Content uploaded by Kassaye Tolessa Sherge
Author content
All content in this area was uploaded by Kassaye Tolessa Sherge on Mar 19, 2018
Content may be subject to copyright.
Content uploaded by Kassaye Tolessa Sherge
Author content
All content in this area was uploaded by Kassaye Tolessa Sherge on Mar 19, 2018
Content may be subject to copyright.
Research Article
Received: 14 July 2016 Revised: 11 October 2016 Accepted article published: 27 October 2016 Published online in Wiley Online Library:
(wileyonlinelibrary.com) DOI 10.1002/jsfa.8114
Influence of growing altitude, shade and
harvest period on quality and biochemical
composition of Ethiopian specialty coffee
Kassaye Tolessa,a,c* Jolien D’heer,cLuc Duchateauband Pascal Boeckxc
Abstract
BACKGROUND: Coffee quality is a key characteristic for the international market, comprising cup quality and chemical bean
constituents. In Ethiopia, using total specialty cup scores, coffees are grouped into Q1 (specialty 1) ≥85 and Q2 (80–84.75). This
classification results in market segmentation and higher prices. Although different studies have evaluated the effects of altitude
and shade on bean quality, optimum shade levels along different altitudinal ranges are not clearly indicated. Information on
effects of harvest periods on coffee quality is also scanty. The present study examined the influences of these factors and their
interactions on Ethiopian coffee quality
RESULTS: Coffee from high altitude with open or medium shade and early to middle harvest periods had a superior bean quality.
These growing conditions also favoured the production of beans with lower caffeine. An increasing altitude, from mid to high, at
approximately 400 m, decreased caffeine content by 10%. At high altitude, dense shade decreased Q1 coffee by 50%. Compared
to late harvesting, early harvesting increased the percentage from 27% to 73%. At mid altitude, >80% is Q2 coffee.
CONCLUSIONS: Changes of quality scores driven by altitude, shade and harvest period are small, although they may induce dra-
matic switches in the fraction Q1 versus Q2 coffee. The latter affects both farmers’ profits and competitiveness in international
markets.
© 2016 Society of Chemical Industry
Keywords: Arabica coffee; altitude; shade; cup quality; caffeine; chlorogenic acid
INTRODUCTION
Coffee is the world’s most traded commodity after oil1and
its quality is a key characteristic for the international coffee
market.2,3Coffee quality is determined by organoleptic char-
acteristics (cup quality), physical appearance and chemical
constituents.4,5The increase in demand and consumption of
high-quality, single-origin, specialty coffee with specific charac-
teristics results in market segmentation (e.g. a specialty coffee
market) and creates a strong potential and new opportunities for
coffee-producing countries.6–8Market segmentation for specialty
coffee attracts new customers and results in higher coffee prices.9
For example, specialty coffee beans receive a premium price that
is approximately 20– 50% higher compared to regular coffee
beans.10
Ethiopia is one of the top ten coffee-producing countries in the
world and the largest exporter in Africa.10 The country is naturally
gifted with a suitable climate and has the potential to produce
single origin specialty Arabica coffee beans with a wide range of
flavors.11,12 Recently, nine single origin specialty coffees (Jimma,
Nekemte, Illubabor, Limu, Tepi, Bebeka, Yirga Chefe, Sidamo and
Harar) were identified and entered into trade circuits of the world
coffee market. Among them, the sundried coffee beans from
‘Harar’, the so-called ‘Mocca’ and the washed beans from ‘Yirga
Chefe’ are considered to be the finest and best quality coffee.13
Currently, specialty coffee accounts for approximately 20% of
Ethiopia’s coffee export and there is also a very high potential to
boostitsshareintheworldmarket.
14 Thus, an improved specialty
coffee market is considered to be beneficial for Ethiopia to remain
competitive in the international market. Ethiopian producers will
benefit from high-quality coffee if its supply remains stable 6and, if
the global coffee chain is not changing as a result of deregulation,
new consumption patterns and/or evolving corporate strategies
(e.g. branding).15 Producers, on the other hand, should implement
improved, sustainable agronomic practices (e.g. shade-grown cof-
fee) to produce beans desired by consumers.
Along the coffee supply chain, however, numerous factors affect-
ing coffee quality have been identified. Genetic traits,16 grow-
ing environment17–20 and posthar vest processing methods5,21 are
known to predominantly affect coffee quality. The most important
∗Correspondence to: K Tolessa, College of Agriculture and Veteri-
nary Medicine, Jimma University, PO Box 307, Jimma, Ethiopia.
E-mail: kasech_tolassa@yahoo.com
aCollege of Agriculture and Veterinary Medicine, Jimma University, PO Box 307,
Jimma, Ethiopia
bDepartment of Comparative Physiology and Biometrics, Faculty of Veterinary
Medicine, Ghent University, Belgium, Salisburylaan 133, 9820 Merelbeke,
Belgium
cIsotope Bioscience Laboratory – ISOFYS, Ghent University, Gent, Belgium,
Coupure Links 653, 9000 Gent, Belgium
J Sci Food Agric (2016) www.soci.org © 2016 Society of Chemical Industry
www.soci.org K Tolessa et al.
environmental factor, most commonly linked to influence coffee
quality, is the altitude where coffee is grown.17,19 Some studies
have reported that the best quality of Arabica coffee comes from
a higher altitude as a result of lower daily temperatures, which
results in a slower ripening of the beans and allows more time for
bean filling.
Shade is also found to favour a sustainable production of
high coffee quality, especially under suboptimal conditions where
temperatures are higher than optimal.19,20 Some studies have
indicated that shade reduces temperature stress in the canopy
and lengthens the maturation period of coffee berries. It also
reduces periodic over-bearing and a subsequent die back of coffee
plants.22 In line with this, Läderach et al.7reported that coffee qual-
ity scores increase with the level of shading. Bosselmann et al.,23
on the other hand, reported that, at high altitude, shade had no
significant effect on cup quality attributes. At lower altitude, how-
ever, shade reduced the number of small beans with no significant
effect on coffee sensorial attributes. In a study by Lara-Estrada and
Vaast,2shade was reported not to have any significant influenceon
coffee organoleptic properties under any of the conditions of alti-
tude and fertilization. These contradicting reports show that opti-
mum shade management practices are highly site specific and also
that further studies are required to clearly indicate its influence on
coffee quality attributes across different altitudinal gradients.
In Ethiopia, coffee trees are grown under shade of different lev-
els and shade management is among the dominant agronomic
practices in traditional organic coffee growing systems.22,24 Recent
studies show that shade significantly affects yield25 and cup qual-
ity attributes of Ethiopian coffee.24,26 Although different studies
have been carried out to evaluate the effect of shade on coffee
yield and quality, optimum shade levels along different environ-
mental gradients have not yet been investigated in the country.
In addition, no study has been carried out aiming to investigate
how altitude and shade interactively affect cup quality and the bio-
chemical composition of Ethiopian coffee beans.
In addition to shade and growing altitude, coffee harvesting peri-
ods were also reported to affect coffee quality. Guyot et al.27 indi-
cated that late harvested coffee beans had better beverage quality
and larger bean size than early harvested beans. Bertrand et al.,28
on the other hand, reported that early harvested coffee beans were
better with respect to beverage quality than late harvested beans.
In another study, early harvesting was found to improve coffee
quality compared to late harvesting.7This also highlights the need
for further research aiming to clearly determine the effects of har-
vest periods on coffee bean quality.
