caffeine as well as on the content of total solids
for filter coffee and boiled coffee, and reported values
comparable to those found in this study. Bunker and
McWilliams [56] reported a higher content of caffeine for
brews prepared in a dripolator and made with a percolator.
However, they did not specify either the coffee they used
or their ratio of coffee to water.
The importance of the choice of coffee as well as the
way of preparing the coffee brew including the coffee/
water ratio on the amount of caffeine and chlorogenic acids
per cup of coffee is highlighted by the recent study of
Crozier et al. [43,57]. Analyzing 20 espressi bought in
local coffee shops, the amount of caffeine per serving
ranged from 51 mg up to 322 mg, corresponding to caf-
feine concentrations of 1.6–6.5 mg/ml.
Chlorogenic acids The lunghi contained more chloro-
genic acids per cup of coffee than the espressi. This was
more pronounced in the case of 5-CQA, as it is less water
soluble and therefore better extracted when washed out
with a higher amount of hot water. In their study on
espressi served in local coffee shops, Crozier et al. [43,57]
also measured the content of chlorogenic acids per cup of
espresso and found ranges of 5–97 mg per serving for
3-CQA and 12–215 mg per serving for the 5-CQA,
consistent with the values found in this study.
In general, the content per cup of coffee (30 ml for
espressi, 120 ml for lunghi) was highest in a lungo, fol-
lowed by the espressi, and lowest for the mocha extraction.
The amount of the analyzed components per cup of coffee
brew seemed to be influenced mainly by a combination of
extraction temperature and pressure as well as the amount
of water used for extraction. The higher the water to coffee
ratio, the more was washed out in the cup: the content per
cup was higher for the lunghi than for the espressi. The
higher the extraction pressure, the more was extracted: the
lunghi prepared on the fully and semi-automatic coffee
machines had a higher content per cup than the Bayreuth
coffee machine extraction and the filter coffee. The tem-
perature, however, was also important: the French Press
extraction had similar contents per cup as the lunghi from
the fully and semi-automatic coffee machines, although the
extraction times were different (4 min in contrast to 35 s).
The small amount of components per cup of mocha could
be explained by the fact that the mocha extraction is gen-
erally regarded as espresso while having a water to coffee
ratio like a lungo. If one would have taken a cup of 120 ml
of mocha, the content per cup of coffee would have to be
multiplied by a factor of four, leading to the highest content
per cup of coffee among all extraction types studied here.
This was most probably due to the high extraction tem-
perature in the percolator.
The strong influence of the water to coffee ratio on the
content per cup of coffee was also shown by Crozier et al.
[43,44], analyzing the content of caffeine and chlorogenic
acids of 20 different espressi from local coffee shops.
Alves et al. [49,52,53], studying the influence of the
brewing time and procedure (espresso, mocha, filter coffee,
press-pot, boiled and Turkish coffee) on the amount of
several constituents like tocopherols or isoflavones in
coffee brew, highlighted also the big influence of the water
to coffee ratio as well as the extraction temperature and
pressure on the content of components in the cup of coffee.
Extraction efficiency
In the preceding sections, the focus was on the coffee itself
(a sip or a full cup) as presented to the consumer. We now
turn to extraction efficiency, describing the quantity in
grams of a given component in the cup per gram of roast and
ground coffee (R&G) that has been extracted. This serves to
inform on the technical (and eventually economic) aspects
of the extraction mode. The results are given in Fig. 7and in
the Electronic Supplementary Material (Supp. Table 4). In
most cases, the lungo extractions were more efficient than
the espressi extractions, due to the higher amount of water
washing out the ground coffee. This effect was even more
pronounced for compounds that are less water soluble,
especially the 5-CQA.
The NE extraction efficiency was found to have a rel-
atively higher standard deviation, probably due to vari-
ability in the amount of ground coffee per capsule. For all
other extracts, the amount of coffee was controlled and
hence showed little variability. Among all the different
types of extraction investigated, Bia extraction was often
the most efficient. This goes in line with studies by Perez-
Martı
´nez et al. [36] on the influence of the type of
extraction on the antioxidant capacity of coffee brew,
where they found the highest extraction efficiency of
antioxidants in the mocha extraction. This may have been
due to the higher extraction temperature in comparison
with the other extraction methods. As early as 1958,
Merritt and Proctor, among others, reported that a higher
extraction temperature led to higher extraction efficiency of
soluble solids, caffeine and chlorogenic acids [58].