To the best of our knowledge, no studies exist that analyse the
interactive effects of growing altitude, shade levels and harvest
periods on Ethiopian coffee bean quality. Hence, the main objec-
tive of the present study was to examine their interactive effects
on physical characteristics, cup quality attributes and selected bio-
chemical compounds.
MATERIALS AND METHODS
Study site
The study was carried out from October 2013 to February 2014
in the Mana district, Jimma zone, Oromia regional state, south
western Ethiopia. Mana is known as one of the predominant Coffea
arabica L. growing areas. It is located at altitudinal ranges between
1470 and 2610 m a.s.l., at 8∘67’N and 37∘07’E. The district has a
total area of 47 898ha of which 23% is at low (<1550 m a.s.l.), 65%
is at mid (1550–1750 m a.s.l.) and the remaining 12% is at high
altitude (>1750 m a.s.l.).29 Annual average temperature and rainfall
are 20.5 ∘C and 1523 mm, respectively. The soil type in the study
area is uniform and described as Nitosol, with a pH ranging from
4.5 to 5.5.30
Treatments and experimental design
Two altitudinal ranges were selected: high (1950– 2100 m a.s.l.)
and mid altitude (1600–1680 m a.s.l.) with an average tempera-
ture over 30 years of 19.3 ±1.9 ∘C and 22.5 ±2.6 ∘C, respectively.
Different shade levels of ten coffee farms (five from each altitudi-
nal range) with comparable coffee ages (7– 10 years) were selected
taking care that agronomic management practices did not differ
substantially among the farms. Shade levels above canopies of
the coffee trees in each farm were quantified using the Sunscan
canopy analysis system (Type SS1, BF5-RPDA1; Delta-T Devices,
Cambridge, UK) and grouped into three levels: open (no shade),
medium (40–55%) and dense shade (65– 85%). During measure-
ments, the reference sensor was placed in open sun (no shade) and
the shade percentage was determined in relation to this reference
point. In the harvest season, from October 2013 to February 2014,
red ripe cherries from each altitude and shade level were harvested
at three different periods (early, middle and late). Early and middle
harvesting at mid altitude of open and medium shades were car-
ried out from the first to the third week of October 2013, whereas
late harvested beans were collected from the first to the third week
of November 2013. Coffee samples at high altitude with open to
medium shade levels were harvested early (first week of Decem-
ber 2013), middle (end of December 2013) and late (third week of
January 2014). Under dense shade, on the other hand, early har-
vest was carried out in the fourth week of December 2013, middle
harvest in the third week of January 2014 and late harvest in the
first week of February 2014).
The experiment was arranged in a split– split plot design with
two levels of altitude (mid and high) as a main plot, three levels
of shade (open, medium and dense) as a subplot and three levels
of harvest periods (early, middle and late) as sub-subplot with five
replications (farms) at each attitude.
Coffee quality analysis
Coffee cherries were sundried immediately after harvest on raised
beds in accordance with standard agronomic practices until a
moisture content of approximately 11.5%. The dried coffee cher-
ries were then dehusked using a coffee hulling machine (Coffee
Huller; McKinnon, Aberdeen, UK) at Jimma University College of
Agriculture and Veterinary Medicine and stored at room tempera-
ture packed in hermetic plastic bags. The 100-bean weight (g) of
the dried beans was determined in three replicates using a digi-
tal sensitive balance (CTG-6H+; Citizen, Piscataway, NJ USA) and
the bean diameter (mm) was measured on 45 randomly selected
beans per treatment, using a digital calliper (IP 67, CD-20-PPX;
Mitutoyo Technology, Kawasaki, Japan).
For quality analysis, 350 g of each coffee sample was sent to
the Ethiopia Commodity Exchange (ECX), Jimma Branch, for phys-
ical and cup quality analysis, out of which 100 g was roasted
at 160 –200 ∘C for 8–12 min using a roasting machine (4 Bar-
rel Roaster; Probat, Emmerich am Rhein, Germany) adjusted to
medium roasting.31 The roasted beans were tipped out into a cool-
ing tray and rapidly cooled by blowing cold air through the beans
for 4 min and then ground with a coffee grinding machine (K32SB2;
Mahlkonig, Hamburg, Germany). Next, 13.75 g of ground coffee
was diluted in 250 mL of hot water (93 ∘C) to prepare an infusion.
wileyonlinelibrary.com/jsfa © 2016 Society of Chemical Industry J Sci Food Agric (2016)
Quality and biochemical composition of Ethiopian specialty coffee www.soci.org
Five cups of brewed coffee of each coffee sample were prepared
for analysis and a team of three professional cuppers, who operate
in ECX, tasted and gave a score for each of the five cups.
The preliminary total quality score comprises physical (40/100)
and preliminary cup quality (60/100) scores. The criteria commonly
used to evaluate the physical quality of coffee beans include the
presence of defects: primary (e.g. full black and sour beans) and
secondary (e.g. partial black, insect damaged and broken beans)
defects and odour.32 Cup quality was evaluated based on acidity,
body, flavour and cup cleanness scores. The sum of these four
cup quality attributes gives preliminary cup quality with a score
between 0 and 60. Hence, the sum of both physical and preliminary
cup quality ranges between 0 and 100 and is used to classify the
samples into different grades (grade 1 =91– 100; grade 2 =81– 90;
grade 3 =71 –80; and grade 4 =63 –70). If the scores of all samples
were higher than 70, cup quality for specialty coffees (coffees
with grades ranging from 1 to 3) was further assessed based on
overall cup preference, acidity, body, aroma, flavour, aftertaste,
uniformity, cup cleanness, sweetness and balance, each on a scale
ranging from 0 to 10. Based on the total specialty scores, coffee
samples were further grouped into specialty 1 (Q1) ≥85, specialty
2 (Q2) (80– 84.75) and a regular commercial coffee (<80).31 The
grading was carried out in accordance with an old ECX guideline.
However, recently, ECX established a new grading system that
reduced the old ten preliminary total quality levels to five levels:
grade 1 ≥85; grade 2 =75 – 84; grade 3 =63– 74; grade 4 =47–62;
and grade 5 =31–46.33 Coffee samples that fall in grade 1 and 2
qualify for specialty coffee and are further grouped into specialty
1(Q1)≥85 and specialty 2 (Q2) (80– 84.75). The preliminary total
quality assessment scores for grade 2 should be higher than 80 to
be qualified as specialty 1 (Q1).
Caffeine and chlorogenic acid extraction
Green coffee beans were ground (<0.5mm) prior to extraction
using a grinder (M20; IKA, Staufen, Germany). The extraction
was performed using 100 mg of ground coffee beans with 10 mL
of methanol:water:acetic acid (30:67.5:2.5; v/v/v) containing
2mgmL
−1ascorbic acid, as described by Alonso-Salces et al.34 The
extract was placed in an ultrasonic bath for 15 min and filtered
over a 0.45-μm polytetrafluoroethylene filter prior to injection into
a liquid chromatography system.
Liquid chromatography analysis
Using an established liquid chromatography-time of flight-mass
spectrometry method,35 four subclasses of chlorogenic acids were
identify in the green coffee samples: caffeoylquinic acid, feru-
loylquinic acid, dicaffeoylquinic acid and feruloyl-caffeoylquinic
acid. Quantification was performed using liquid chromatog-
raphy equipped with a photodiode array detector (Surveyor;
Thermo Finnigan, San Jose, CA, USA) at 280 nm for caffeine
and 320 nm for chlorogenic acids. The chromatographic sepa-
ration was performed using a prevail C18 (250 ×4.6 mm, 5 μm;
Alltech, Klerken-Houthulst, Belgium) column, maintained at
25 ∘C. The chromatographic method was based on Alonso-Salces
et al.34 using a combination of 0.2% acetic acid in water (v/v)
and high-performance liquid chromatography grade methanol.
The injection volume was 50 𝜇Lataflowrateof1mLmin
−1.
Calibration was achieved by injecting a concentration series of
caffeine and chlorogenic acid every 30 samples, using an adapted
response factor for the other chlorogenic acid types. The total
chlorogenic acid concentration is reported as the sum of all above
individual chlorogenic acids. Data acquisition and processing
were performed using ChromQuest, version 4.1 SP2 (Thermo
Fisher Scientific, Waltham, MA, USA).
Moisture content determination
Toexpress the data on a dr y weight basis insteadof on a wet matter
basis, the moisture content of the coffee samples was determined
in accordance with AOAC procedures.36
Statistical analysis
Data were analysed with SAS, version 9.2 (SAS Institute Inc., Cary,
NC USA) using the mixed model procedure for a split–split plot
design with altitude as the main plot, shade as subplot and harvest
period as sub-subplot. Significant differences between treatment
means were separated using Tukey’s honestly significant differ-
ence (HSD) test.
RESULTS
Coffee quality
Significant interactions between altitude and shade were
observed for total specialty coffee cup quality and its specific
specialty cup quality attributes (overall cup preference, acidity,
body, flavour and aftertaste) (P<0.01) (Table 1). Quality scores
for total specialty cup quality (86.5), overall cup preference (8.2),
acidity (8.3), body (8.2), flavour (8.0) and aftertaste (8.0) were
higher for coffee beans grown at high altitude combined with
open or medium shade level. The interaction between altitude
and harvest period significantly influenced physical quality, over-
all cup preferences and acidity of coffee beans (Table2). Coffee
beans grown at mid altitude and collected during late harvest
period had the lowest physical quality score (34.0), whereas scores
for overall cup preferences and acidity were higher for coffee
beans grown at high altitude and harvested in early or middle
harvest periods (Table 2). Har vest period by shade interactions
were not significant for any of the above variables. There were also
no three-way interactions between altitude, shade and harvest
period on any of the coffee bean quality attributes.
Altitude as a main effect (Table 3) indicated that preliminary cup
quality, preliminary total quality, total specialty cup quality and
aroma were lower at mid altitude. The scores for each of these
quality attributes increased with increasing altitude (Table 3). Cof-
fee beans grown in dense shade had a higher physical quality
score (36.7). Coffee grown at open or medium shade gave a higher
total specialty cup score (84.5) and overall cup preference (7.9).
Beans harvested at early and middle harvest period were generally
higher in preliminary cup quality, preliminary total quality, total
specialty cup quality, overall cup preference and body scores com-
pared to late har vested beans ( Table 3).
100-bean weight, caffeine and total chlorogenic acid content
Three-way interactions between altitude, shade and harvest peri-
ods were significant for caffeine content (Table4). Highest caf-
feine content (17.9 g kg−1) was obtained from mid altitude with
dense shade and early harvested beans, whereas the lowest con-
tent (14.5 g kg−1) was from high altitude with medium shade and
middle harvested beans (Table 4). No three-way interactions were
found either for 100-bean weight or for total chlorogenic acids
contents of coffee beans.
J Sci Food Agric (2016) © 2016 Society of Chemical Industry wileyonlinelibrary.com/jsfa
www.soci.org K Tolessa et al.
Tab le 1. Interactive effect of altitude (A): high (1950– 2100 m a.s.l.), mid (1600– 1680 m a.s.l.) and shade (S): open (0%), medium
(40–55%) and dense (65– 85%) on physical quality (PQ), preliminary cup quality (PCQ), preliminary total quality (PTQ), total specialty
cup quality (TSCQ) and specific specialty cup quality scores
Specific specialty cup quality attributes
A S PQ PCQ PTQ TSCQ OCP Acidity Body Aroma Flavour AT
High Open 35.6 ±0.4 a 49.6 ±0.8 a 85.2 ±0.8 a 86.5 ±0.9 a 8.2±0.2 a 8.3 ±0.1 a 8.2 ±0.2 a 8.1 ±0.2 ab 8.0 ±0.2 a 8.0 ±0.2 a
Medium 36.6 ±0.4 a 49.6 ±0.7 a 86.2 ±0.8 a 86.5 ±0.8 a 8.3 ±0.1 a 8.3±0.1 a 8.1 ±0.1 ab 8.2 ±0.1 a 7.9 ±0.1 a 8.0 ±0.2 a
Dense 36.8 ±0.6 a 47.6 ±0.8 a 84.4 ±0.8 a 83.7 ±0.7 b 7.6 ±0.1 b 7.9 ±0.2 b 7.7 ±0.1 bc 7.7 ±0.1 bc 7.6 ±0.1 b 7.5 ±0.1 b
Mid Open 35.4 ±0.4 a 45.6 ±0.4 a 81.0 ±0.7 a 82.6 ±0.3 b 7.6 ±0.1 b 7.6 ±0.1 bc 7.6 ±0.1 c 7.5 ±<0.1 c 7.5 ±0.1 b 7.4 ±0.1 b
Medium 36.2 ±0.4 a 46.6 ±0.4 a 82.8 ±0.6 a 83.2 ±0.3 b 7.6 ±0.1 b 7.8 ±<0.1 bc 7.7 ±0.1 bc 7.6 ±0.1 c 7.5 ±0.1 b 7.5 ±<0.1 b
Dense 36.6 ±0.5 a 45.6 ±0.4 a 82.2 ±0.7 a 83.4 ±0.2 b 7.6 ±<0.1 b 7.8 ±0.1 ab 7.7 ±0.1 bc 7.6 ±0.1 bc 7.6 ±<0.1 b 7.5 ±0.1 b
P-value 0.96 0.22 0.29 0.006 <0.0001 0.006 0.008 0.023 0.007 0.0025
OCP, overall cup preference; AT, aftertaste. Different lowercase letters in the same column indicate a significant difference according to Tukey’sHSD post-hoc test (P<0.01).
Results are shown as the mean ±SE. The bolded values are the significant value i.e., P-values are <0.01.