Total solids The amount of total solids washed out per
gram of ground coffee corresponds to the extraction yield.
The maximum extraction yield was given by Bia extraction
(31.2 %), followed by Bo (26 %). Interestingly, even filter
coffee showed a relatively high extraction yield of 19 % in
comparison with the other brewing types. Merritt and
Proctor [58] reported an extraction yield of 13.8–20.4 % on
dry basis at an extraction temperature of 93 C and an
extraction time of 0.5 min to 10 min for gauze filtered
coffee.
Eur Food Res Technol (2013) 236:607–627 617
123
Titratable acidity DE and SE extract had significantly
fewer extracted acids per gram of ground coffee than all the
other brewing types, the latter showing no significant dif-
ferences (except Bia). Titration to pH 8 revealed one
exception, that is the Bia brewing method, which had a
relatively higher extraction efficiency for acids in the range
from pH 6.6 to 8.0.
The higher extraction efficiency for acids found in a
lungo relative to an espresso may be explained by the
following: (i) the larger amount of water in a lungo resulted
in a higher degree of extraction or (ii) the darker roast used
for espresso led to a stronger degradation and loss of acids
in the roasted coffee beans. Considering that the Bia
extract, which was prepared from a dark roasted coffee and
a ratio of water to coffee similar to a lungo, showed a high
amount of extracted acids, the first explanation may be
more plausible here.
Headspace intensity Bia showed a clear maximum
headspace intensity. The filter methods, surprisingly, also
yielded high extraction efficiency for volatile compounds
per gram of R&G. These brewing methods were therefore
able to produce an intense coffee aroma from a relatively
small amount of ground coffee. As expected, the intensity
of the aroma above the coffee (per gram of R&G) was
much higher for an espresso than for a lungo, as shown in
Fig. 4.
Fig. 7 Content per gram of
ground coffee (R&G) prepared
according to the different
extraction methods (DE, SE,
NE, Bia, DL, SL, Bo, KK and F)
of (a) total solids in weight
percent (TS/w. %), (b) fatty
acids in weight percent (fatty
acids/w. %), amount of 0.1 M
NaOH in milliliters (ml 0.1 M
NaOH) for titration to (c)pH
6.6 and (d) pH 8, respectively,
(e) caffeine in weight percent
(caffeine/w. %), (f) total
headspace intensity in area
counts per gram (intensity/
counts), (g) 3-O-caffeoyl quinic
acid in weight percent (3-CQA/
w. %) and (h) 5-O-caffeoyl
quinic acid in weight percent
(5-CQA/w. %). The error bars
correspond to the standard
deviation of the mean (s95 %)
618 Eur Food Res Technol (2013) 236:607–627
123
Content of fatty acids The most efficient extraction of
fatty acids was performed with French Press extraction.
Brewing with a paper filter resulted in coffee with the
lowest fatty acid content, which is consistent with the
findings of Peters [5].
Caffeine and chlorogenic acids The extraction effi-
ciency of caffeine was comparable to that of total solids,
with the exception of filter coffee. The latter showed a
relatively higher efficiency for caffeine than for total solids
(extraction yield), most probably because the solids are
retained in the paper filter, whereas caffeine is not. The
extraction efficiency of 3-CQA was similar to that of caf-
feine in the case of the lunghi. Bia showed a much lower
extraction efficiency of 3-CQA in comparison with caf-
feine. The espresso brewing methods were found to extract
the 3-CQA much less efficiently than the lunghi brewing
methods. In the case of 5-CQA, this was even more pro-
nounced. Our values for the extraction efficiency of caf-
feine, 3-CQA and 5-CQA are consistent with values in the
literature [35,58]. Ludwig et al. [37] compared filter coffee
with espresso extraction and Perez-Martı
´nez et al. [36]
compared espresso extraction with mocha, filter and
plunger coffee extraction regarding the extraction effi-
ciency of antioxidants. Both confirm a higher extraction
efficiency of antioxidants for filter coffee and mocha
extraction, respectively, than for espresso.