Table 2. Interactive effect of altitude (A): high (1950– 2100m a.s.l.), mid (1600–1680 m a.s.l.) and harvest periods (HP): early, middle and late on the
physical quality (PQ), preliminary cup quality (PCQ), preliminary total quality (PTQ), total specialty cup quality (TSCQ) and specific specialty coffee cup
quality scores
Specific specialty cup quality attributes
A HP PQ PCQ PTQ TSCQ OCP Acidity Body Aroma Flavour AT
High Early 36.8 ±0.5 a 49.8 ±0.7 a 85.6 ±0.8 a 86.9 ±0.8 a 8.3 ±0.2 a 8.5 ±0.1 a 8.3 ±0.1 a 8.1 ±0.1 a 8.1 ±0.2 a 8.1 ±0.2 a
Middle 36.6 ±0.6 a 49.2 ±0.6 a 85.8 ±0.6 a 85.4 ±0.8 a 8.1 ±0.2 a 8.2 ±0.1 ab 7.9 ±0.1 a 8.0 ±0.2 a 7.8 ±0.1 bc 7.8 ±0.1 a
Late 34.0 ±0.4 b 47.8 ±0.9 a 84.4 ±0.9 a 84.3 ±0.8 a 7.7 ±0.1 b 7.9 ±0.1 b 7.8 ±0.1 a 7.9 ±0.1 a 7.7 ±0.1 bc 7.8 ±0.2 a
Mid Early 36.6 ±0.5 a 46.8 ±0.4 a 83.4 ±0.7 a 83.1 ±0.3 a 7.6 ±0.1 b 7.7 ±0.1 b 7.6 ±0.1 a 7.6 ±<0.1 a 7.5 ±0.1 c 7.5 ±0.1 a
Middle 36.6 ±0.2 a 46.4 ±0.4 a 83.2 ±0.4 a 83.3 ±0.4 a 7.7 ±0.2 b 7.8 ±0.1 b 7.7 ±0.1 a 7.5 ±0.1 a 7.5 ±0.1 c 7.4 ±0.1 a
Late 34.0 ±0.4 b 44.6 ±0.3 a 79.4 ±0.4 a 82.7 ±0.2 a 7.6 ±0.1 b 7.7 ±<0.1 b 7.5 ±<0.1 a 7.5 ±<0.1 a 7.5 ±<0.1 c 7.5 ±0.1 a
P-value 0.004 0.93 0.067 0.29 0.007 0.0008 0.09 0.86 0.012 0.35
OCP, overall cup preference; AT, aftertaste. Different lowercase letters in the same column indicate a significant difference according to Tukey’s HSD
post-hoc test (P<0.01).
Results are shown as the mean ±SE. The bolded values are the significant value i.e., P-values are <0.01.
Altitudes by shade interactions were significant for total chloro-
genic acid content (P<0.01) but not for 100-bean weight and caf-
feine contents. Total chlorogenic acid contents decreased from
mid to high altitude and from dense to open shading at high alti-
tude (Table 5). Coffee beans from mid altitude and open sun had a
higher total chlorogenic acid content (46.5 g kg−1), whereas beans
from high altitude and open shading gave 40.5 g kg−1.Theinter-
actions between altitude and harvest period were not significant
for any of the 100-bean weight, caffeine or total chlorogenic acid
content. The interactions between shade and harvest periods had
a significant effect on 100-bean weight but not on caffeine and
total chlorogenic acid content (Table 6). Coffee beans produced in
dense or medium shade gave higher bean weights at any harvest
period.
The main effects are given in Table 7. Altitude affected both
the caffeine content and 100-bean weight. Coffee beans pro-
duced at mid altitude had a higher caffeine content (17.2 g kg−1)
than beans produced at high altitude (15.5 g kg−1), whereas
the bean weight was 16.9 and 14.1 g at high and mid alti-
tude, respectively. Beans grown at medium or dense shade
were approximately 10% heavier than beans in open sun.
By contrast, the harvest period as main factor had no effect
on 100-bean weight, caffeine and total chlorogenic acid
content.
DISCUSSION
Several studies have reported influences of altitude17,27 and
shade19,26,37,38 on coffee bean quality. The present study, however,
expanded the scope and clarified the interaction of altitude, shade
and harvest periods on physical quality, preliminary cup quality,
preliminary total quality, total specialty cup quality and its specific
cup quality attributes (acidity, body, aroma), 100-bean weight
and the biochemical composition (caffeine and chlorogenic acid
content) of Ethiopian coffee beans. Caffeine and chlorogenic
acid are considered to have a direct impact on human health. In
addition, these two chemicals are key biochemical components
of coffee beans with respect to determining its beverage quality.
The present study further discussed the effects of altitude, shade
and harvest periods on both components.
Total specialty cup quality and its specific quality attributes (e.g.
overall cup preference, acidity and flavour) increased with both
altitude and shade level. At high altitude, however, dense shade
decreased green bean cup quality and the percentage of specialty
1 (Q1) beans by approximately 50% (Table8). Coffee beans grown
in cooler environments accumulate sufficient sugars and lipids.37,39
Both are key compounds with respect to determining coffee as
a beverage and are positively correlated with bean quality.2,20
Dense shade, however, further decreased air temperature around
the coffee fruits. This effect in combination with the effect of
altitude on temperature could reduce growing temperature to a
wileyonlinelibrary.com/jsfa © 2016 Society of Chemical Industry J Sci Food Agric (2016)
Quality and biochemical composition of Ethiopian specialty coffee www.soci.org
Table 3. Physical quality (PQ), preliminary cup quality (PCQ), preliminary total quality (PTQ), total specialty cup quality (TSCQ) and specific specialty
cup quality scores of coffee beans as affected by altitude (A): high (1950– 2100 m a.s.l.), mid (1600–1680 m a.s.l.), shade (S): open (0%), medium
(40– 55%) and dense (65– 85%) and harvest periods (HP): early, middle and late
Specific specialty cup quality attributes
Factor PQ PCQ PTQ TSCQ OCP Acidity Body Aroma Flavour AT
A High 36.3 ±0.3a48.9 ±0.5a85.2 ±0.5a85.5 ±0.5a8.0 ±0.1a8.2 ±0.1a7.9 ±0.1a7.9 ±0.1a7.9 ±0.1a7.9 ±0.1a
Mid 36.1 ±0.3a45.9 ±0.3b82.6 ±0.4b83.0 ±0.2b7.6 ±<0.1b7.7 ±0.1b7.6 ±<0.1b7.5 ±<0.1b7.5 ±<0.1b7.5 ±0.1b
P-value 0.57 <0.0016 <0.0025 <0.004 <0.024 <0.012 0.011 <0.008 0.03 0.016
S Open 35.5 ±0.3b47.6 ±0.6ab 83.3 ±0.7a84.5 ±0.6ab 7.9 ±0.1a7.9 ±0.1a7.9 ±0.1a7.8 ±0.1a7.7 ±0.1a7.7 ±0.1ab
Medium 36.4 ±0.3ab 48.1 ±0.5a84.5 ±0.6a85.7 ±0.5a7.9 ±0.1a8.0 ±0.1a7.9 ±0.1a7.8 ±0.1a7.7 ±0.1a7.8 ±0.1a
Dense 36.7 ±0.4a46.6 ±0.5b83.1 ±0.6a83.6 ±0.4b7.6 ±0.1b7.9 ±0.1a7.7 ±0.1a7.7 ±0.1a7.6 ±0.1a7.5 ±0.1b
P-value 0.008 0.033 0.06 0.009 0.0003 0.37 0.055 0.148 0.17 0.04
HP Early 36.2 ±0.4ab 48.3 ±0.5a84.5 ±0.6a84.9 ±0.6a7.9 ±0.1a8.1 ±0.1a7.9 ±0.1a7.8 ±0.1a7.8 ±0.1a7.8 ±0.1a
Middle 36.7 ±0.3a47.8 ±0.5a84.5 ±0.4a84.4 ±0.5a7. 9 ±0.1a7.9 ±0.1ab 7.8 ±0.1ab 7.8 ±0.1a7.7 ±0.1ab 7.6 ±0.1a
Late 35.7 ±0.3b46.2 ±0.6b81.9 ±0.7b83.5 ±0.4b7.6 ±0.1b7.8 ±0.1b7.8 ±0.1b7.7 ±0.1a7.6 ±0.1b7.6 ±0.1a
P-value 0.06 0.004 0.0009 0.003 0.006 0.005 0.027 0.37 0.04 0.32
OCP, overall cup preference; AT, aftertaste. Different lowercase letters in the same column indicate a significant difference according to Tukey’s HSD
post-hoc test (P<0.01).
Results are shown as the mean ±SE. The bolded values are the significant value i.e., P-values are <0.01.
Table 4. Interactive effect of altitude (A): high (1950– 2100 m a.s.l.),
mid (1600– 1680 m a.s.l.), shade (S): open (0%), medium (40– 55%) and
dense (65– 85%) and harvest periods (HP): early, middle and late on
caffeine content
Altitude Shade Harvest period Caffeine (g kg−1)
High Open Early 15.9 ±0.2 de
Middle 15.1 ±0.3 ef
Late 15.1 ±0.4 ef
Medium Early 17.1 ±0.2 abc
Middle 14.5 ±0.3 f
late 15.1 ±0.5 ef
Dense Early 15.0 ±0.3 ef
Middle 16.4 ±0.4 cd
Late 15.2 ±0.3 fe
Mid Open Early 16.7 ±0.3 bcd
Middle 17.2 ±0.3 abc
Late 16.4 ±0.3 cd
Medium Early 17.1 ±0.5 abc
Middle 17.8 ±0.4 a
Late 16.9 ±0.3 a –d
Dense Early 17.9 ±0.1 a
Middle 17.7 ±0.5 b
Late 17.1 ±0.4 abc
P-value 0.0002
Different lowercase letters in the same column indicate a significant
difference according to Tukey’s HSD post-hoc test
(P<0.01). Results are shown as the mean ±SE; expressed as g kg−1
on a dry weight basis. The bolded values are the significant value i.e.,
P-values are <0.01.
level below optimum (i.e. 18 ∘C),40 resulting in reducedcoffee bean
quality. In areas where air temperature is relatively cooler, such
as at high altitudes, shade levels higher than 40– 50% are hence
not beneficial because growing temperature may decrease below
optimum.
The ideal growing temperature of Arabica coffee ranges
between 18 and 21 ∘C,41 and values above or below this
Table 5. Interactive effect of altitude (A): high (1950– 2100 m a.s.l.),
mid (1600– 1680 ma.s.l.) and shade (S): open (0%), medium (40– 55%)
and dense (65– 85%) on 100-bean weight, caffeine and total chloro-
genic acid content
AS
100-bean
weight (g)
Caffeine
(g kg−1)
Total chlorogenic
acid (g kg−1)
High Open 16.1 ±0.3 a 15.4 ±0.2 a 40.5 ±0.9 c
Medium 17.5 ±0.3 a 15.6 ±0.4 a 42.7 ±0.8 bc
Dense 17.0 ±0.2 a 15.6 ±0.2 a 43.2 ±0.7 bc
Mid Open 13.3 ±0.2 a 16.8 ±0.2 a 46.5 ±0.8 a
Medium 14.2 ±0.2 a 17.3 ±0.2 a 43.7 ±0.86 b
Dense 14.7 ±0.2 a 17.6 ±0.2 a 45.4 ±1.0 ab
P-value 0.16 0.34 0.0046
Different lowercase letters in the same column indicate a significant
difference according to Tukey’s HSD post-hoc test
(P<0.01). Results are shown as the mean ±SE; expressed as g kg−1on
a dry weight for caffeine and total chlorogenic acid. The bolded values
are the significant value i.e., P-values are <0.01.
optimum level predispose coffee beans to incomplete matu-
ration and poor quality. Bosselmann et al.23 also reported that, at
high altitudes, lower temperatures as a result of excess shade from
trees resulted in reduced coffee bean quality. By contrast, at mid
to low altitude, higher temperature induces the accumulation of
chemical compounds such as butan-1,3-diol and butan-2,3-diol in
coffee beans, which reduces quality attributes (aroma, acidity).42
At high altitude, differences between open and medium shade
levels on coffee bean quality were not significant. This result was in
agreement with previous findings reported by Guyot et al. 27 and
Bosselmann et al.23 This indicates that the temperature around
coffee trees grown under both shade levels was still within the
optimum range for coffee growth23 or allows better exposure of
the trees to sunlight. At mid altitude, on the other hand, shade was
observed not to have any significant effect on coffee bean quality.
This might be related to leaf fall from the shade tree during the dry
season, indicating that farmers should consider the best adaptable
shade tree type to grow coffee under consistent shade level.
J Sci Food Agric (2016) © 2016 Society of Chemical Industry wileyonlinelibrary.com/jsfa
www.soci.org K Tolessa et al.
Table6. Interactiveeffect of shade (S): open (0%), medium (40 – 55%)
and dense (65– 85%) and harvest periods (HP): early, middle and late
on 100-bean weight, caffeine and total chlorogenic acid content
SHP
100-bean
weight (g)
Caffeine
(g kg−1)
Total chlorogenic
acid (g kg−1)
Open Early 13.7 ±0.3 bc 16.3 ±0.2 d 44.9 ±1.2 a
Middle 15.2 ±0.3 b 16.2 ±0.4 cd 43.1 ±1.5 a
Late 15.2 ±0.6 b 15.7 ±0.3 bcd 42.4 ±1.4 a
Medium Early 15.9 ±0.5 a 17.2 ±0.3 a 44.3 ±1.0 a
Middle 15.8 ±0.5 a 16.1 ±0.6 d 42.3 ±0.9 a
Late 15.8 ±0.5 a 15.9 ±0.4 cd 42.9 ±0.8 a
Dense Early 15.8 ±0.4 a 16.5 ±0.5 abc 45.5 ±1.2 a
Middle 15.8 ±0.5 a 17.0 ±0.4 ab 42.1 ±1.1 a
Late 15.9 ±0.5 a 16.1 ±0.4 cd 45.1 ±0.7 a
P-value 0.009 0.049 0.35
Different lowercase letters in the same column indicate a significant
difference according to Tukey’s HSD post-hoc test
(P<0.01). Results are shown as the mean ±SE; expressed as g kg−1on
a dry weight for caffeine and total chlorogenic acid. The bolded values
are the significant value i.e., P-values are <0.01.
Table 7. 100-bean weight, caffeine and total chlorogenic acid
as affected by altitude (A): high (1950– 2100 m a.s.l.) and mid
(1600– 1680 m a.s.l.), shade (S): open (0%), medium (40 –55%) and
dense (65– 85%) and harvest periods (HP): early, middle and late
Factor Leve l
100-bean
weight (g)
Caffeine
(g kg−1)
Total chlorogenic
acid (g kg −1)
A High 16.9 ±0.2 a 15.5 ±0.2 b 42.1 ±0.5 b
Mid 14.1 ±0.2 b 17.2 ±0.1 a 45.2 ±0.5 a
P-value 0.0009 <0.0001 0.012
S Open 14.7 ±0.3 b 16.1 ±0.2 a 43.5 ±0.8 a
Medium 15.9 ±0.3 a 16.4 ±0.3 a 43.2 ±0.6 a
Dense 15.9 ±0.3 a 16.6 ±0.3 a 44.3 ±0.7 a
P-value <0.0001 0.059 0.311
HP Early 15.2 ±0.3 a 16.7 ±0.2 a 44.9 ±0.7 a
Middle 15.6 ±0.3 a 16.5 ±0.3 ab 42.5 ±0.8 b
Late 15.6 ±0.4 a 15.9 ±0.2 b 43.5 ±0.6 ab
P-value 0.27 0.015 0.039
Different lowercase letters in the same column indicate a significant
difference according to Tukey’s HSD post-hoc test
(P<0.01). Results are shown as the mean ±SE; expressed as g kg−1on
a dry weight for caffeine and total chlorogenic acid. The bolded values
are the significant value i.e., P-values are <0.01.