The differences in the extraction efficiencies of caffeine,
3-CQA and 5-CQA can be explained either by the water
solubility of the respective quantities, decreasing from
caffeine (20 g/L at 20 C[59]) to 3-CQA (soluble in hot
water [60]) to 5-CQA (personal experience of the authors)
or by a decreased amount of chlorogenic acids in the
espresso powder itself, due to the darker roast degree. Bia
extraction showed a higher degree of extraction than the
lunghi for all compounds analyzed, except for the chloro-
genic acids. The darker roast degree for the espressi could
account for this difference. French Press extraction showed
the most efficient extraction of 3-CQA and 5-CQA, due to
the long extraction time with relatively hot water. This is
consistent with the findings of Merritt and Proctor, who
found a higher extraction efficiency for caffeine and
chlorogenic acids with prolonged extraction time and
higher extraction temperature [58]. The results presented
here are also consistent with Zanoni et al. [61], who found
a higher content of total solids and caffeine with prolonged
extraction time.
Regarding the extraction efficiency, the mocha extraction
was the most efficient brewing method, followed by the
lunghi and the espressi. The most influencing parameters
seemed to be the extraction temperature and time. Within
the infusion methods, the French Press extraction had the
highest extraction efficiency (high extraction time and
temperature), followed by the Bayreuth coffee machine
extraction and the filter coffee (high extraction time, low
pressure), whereas the lunghi of the fully and semi-auto-
matic coffee machines (short extraction time, high pressure)
showed the smallest extraction efficiency. Lo
´pez-Galilea
et al. [3], Ludwig et al. [37] and Perez-Martı
´nez et al. [36]
reported higher extraction efficiencies, also, with prolonging
the contact time of the water with the coffee powder,
especially in the case of less water-soluble substances,
consistent with the findings of this study. The comparatively
low extraction efficiency for chlorogenic acids of the mocha
and the espressi extractions may be explained partly by their
low water solubility, but partly also by the darker roast
degree used for these extraction methods.
In general, concerning the extraction efficiencies, the
higher amount of water used for the preparation of a lungo
led to higher extraction efficiencies for the lunghi than for
the espressi. The values presented here differ somewhat to
the values of Peters [5]. This may be due to the difference
in coffee they used, to the roast or milling degree of the
coffee as well as to the different water to coffee ratio. To
clarify the influence of these factors, detailed experimental
studies would be needed. Ludwig et al. [37] compared the
temporal evolution of the extraction process between an
espresso and filter coffee and showed that more than 70 %
of the antioxidants are washed out in the first eight seconds
of an espresso extraction. For filter coffee, they reported an
U-shaped time–concentration profile of the extracted anti-
oxidants. The peak in extraction efficiency at the end of the
extraction process is explained by a longer contact time of
the water with the coffee powder caused by the water
pressure release at the end of the extraction process (there
is no more water lying above the coffee powder pulling
down due to gravity). Combining the results of this study
and of Ludwig et al. means that in an espresso, the com-
ponents were extracted quickly, but not very efficiently.
The preparation of a lungo under high pressure (fully and
semi-automatic coffee machine) extracted the components
quickly, also, but the higher amount of water led to a higher
extraction efficiency. In filter coffee, the extraction was
slower and most efficient in the beginning and at the end of
the extraction process, according to Ludwig et al. [37].
This extraction peak at the end of the brewing seemed to
compensate for the lack of pressure during the extraction,
because the study presented here shows similar extraction
efficiencies for lunghi prepared with (DL, SL) or without
(KK, F) high pressure.
The degree of grinding seemed to have a minor influ-
ence, here, in comparison with the water to coffee ratio: the
lunghi DL and SL, prepared with a coarser grind, had a
higher extraction efficiency than the corresponding espressi
DE and SE, prepared with a finer ground and smaller water
to coffee ratio. In general, of course, the extraction effi-
ciency increases with decreasing particle size, as was
Eur Food Res Technol (2013) 236:607–627 619
123
shown, for example, by Andueza et al. [62] and Spiro et al.
[63].
Sensory evaluation
The results of the consensus profiling of the different
coffee brewing methods are shown in Figs. 8,9and 10 and
reveal clear differences between the respective extraction
methods.
Concerning the crema, only DE, SE, DL, SL and NE were
evaluated, as the other types of extraction do not generate a
crema. NE had noticeably the highest amount of crema with
the most intensive color, whereas DE had the finest crema.
The texture/body of the respective brews was clearly
highest in the case of the espressi DE, SE and NE, and the
lowest for KK and F.