At present, air temperature is also increasing as a result of global
climate change. Besides reducing coffee bean quality, this increase
in air temperature is reducing the area suitable for Arabica coffee
production.43,44 Growing coffee trees at higher altitude or under
tailored shading conditions could be implemented as a possible
approach to adapt to the effects of climate change and to sustain
the production of high quality coffee beans. However, in our study
area, the high altitude area is limited. Hence, shading adaptation
has to be considered in view of climate change.
Beans harvested at early and mid harvest period were generally
higher in preliminary cup quality, preliminary total quality, total
specialty cup quality, overall cup preference and body scores
compared to late harvested beans. For example, at high altitude
Table 8. Percentage of coffee samples that are ranked as specialty 1
(Q1) and specialty 2 (Q2) grown at different altitude (high and mid),
shade levels (open, medium and dense)aand harvest period (early,
middle and late)b
Percentage of specialty coffee
Altitude
Specialty
1(Q1)
Specialty 2
(Q2)
High Shade level Open 53.346.7
Medium 66.733.3
Dense 33.366.7
Mid Shade level Open 6.793.3
Medium 13.386.7
Dense 6.793.3
High Harvest period Early 73.027.0
Middle 53.047.0
Late 27.073.0
Mid Harvest period Early 7.093.0
Middle 20.080.0
Late 7.093.0
aEach value is averaged across different harvest period (early, middle
and late). bEach value is averaged across different shade levels (open,
medium and dense).
(Table 8), early harvesting led to 73% of specialty 1 (Q1) coffee
beans compared to 27% for late harvest. Better bean quality as a
result of early harvest was also reported in other studies.28,45 This
is possibly a result of the depletion of photo-assimilates because
of competition among fruits, which finally leads to a shortage
of photo-assimilates for the late developing fruits.37 In addition,
the production of coffee quality precursor compounds, which
accumulate in coffee beans, is markedly high during endosperm
expansion and dry matter accumulation stages.46 At a later stage
of bean development, however, most of these quality precursors
are remobilized towards lignin biosynthesis and drop in relative
content.47 At mid altitude, the harvest period did not significantly
influence coffee bean quality. This is probably a result of temper-
ature at mid altitude being higher (approximately 4 ∘C) compared
to temperature at high altitude. High temperature accelerates
bean ripening and automatically results in shorter time intervals
between the different harvest periods.
Coffee bean weight increased with increasing altitude. The result
is in agreement with previous studies.37 Coffee beans grown
at higher altitudes mature slowly and are generally harvested
1–2 months later than beans from mid altitudes. A slower matu-
ration of coffee beans allows better bean filling (e.g. more lipid
accumulation).2,19 It is also reported that environmental factors
and agricultural managements modify the physiology of coffee
fruit development and ripening.48 Among environmental factors,
temperature plays a significant role in regulating bean maturation
and ripening processes.27 The results of the present study support
the notion that low temperature slows down the ripening pro-
cess (resulting in a delayed harvesting period by approximately 50
days on average) and allows better bean filling, resulting in heavier
beans.37
Shading also promotes bean weight. Coffee beans grown under
medium or dense shade are heavier than beans grown in open
sun. Beans grown under shaded conditions mature slower because
shading also lowers the temperature around the coffee fruits and,
in general, the beans are harvested 2–4 weeks later than beans
wileyonlinelibrary.com/jsfa © 2016 Society of Chemical Industry J Sci Food Agric (2016)
Quality and biochemical composition of Ethiopian specialty coffee www.soci.org
in open sun,23,37 In addition, shade has also been reported to
reduce the number of floral initiations per plant and allow more
assimilate partitioning to each developing bean.23 Partitioning of
more assimilates to individual beans increases coffee bean weight.
Caffeine contents of our coffee samples ranged from 14.5 to
17.9 g kg−1(Table 4). The results are in agreement with previous
studies by Silvarolla et al.,49 Ky et al.50 and Bekele.51 However, these
values varied by interaction effects of altitude, shade and harvest
periods. Early harvested beans from mid altitude grown under
dense shade contained the highest amount of caffeine, whereas
the lowest caffeine content was found at high altitude, medium
shading and middle harvest. In coffee bean development, biosyn-
thesis and accumulation of most chemicals, including caffeine, is
markedly higher at the early development stage and is reduced at
a later stage of ripening.46 At the later stage of bean development,
the compounds are also remobilized towards lignin biosynthesis
and their contents are relatively decreased compared to contents
at early bean development stages.46,47 The results of the present
study corroborate these findings and indicate that early harvested
beans contain more caffeine than late harvested ones.
The present study also demonstrated the influence of altitude
on caffeine content. An increase in altitude by 400 m decreased the
caffeine content by 10% (Table 7). Sridevi and Parvatam52 reported
similar findings, whereas Avelino et al.17 and Bertrand et al.53 on
the other hand, reported the opposite. Bertrand et al.53 showed
that an increase in altitude by 500 m increased caffeine content by
15%. In the study by Bertrand et al.,53 however, plots from very low
altitude (e.g. 700 to 1600 m a.s.l.) were also included. This might
explain such discrepancies.
Chlorogenic acids are the main phenolic compounds in coffee
beans, ranging from 6% to 12% on a dry weight basis.54 In the
present study, total chlorogenic acid content (sum of four sub-
classes) varied from 40.5 to 45.2 g kg−1on a dry weight basis
(Table 5). These values are generally lower than values previously
reported for coffee,55,56 but much higher than values reported by
Ky et al.50 and Bekele.51 In addition, we found that the values were
affected by variation in altitude and shade. Total chlorogenic acid
content decreased from mid to high altitude and from dense to
open shading at high altitude. At mid altitude, however, coffee
beans from mid altitude and open sun accumulated more chloro-
genic acid.
Growing temperature has a direct influence on production and
accumulation of chlorogenic acids.39 The higher temperature at
mid altitude probably resulted in higher chlorogenic acid produc-
tion and accumulation in coffee beans grown at mid than at high
altitude. A higher chlorogenic acid content indicates that coffee
beans are relatively immature.55 These differences in chlorogenic
acid contents and bean maturation resulted in coffee bean qual-
ity differences (more Q1 coffees at high than at mid altitude). The
result was in agreement with results reported by Avelino et al.56
and Link et al.55 However, studies by Bertrand et al.,53 reported the
opposite. In the present study, the altitude ranged from 1600 to
2010 m a.s.l. In the study by Bertrand et al.53 plots from very low
altitude (e.g. 700 to 1600 m a.s.l.) were also included. This might
explain such discrepancies.
The present study generally indicates that coffee growing at
high altitude, in open or medium shade, and harvested at an
early or middle period, shows enhanced potential for producing
specialty 1 (Q1) coffee (Table 8). These growing conditions also
favour the production of coffee beans with lower caffeine and
chlorogenic acid contents. Coffee beans with lower caffeine but
higher chlorogenic acid contents are appreciated and preferred in
many consumer countries because of their positive health effect.
Chlorogenic acid acts as antioxidant and has radical scavenging
properties. It makes coffee an acceptable beverage. It also has
anti-pathogenic and allelophatic properties54 and is described as
being important for disease resistance in coffee beans.57
Coffee beans grown at mid altitude had lower bean quality com-
pared to high altitude, and were grouped mostly as Q2 specialty
coffees. This indicates that there is scope for mid altitude farmers,
which occupy most of the area, to produce more Q1 coffee beans.
For example, growing trees under medium-shaded conditions and
selectively harvesting the beans at mid harvest could potentially
increase the percentage of Q1 coffees (Table8).