Aroma DE and SE not only had the highest overall
aroma intensity, but also the highest intensity of the roasty
aroma. The filter extractions KK and F were found to have
the least aroma intensity. KK extraction and SE extraction
exhibited a surprisingly high intensity of fruity aroma.
In the flavor profile, the KK extraction had a negligible
fruity note, but a high intensity of sweetness. Filter coffee
showed a relatively weak but very well-balanced flavor profile.
The flavor profile of Bo, SL and DL was also well balanced.
The differences in acidity between the extraction methods
were minor. In the case of the espressi, the roasty and bitter
attributes clearly dominated the flavor of the coffee brew.
Aftersensation The bitterness of the espressi remained in
the aftersensation and was perceivable in the lunghi DL
and SL as well as in Bo. KK and F showed a small but
well-balanced profile in the aftersensation. Acidity was
only a minor attribute in the aftersensation. The aftersen-
sation aroma decreased from DE, SE and NE to Bia, DL
and SL, to Bo and F, and finally to KK. Astringency
diminished in a similar way.
Advantages and shortcomings of the respective
extractions
Espressi
Sensory Aspects All the espressi extractions were charac-
terized by a strong roasty and bitter flavor, a pronounced
body and a prolonged aftersensation. The crema was the
parameter which differed most between the respective
Fig. 8 Sensory profiles of the respective extraction types (DE, SE, NE, Bia, DL, SL, Bo, KK, F) for Optic of crema (O-Quantity, O-Fineness,
O-Color) and Aroma (A-Overall Intensity, A-Fruity, A-Cereal/Nuts, A-Roasty)
620 Eur Food Res Technol (2013) 236:607–627
123
espresso extraction methods. Espresso from a semi-auto-
matic coffee machine showed a fine crema, darker than the
crema of an espresso made with the fully automatic coffee
machine. The single-serve capsule system was the extrac-
tion with the highest quantity of the darkest crema.
Analytical Aspects The espressi showed the highest
concentration of TS, the highest concentration of titratable
acids and the highest concentrations of caffeine, 3-CQA
and 5-CQA. The pH values of the different espressi were
similar.
Lunghi
Sensory Aspects In general, DL and SL showed a little less
intensity than the corresponding espressi, but still a higher
intensity than the other lungo extractions. The main dif-
ference between SL and DL was the crema, which was
finer, lighter and found in a higher quantity in the case of
SL. Hence, DE performed better than SE with respect to
crema, while the situation was reversed for the lunghi.
The infusion methods Bo, KK and F were characterized
by modest aromaticity, a relatively weak roasty and bitter
note, and a pronounced sweetness.
Analytical Aspects There were only minor differences
between the respective lunghi extractions regarding the
concentrations of total solids, titratable acids, caffeine,
3-CQA and 5-CQA, as well as in respect of the Brix value
and the headspace intensity. In most cases, filter coffee
brought up the rear with the lowest intensity of the
respective attributes.
Main characteristics of the extractions
DE highest fineness of crema, strong roasty note, highest
cereal/nuts score for aroma, highest bitterness in flavor
(together with SE), highest Brix value.
SE strong fruity note in aroma, distinct roasty note,
highest cereal/nuts score for flavor, highest acidity and
bitterness in aftersensation, highest bitterness in flavor
(together with DE).
NE darkest crema, highest amount of crema, strong
roasty note, highest body, lower pH value, negligible fatty
acid content (note: different type of coffee; not Antigua
Guatemala).
Bia no crema, middle-range sensory values, same fla-
vor profile as NE although they are based on a different
Fig. 9 Sensory profiles of the respective extraction types (DE, SE, NE, Bia, DL, SL, Bo, KK, F) for Flavor (F-Fruity, F-Cereal/Nuts, F-Roasty,
F-Sweetness, F-Acidity, F-Bitterness)
Eur Food Res Technol (2013) 236:607–627 621
123
coffee; positioned between espresso and lungo from an
analytical point of view; relatively high amount of fatty
acids.
DL, SL Both are characterized by a total solids content
of circa 1.3 % and a pH of 5.7, which is in the mid-region
of all extraction types studied here. The DL shows a
slightly higher titratable acidity and a higher content of
fatty acids than the SL. In sensory, they are characterized
by a balanced mid-score aroma and taste impression. In the
aftersensation, aroma and bitterness are pronounced. The
biggest differences between DL and SL were the optic and
quantity of crema.