CONCLUSIONS
Overall, the results of the present study show that growing cof-
fee at high altitude with open or medium shade, as well as an
early or middle harvest period, increased the potential of produc-
ing beans with superior quality. In general, small changes of qual-
ity attributes, driven by altitude, shading and harvest periods, can
cause substantial switches in Q1 versus Q2 classification. This qual-
ity segmentation affects coffee bean price and farmers’ competi-
tiveness in international markets. The present study, however, did
not investigate year-by-year variations and soil type effects. Future
studies are needed to integrate these impacts.
ACKNOWLEDGEMENTS
We gratefully thank NUFFIC, Netherlands Organization for Inter-
national Cooperation in Higher Education (NICHE), for financial
support. We also acknowledge the Ethiopia Commodity Exchange
(ECX) for their support in evaluating coffee cup quality, the Goma
1 coffee plantation enterprise for allowing us to use the coffee pro-
cessing facilities, and the farmers of the Mana district for working
on their coffee farms.
REFERENCES
1 Pendergrast M, Coffee: second to oil? TCTJ 181:38 (2009).
2 Lara-Estrada L and Vaast P, Effects of altitude, shade, yield and fertil-
ization on coffee quality (Coffea arabica L. var. Caturra) produced in
agroforestry systems of the Northern Central Zones of Nicaragua,
in Second International Symposium on Multi-Strata Agroforestry Sys-
tems with Perennial Crops: Making Ecosystem Services Count for Farm-
ers, Consumers and the Environment,Turrialba,CostaRica,pp.17–21
(2007).
3 Jeszka-Skowron M, Zgoła-Grze´
skowiak A and Grze´
skowiakT,Analytical
methods applied for the characterization and the determination
of bioactive compounds in coffee. Eur Food Res Technol 240:19 – 31
(2015).
4 Agwanda C, Baradat P, Eskes A, Cilas C and Charrier A, Selection for
bean and liquor qualities within related hybrids of Arabica coffee in
multilocal field trials. Euphytica 131:1–14 (2003).
5 Joët LA, Descroix F, Doulbeau S, Bertrand B and Dussert S, Influence of
environmental factors, wet processing and their interactions on the
biochemical composition of green Arabica coffee beans. Food Chem
118:693– 701 (2010).
6 Oberthür T, Läderach P, Jurgen PHA and Cock JH, eds, Specialty Coffee:
Managing Quality. Internation Plant Nutrition Institute, Southeast
Asia Program, Penang, Malaysia (2012).
7 Läderach P, Oberthür T, Cook S, Iza ME, Pohlan JA, Fisher M et al.,Sys-
tematic agronomic farm management for improved coffee quality.
Field Crops Res 120:321–329 (2011).
8 Wood L, Research and Markets:Coffee Market in Brazil 2015 –2019 – High
Demand for Arabica Coffee, USA. Technavio, Elmhurst, USA (2015).
9 Labouisse JP, B Bellachew, Kotecha S and Bertrand B, Current Sta-
tus of Coffee (Coffea arabica L.)Genetic Resources in Ethiopia:
J Sci Food Agric (2016) © 2016 Society of Chemical Industry wileyonlinelibrary.com/jsfa
www.soci.org K Tolessa et al.
Implications for Conservation. Genetic Resources and Crop Evolu-
tion 55:1079– 1093 (2008).
10 Bart M, Seneshaw T, Tadesse K and Yaw N, Structure and perfor-
mance of Ethiopia’s coffee export sector. ESSP II Working Paper 66.
Washington, DC and Addis Ababa, Ethiopia: International Food Pol-
icy Research Institute (IFPRI) and Ethiopian Development Research
Institute (EDRI) (2014).
11 ICCO, Middle Africa briefing note, soft commodities: coffee,in Ecobank.
The Pan African Bank, Edward George, London (2014).
12 Coste R, Cambrony H and Tindall H, Coffee: The Plant and the Product.
Macmillan, London (1992).
13 MFA,The 4th World Coffee Conference in Addis Ababa, Ministry of Foreign
Affairs of Ethiopia, Addis Ababa, Ethiopia (2016).
14 Robert S, Frontlines: Foreign Aid Impact in US and Abroad, in Frontlines.
USID, Washington, DC, USA, p. 17 (2015).
15 Ponte S, The ‘latte revolution’? Regulation, markets and consumption
in the global coffee chain. World Dev 30:1099 –1122 (2002).
16 Leroy T, Ribeyre F, Bertrand B, Charmetant P, Dufour M, Montagnon
Cet al., Genetics of coffee quality. Braz J Plant Physiol 18:229–242
(2006).
17 Avelino J, Barboza B, Araya JC, Fonseca C, Davrieux F, Guyot B et al.,
Effects of slope exposure, altitude and yield on coffee quality in two
altitude terroirs of Costa Rica, Orosi and Santa María de Dota. JSci
Food Agric 85:1869– 1876 (2005).
18 Decazy F, Avelino J, Guyot B, Perriot JJ, Pineda C and Cilas C, Quality
of different Honduran coffees in relation to several environments.
J Food Sci 68:2356–2361 (2003).
19 Muschler RG, Shade improves coffee quality in a sub-optimal
coffee-zone of Costa Rica. Agrofor Syst 51:131 –139 (2001).
20 Vaast, Kanten Rv, Siles P, Dzib B, Franck N, Harmand J and Genard
M, Shade: a key factor for coffee sustainability and quality, in ASIC
2004 20th International Conference on Coffee Science,Bangalore, India,
11– 15 October 2004, Association Scientifique Internationale du
Café (ASIC), Bangalore, India, pp. 887– 896 (2005).
21 Selmar D, Bytof G, Knopp SE and Breitenstein B, Germination of coffee
seeds and its significance for coffee quality. Plant Biol 8:260 –264
(2006).
22 Alemu MM, Effect of tree shade on coffee crop production. JSustDev
8:66 (2015).
23 Bosselmann A, Dons K, Oberthur T, Olsen CS, Ræbild A and Usma H,
The influence of shade trees on coffee quality in small holder coffee
agroforestry systems in Southern Colombia. Agric Ecosyst Environ
129:253– 260 (2009).
24 Yadessa A, Burkhardt J, Denich M, Woldemariam T, Bekele E and
Goldbach H, Effect of different indigenous shade trees on the
quality of wild arabica coffee in the Afromontane rainforests of
Ethiopia, in 22nd International Conference on Coffee Science, ASIC
2008. Campinas, SP, Brazil, 14 – 19 September 2008. Association
Scientifique Internationale du Café (ASIC), Campinas, Brazil, pp.
1227– 1233 (2009).
25 Kufa T, Yilma A, Shimber T, Netsere A and Taye E, Yield performance
of Coffea arabica cultivars under different shade trees at Jimma
Research Center, Southwest Ethiopia, in Proceedings of the Second
International Symposium on Multi-strata Agroforestry Systems with
Perennial Crops, Turrialba, Costa Rica, Turrialba, Costa Rica (2007).
26 Bote AD and Struik PC, Effects of shade on growth, production and
quality of coffee (Coffea arabica) in Ethiopia. J Hortic For 3:336 –341
(2011).
27 Guyot B, Gueule D, Manez J, Perriot J, Giron J and Villain L, Influence de
l’altitude et de l’ombrage sur la qualité des cafés arabica. Plant Rech
Dév 3:272– 280 (1996).