Bo higher roasty note, higher aromaticity, stronger cer-
eal/nuts note, more body and more bitterness than the other
filter methods (KK and F); highest amount of fatty acids,
high pH value.
KK high intensity of fruity aroma, pronounced sweet-
ness in flavor, moderate aromaticity, relatively low roasty
note and bitterness; relatively low pH value.
Fwell-balanced profile, with low fruity note; negligible
content of fatty acids, low pH value.
Comparison of analytics with sensory
In analytics, absolute quantities or concentrations are
measured, in this study for a sip and a whole cup of coffee,
and per gram of R&G (extraction efficiency). In sensory
evaluation, the panelists tasted a sip of coffee. Hence, the
most appropriate analytical data to be correlated with
the sensory profiles were those for a sip of coffee, that is,
for 10 ml of coffee brew (corresponding to circa one sip of
coffee for an adult), as summarized in Fig. 4. The sensory
results are given in Figs. 8,9and 10. The following cor-
relations were observed with the respective correlation
coefficients (significance was approved by a one-sided F
test at the alpha =0.1 level): r
2
(total solids vs. texture/
body) =0.69, r
2
(headspace intensity vs. aroma overall
intensity) =0.73, r
2
(caffeine vs. AS-bitterness) =0.69,
r
2
(caffeine vs. AS-astringency) =0.75, r
2
(sum of 3-CQA
and 5-CQA vs. AS-bitterness) =0.68, r
2
(sum of 3-CQA
and 5-CQA vs. AS-astringency) =0.75; for the following
two correlations, we have observed smaller correlation
coefficients classified only as a trend of positive
Fig. 10 Sensory profiles of the respective extraction types (DE, SE, NE, Bia, DL, SL, Bo, KK, F) for Texture (T-Body) and Aftersensation (AS-
Aroma, AS-Acidity, AS-Bitterness, AS-Astringency)
622 Eur Food Res Technol (2013) 236:607–627
123
correlation: r
2
(caffeine vs. F-bitterness) =0.58, r
2
(sum of
3-CQA and 5-CQA vs. F-bitterness) =0.51.
Content of total solids versus texture/body
The higher the content of TS, the higher the body was rated
by the panelists. The high scores for body of NE in com-
parison with its content of TS were striking. This may have
been due to the influence of the huge amount of crema.
Headspace intensity versus aroma intensity
The higher the sensory overall intensity in aroma, the
higher is the total headspace intensity in the HS SPME
GC/MS measurements.
pH value, titratable acidity versus acidity in flavor
and aftersensation
In this study, no correlation between pH or titratable
acidity and perceived acidity in flavor or aftersensation was
found. Bia extraction is worthy of note, as it achieved the
highest score for flavor acidity while being the least acidic
coffee brew (highest pH value).
Furthermore, the pH value of the brew and the titratable
acidity did not correlate with one another. It should be
borne in mind that many acids which exist in a coffee brew
are not (fully) deprotonated at the pH of the brew, and thus
do not contribute to the brew’s pH value, but are measured
during titration with a base.
The lack of correlation between these attributes may be
explained by the small differences in acidity of the dif-
ferent extraction types in the sensory evaluation. Interac-
tions with other sensory attributes may be superimposed at
this point. For example, perceived bitterness is affected by
changes in the pH of a beverage (see, e.g., Reference
[64,65]). However, the question of whether high bitterness
masks the acidity of a brew cannot be answered at this
point. In addition, the temperature of the servings may have
an influence on the perception of acidity. In general, acidity
is more pronounced at lower temperatures of the coffee
brew. As the Bo extraction has the same intensity in flavor
acidity as the KK and filter coffee extracts while having a
higher temperature, the influence of the temperature of the
extract seems to be minor.
The correlation of the pH value and/or the titratable
acidity with the sensory perceived acidity has been widely
studied. Andueza et al. [54] did not find a correlation of the
pH value with sensory perceived acidity, either. In contrast
to this study, Fuse et al. [66] found a correlation between
the pH value of the brew, the roast degree, the titratable
acidity and the sourness intensity of the brew studying the
acidity of Guatemala filter coffee by flow injection analysis
with electrochemical detection. The range of titratable
acidity, however, was much larger than in this study
(15–30 ml 0.1 M NaOH to pH 8.2 per 50 ml of coffee
brew, Fuse et al., versus 3–12 ml 0.1 M NaOH to pH 8 per
50 ml of coffee brew, this study).
Clifford [67] stated in 1988 that ‘‘in effect, the reaction
of the acid with the receptor is a titration, and thus very
similar to the process used in measuring titratable acidity.’’
He cited studies of Voilley et al. (1981) and Harvey (1920)
who found no correlation between the pH value and the
perceived acidity, but mentioned that the perceived acidity
also depends on the reserve acidity due to undissociated
acids.
Maier et al. [12,64,6873] performed an extensive
study on the acids in coffee, ranging from the composition
of the acids in coffee to the correlation of the analytically
measured acidity with the sensory attribute acidity. The
sensory evaluation was performed on cold coffee extracts
(40 C) diluted with water and showed a linear correlation
between the titratable acidity to pH 6 and the acidic taste of
different coffee extractions, but no correlation with the pH
value of the brews. In their studies, they identified 67 % of
the acids contributing to the titratable acidity as well as the
sensory acidity of the coffee extract, with acetic and citric
acid being the most important ones.
Rodrigues et al. [42] analyzed the organic acids with
UV/HPLC of several Arabica and Robusta coffees as well
as the sensory acidity. Concerning the Robusta coffees,
they found a good correlation between the total amount of
organic acids and the sensory acidity, but no correlation in
the case of the Arabica brews. Lugaz et al. [74] performed
an extensive study on the perception of acid taste in general
as a function of saliva flow rates, pH and chemical com-
position of the acid and concluded that the titratable acidity
rather than the pH should contribute to the acid taste.
According to Sivetz et al. [75], who studied the influ-
ence of acidity on coffee flavor in 1972, none of our coffee
brews falls into the acceptable range of palatability, lying
between pH 4.95 and pH 5.15 for an Arabica coffee.
Interestingly, none of the panelists were complaining about
the palatability of the respective coffee brews. This may be
due to a shift in consumer’s preferences in the last 40 years
to coffees with a less pronounced acid taste.
Caffeine, chlorogenic acids versus bitterness, astringency
There was a tendency toward higher sensory scores for
bitterness and astringency in flavor and aftersensation with
increasing amounts of caffeine. This was even more pro-
nounced with increasing amounts of chlorogenic acids.
One exception is again Bia extraction: The bitterness in
the sensory results scored much higher than would have
been assumed with respect to the concentration of caffeine
Eur Food Res Technol (2013) 236:607–627 623
123
and chlorogenic acids. The relatively high bitterness of Bia
is most probably due to other compounds in the coffee
brew.
The studies of Andueza et al. [54] on the influence of the
ratio of ground coffee to water in espresso extraction also
showed no significant correlation between increasing
content of caffeine and chlorogenic acids with increasing
bitterness and astringency. Frank et al. [76,77]and
Kreppenhofer et al. [78] have recently identified a range of
substances responsible, among others, for bitterness in cof-
fee brews. Taste dilution analysis showed that compounds
like caffeoyl-quinides, di-caffeoyl-quinides, feruloyl-qui-
nides (‘‘pleasant bitterness of coffee’), 4-vinylcatechol
oligomers (‘‘harsh and espresso-like bitterness’), as well as
(furan-2-yl) methylated benzene diols and triols (‘‘astringent
mouth feel and clear bitter taste’’) contributed significantly
to the bitterness of a coffee brew. Caffeoyl-quinides,
di-caffeoyl-quinides, feruloyl-quinides and (furan-2-yl)
methylated benzene diols and triols also contributed to the
astringency of the coffee brew [76,78]. The chlorogenic
acids 3-CQA and 5-CQA, however, produced no bitter taste.
The correlation found in our study between the chlorogenic
acids and the perceived bitterness in taste can therefore not
be ascribed to the concentration of 3-CQA and 5-CQA.
Most probably, the concentration of substances responsible
for the bitter taste has a similar dependence on the extraction
method as 3-CQA and 5-CQA. Blumberg et al. [48]showed
that the more polar the bitter-tasting compound, the faster
it is extracted with hot water, monocaffeoyl quinides
(‘‘pleasant bitterness of coffee’’), for example, being already
extracted to about one-third of their total content in the first
10 ml of coffee.