28 Bertrand B, Etienne H, Guyot B and Vaast P, Year of production and
canopy region influence bean characteristics and beverage quality
of Arabica coffee, in ASIC 2004 20th International Conference on
Coffee Science, Bangalore, India, 11 – 15 October 2004. Association
Scientifique Internationale du Café (ASIC), Paris, France, pp.878 – 886
(2005).
29 JARC, Recommended Production Technologies for Coffee and Associated.
Ethiopian Institute of Agricultural Research (EIAR), Addis Ababa,
Ethiopia (1996).
30 ARDO, Annual Report of Agriculture and Rural Development Office of
Manna Woreda, Yebbu, Manna. ARDO, Addis Ababa, Ethiopia (2008).
31 John AK, ECX Quality Operation Manual., Ethiopia Commodity
Exchange (ECX), Addis Ababa, Ethiopia (2011).
32 Santos JR, Sarraguça MC, Rangel AOSS and Lopes JA, Evaluation of
green coffee beans quality using near infrared spectroscopy: A
quantitative approach. Food Chem 135:1828– 1835 (2012).
33 Lemma B, ECX Adopts Five Level Coffee Quality Grading System.Ethiopia
Commodity Exchange (ECX), Addis Ababa, Ethiopia (2015).
34 Alonso-Salces , Rosa M, Serra F, Reniero F and Héberger K, Botanical
and geographical characterization of green coffee (Coffea arabica
and Coffea canephora): chemometric evaluation of phenolic and
methylxanthine contents. J Agric Food Chem 57:4224– 4235 (2009).
35 Alonso-Salces , Maria R, Guillou C and Berrueta LA, Liquid chromatog-
raphy coupled with ultraviolet absorbance detection, electrospray
ionization, collision induced dissociation and tandem mass spec-
trometry on a triple quadrupole for the on line characterization of
polyphenols and methylxanthines in green coffee beans. RapidCom-
mun Mass Spectrom 23:363 –383 (2009).
36 AOAC, Official Methods of Analysis of the Association of Official A nalytical
Chemists, 17th edn. Association of Official Analytical, Gaithersburg,
MD, USA (2000).
37 Vaast, Bertrand B, Perriot JJ, Guyot B and Génard M, Fruit thinning
and shade improve bean characteristics and beverage quality of
coffee (Coffea arabica L.) under optimal conditions. J Sci Food Agric
86:197– 204 (2006).
38 Geromel C, Ferreira LP, Guerreiro SMC, Cavalari AA, Pot D, Pereira LFP
et al., Biochemical and genomic analysis of sucrose metabolism
during coffee (Coffea arabica) fruit development. JExpBot
57:3243– 3258 (2006).
39 Wintgens JN (ed.). The Coffee Plant. Coffee: Growing, Processing, Sus-
tainable Production: A Guidebook for Growers, Processors,Traders, and
Researchers. Wiley-VCH, Weinheim, Germany, pp. 1–24 (2004).
40 Cortez J, Aptidão climática para a qualidade da bebida nas principais
regiões cafeeiras de Minas Gerais. Informe Agropecuário 18:27–31
(1997).
41 Camargo A, Santinato R and Cortez J, Aptidao climática para qualidade
da bebida nas principais regioes cafeeiras de café Arábica, in CON-
GRESSO Brasileiro de Pesquisas Cafeeiras, 18 Araxá (Brasil),27–30
Outubro 1992. Trabalhos Apresentados, Brazil (1992).
42 Bertrand B, Boulanger R, Dussert S, Laffargue A, Ribeyre F, Berthiot L
et al., Climatic factors directly impact the biochemical composition
and the volatile organic compounds fingerprint in green Arabica cof-
fee bean as well coffee beverage quality, in International Conference
on Coffee Science, pp. 628– 635 (2012).
43 Davis AP, Gole TW, Baena S and Moat J, The impact of climate change
on indigenous arabica coffee (Coffea arabica): predicting future
trends and identifying priorities. PLoS One 7:e47981 (2012).
44 Bunn C, Läderach P, Rivera OO and Kirschke D, A bitter cup: climate
change profile of global production of Arabica and Robusta coffee.
Clim Change 129:89 –101 (2015).
45 Oberthür T, Läderach P, Posada H, Fisher MJ, Samper LF, Illera J et al.,
Regional relationships between inherent coffee quality and growing
environment for denomination of origin labels in Nariño and Cauca,
Colombia. Food Policy 36:783–794 (2011).
46 Koshiro Y, Zheng XQ, Wang ML, Nagai C and Ashihara H, Changes in
content and biosynthetic activity of caffeine and trigonelline during
growth and ripening of Coffea arabica and Coffea canephora fruits.
Plant Sci 171:242 –250 (2006).
47 Joët L, Andréina , Salmona J, Doulbeau S, Descroix F, Bertrand B et al.,
Metabolic pathways in tropical dicotyledonous albuminous seeds:
Coffea arabica as a case study. New Phytol 182:146 –162 (2009).
48 De Castro RD and Marraccini P, Cytology, biochemistry and molec-
ular changes during coffee fruit development. Braz J Plant Physiol
18:175– 199 (2006).
49 Silvarolla MB, Mazzafera P, Lima MMAL, Caffeine content of Ethiopian
Coffea arabica beans. Genetics and Molecular Biology 23:213 – 215
(2000).
50 Ky CL, Louarn J, Dussert S, Guyot B, Hamon S and Noirot M, Caffeine,
trigonelline, chlorogenic acids and sucrose diversity in wild Coffea
arabica L. and C. canephora P. accessions. Food Chem 75:223 –230
(2001).
51 Bekele YD, Assessment of cup quality, morphological, biochemical
and molecular diversity of Coffea arabica L. genotypes of Ethiopia,
University of the Free State (2005).
52 Sridevi V and Parvatam G, Changes in caffeine content during fruit
development in Coffea canephora P. ex. Fr. grown at different eleva-
tions. JBiolEarthSci4:B168 –B175 (2014).
53 Bertrand B, Vaast P, Alpizar E, Etienne H, Davrieux F and Charmetant
P, Comparison of bean biochemical composition and beverage
wileyonlinelibrary.com/jsfa © 2016 Society of Chemical Industry J Sci Food Agric (2016)
Quality and biochemical composition of Ethiopian specialty coffee www.soci.org
quality of Arabica hybrids involving Sudanese-Ethiopian origins with
traditional varieties at various elevations in Central America. Tree
Physiol 26:1239– 1248 (2006).
54 Aerts RJ and Baumann TW, Distribution and utilization of chlorogenic
acid in Coffea seedlings. JExpBot45:497 –503 (1994).
55 Link JV, Lemes ALG, Marquetti I, dos Santos Scholz MB and Bona E,
Geographical and genotypic segmentation of arabica coffee using
self-organizing maps. Food Res Int 59:1 –7 (2014).
56 Avelino J, Barboza B, Davrieux F and Guyot B, Shade effect on
sensory and chemical characteristics of coffee from very high
altitude plantations in Costa Rica, in Second International Sympo-
sium on Multi-strata Agroforestry Systems with Perennial Crops,
17– 21 September 2007, Turrialba, Costa Rica, Turrialba, Costa Rica
(2007).
57 Dessalegn Y, Labuscagne M, Osthoff G and Herselman L, Variation
of green bean caffeine, chlorogenic acid, sucrose and trigolline
contents among Ethiopian Arabica coffee accessories. SINET: Ethiop
JSci30:77 –82 (2007).
J Sci Food Agric (2016) © 2016 Society of Chemical Industry wileyonlinelibrary.com/jsfa