Sweetness and optic of crema
The sensory attributes sweetness and optic of crema do not
have any analytical pendant in this study. In principle, the
crema may influence sensory evaluation by altering the
distribution of coffee in the mouth, leading to either an
increase in intensity of the sensory attributes like roasty or
a masking of attributes like bitterness [1,79]. In addition,
the crema may act as ‘an aroma-sealing lid’’ [ 1], retaining
the lower volatile organic compounds in the coffee whereas
enhancing the high volatile organic compounds in the
headspace [53]. In fact, we observed a three-step ranking in
intensity of the sensory attributes in the sensory evaluation:
(i) high scores for the espressi (with crema), (ii) middle-
range scores for the lunghi with crema and (iii) lower
scores for the lunghi without crema. However, in the
analytical measurements of the concentrations of the
respective quantities, we observed, roughly speaking, a
high intensity for the espressi and a low intensity for the
lunghi. This was also reflected in a principal component
analysis (PCA) of the sensory and analytical data (Fig. 11).
In the sensory data, the same three groups can clearly be
identified, from odor intense coffees with strong bitterness
and body (with crema) to less intense coffees (lunghi from
automatic and semi-automatic coffee machines, with
crema, and Bia) to sweet- and low-bodied coffees (lunghi
without crema). This three-level ranking in the sensory data
is not reflected in the instrumental results, which have been
classified into two categories, espressi and lunghi, as shown
in Fig. 11b. In other words, the clear differentiation
between lunghi with or without crema in the sensory
evaluation was not reflected in the instrumental data. As
the sensory evaluation was performed by a trained panel,
visual influence by the crema is unlikely, suggesting that
the sensory interaction, that is, the density of the crema in
the mouth, is more important.
Conclusions
Nine of the most common extraction methods of preparing
a cup of coffee were characterized: espresso and lungo with
a semi-automatic coffee machine, espresso and lungo with
a fully automatic coffee machine, espresso from a single-
serve capsule system, mocha made with a percolator and
Fig. 11 Biplot from the
principal component analysis of
(a) the sensory data (PC1 vs.
PC2, 78 % of total variance)
and (b) the chemical data (PC1
vs. PC2, 96 % of total variance)
624 Eur Food Res Technol (2013) 236:607–627
123
lunghi prepared with a French Press, a Bayreuth coffee
maker and filter coffee.
The technical differences in these extraction methods
led to differences in the quantity of the analytical aspects
studied, exhibited different extraction efficiencies and, last
but not least, extracted coffees with different sensory
profiles. In general, the espressi showed a higher concen-
tration of the respective quantities than the lunghi. How-
ever, when the contents per cup were compared, the lunghi
generally had a higher content than the espressi. Hence, the
overall uptake of coffee components is higher when
drinking a lungo, although the consumer does not neces-
sarily notice this as the concentration, and therefore the
sensory experience, is lower in a lungo.
The extraction efficiency of the respective compounds
was mainly driven by their solubility in water, a higher
amount of water, as in the extraction of a lungo, generally
leading to higher extraction efficiency. A prolonged
extraction time and/or a higher extraction temperature
further enhanced extraction efficiency.
Comparing the analytical aspects with the sensory eval-
uation, the following positive correlations were revealed
total solids—texture/body
headspace intensity—aroma intensity
concentrations of caffeine/chlorogenic acids—bitter-
ness and astringency.
There was neither a correlation of the pH value nor of
the titratable acidity with the sensory aspect of acidity.
In conclusion, this study describes the analytical and
sensory properties of nine different types of coffee
extraction, based on Guatemalan coffee. It was not the aim
of the study to establish the best means of coffee extrac-
tion, as this is driven mainly by the personal preferences of
the consumers, who will set their own standards for a good
cup of coffee.
Conflict of interest The authors declare that they have no conflict
of interest.
Open Access This article is distributed under the terms of the
Creative Commons Attribution License which permits any use, dis-
tribution, and reproduction in any medium, provided the original
author(s) and the source are credited.
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... As for the titratable acidity of light coffee, a difference (p ≤ 0.05) was found during storage, in contrast to medium and dark coffee, where no difference (p > 0.05) was detected, either between raw and processed CBC or between processed CBC through 141 days of storage. Gloess et al. [39] state that the titratable acidity impacts the sensory quality of the drink. The values herein at t 0 (0.031 to 0.039%) were greater than those reported by Bellumori et al. [12], who utilize beans roasted at 200 • C/12 min (light-medium roast) and obtained values that varied from 0.025 to 0.028% chlorogenic acid. ...
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