REVIEW PAPER
Production, Composition, and Application of Coffee
and Its Industrial Residues
Solange I. Mussatto & Ercília M. S. Machado &
Silvia Martins & José A. Teixeira
Received: 9 March 2010 /Accepted: 16 March 2011 /Published online: 31 March 2011
#
Springer Science+Business Media, LLC 2011
Abstract Coffee is one of the most consumed beverages
in the world and is the second largest traded commodity
after petroleum. Due to the great demand of this product,
large amounts of residue s are gener ated in the c offee
industry, which are toxic and represent serious environ-
mental problems. Coffee silverskin and spent coffee
grounds are the main coffee industry residues, obtained
during the beans roasting, and the process to prepare
“instant coffee”, respectively. Recently, some attempts
have been made to use these residues for energy or
value-added compounds production, as strategies to
reduce their toxicity levels, w hile adding value to them.
The present article provides an overview regarding coffee
and its main industrial residues. In a first part, the
composition of beans and their processing, as w ell as
data about the coffee world production a nd exportation,
are presented. In the sequence, the characteristics,
chemical composition, and application of the main
coffee industry residues are reviewed. Based on these
data, it was concluded that coffee may be considered as
one of the most valuable primary products in world
trade, crucial to the economies and politics of many
developing countries since its cultivation, processing,
trading, transportation, and marketing provide employ-
ment for millions of people. As a consequence of this
big market, the reuse of the main coffee industry
residues is of large importance from environmental
and economical viewpoints.
Keywords Coffee
.
Silverskin
.
Spent grounds
.
Cellulose
.
Hemicellulose
Introduction: The Coffee History
Coffee has been consumed for over 1,000 years and
today it i s the most consu med drink in t he world (more
than 400 billion cups yearly) (Sobésa Café 2008). Arabia
was responsible for the coffee cul ture propagation. The
most ancient manuscripts mentioning the culture of
coffee date from 575 in Yemen, but only in the century
XVI in Persia, the first coffee beans were toasted to be
turned into the drink that we know today (Neves 1974).
Coffee began to be savored in Europe in 1615, brought
by travelers. Ge rmans, Frenchme n, and Italians were
looking for a way of developing the plantation of coffee
in their colonies. But it was the Dutchmen who got the first
seedlings and who cultivated them in the stoves of the
botanical garden of Amsterdam, a fact that made the drink
one of the most consumed in the old continent and
becoming a definitive part of the habits of the Europeans.
Next, the Frenchmen were given a plant of coffee by the
major of Amsterdam, and they began to cultivate in the
islands of Sandwich and Bourbon (Neves 1974). With the
Dutch and French experiences, the coffee cultivation was
taken to other European colonies. The European market
growth favored the expansion of the plantation of coffee in
African countries and was also through the Europ ean
colonists that c offee reached Puerto Rico, Cuba, Suriname,
São Domingos, and Guianas. Through the Guianas, coffee
S. I. Mussatto (*)
:
E. M. S. Machado
:
S. Martins
:
J. A. Teixeira
IBB—Institute for Biotechnology and Bioengineering,
Centre of Biological Engineering, University of Minho,
Campus de Gualtar,
4710-057 Braga, Portugal
e-mail: solange@deb.uminho.pt
e-mail: solangemussatto@hotmail.com
Food Bioprocess Technol (2011) 4:661–672
DOI 10.1007/s11947-011-0565-z
arrived to the north of Brazil. Then, the secret of the Arabs
was spread by the enti re world (Taunay 1939).
The coffee tree or shrub belongs to the f amily
Rubiaceae. Coffee beans are produced from the plant
Coffea L., of which there are more than 70 species.
However, only two of these species are commercially
explored worldwide: Coffea arabica (Arabica), considered
as the noble st of all coffee plant s and providin g 75% o f
world’s production; and Coffea canepho ra (R obusta) ,
considered to be more acid but more resistant to plagues,
and provides 25% of world’s production (Belitz et al. 2009;
Etienne 2005). C. arabica is a bush originally from Ethiopia
and develops well in high altitudes (600–2, 000 m), while
C. canephora plantations adapt well in altitudes below
600 m (Comité Français du Café 1997).
Coffee Beans Processing
Coffee cherries are the raw fruit of the coffee plant , which
are composed of two coffee beans covered by a thin
parchment like hull and further surrounded by pulp (Fig. 1).
These cherries are usually harves ted after 5 years of coffee
trees plantation and when the bear fruit turns red (Arya and
Rao 2007). The processing of coffee initiates with the
conversion of coffee cherri es into green coffee beans, and
starts with the removal of both the pulp and hull using
either a wet or dry method. Depending on the method of
coffee cherries processing, i.e., wet or dry process, the solid
residues obtained have different terminologies: pulp or
husk, respectively (Pandey et al. 2000). The dry method,
commonly used for Robusta, is technologically simpler
comparing with the wet method, which is generally used for
Arabica coffee beans. In wet coffee process, the pulp and
hull are removed while the cherry is still fresh. This process
involves several stages that comprise considerable amounts
of water and also includes a microbial fermentation step in
order to remove any mucilage still attached to the beans.
The production of microbial volatile compounds during
fermentation results in coffee with richer aroma quality
(Gonzalez-Rios et al. 2007a, b). The quality evaluation of
green coffee is based on odor and taste tests, as well as on
the size, shape, color, hardness, and presence of defects
(Feria-Morales 2002).
The roasting of coffee beans is another very important
step in coffee processing, since specific organoleptic
properties (flavors, aromas, and color) are developed and
affect the quality of the coffee and the excellence of the
coffee beverage, as a consequence (Hernández et al. 2008;
Franca et al. 2005; Fujioka and Shibamoto 2008). This
process is time–temperature dependent and leads to several
changes in the chemical composition and biological
activities of coffee as a result of the transformation of
naturally occurring polyphenolic constituents into a complex
mixture of Maillard reaction products (Czerny et al. 1999;
Sacchetti et al. 2009), as well as the formation of organic
compounds resulting from pyrolysis (Daglia et al. 2000).
Sulfur compounds are also changed by oxidation, thermal
degradation, and/or hydrolysis (Kumazawa and Masuda
2003), and the vanillin content increases considerably during
the roasting process (Czerny and Grosch 2000). Besides the
chemical reactions during coffee roasting, moisture loss
and other major changes (color, volume, mass, form, pH,
density, and volatile components) occur, while CO
2
is
generated (Hernández et al. 2008). Therefore, coffee roasting
is a quite complex process considering the importance of
the heat transferred to the bean (Franca et al. 2009a).
After the roasting process, coffee beans should be rapidly
cooled in order to stop exothermic reactions and to prevent
excessive roast, which might jeopardize the product
quality ( Baggenstoss et al. 20 07;Dutraetal.2001).
Subsequently, the roasted beans are ground, usually by
multi-stage grinders. Some roasted beans are packaged
and shipped as whole beans. Finally, the ground coffee is
vacuum sealed and shipped.
If the objective is producing instant coffee, an additional
step of e xtraction follows the roasting and grinding
operations. The soluble solids and volatile compounds
that provide aroma and flavor are extracted from the
coffee beans using water. Water heated to about 175 °C
under pressurized conditions (to maintain the water as
liquid) is used to extract all of the necessary solubles
from the coffee beans. Manufacturers use both batch and
continuous extractors. Following extraction, evaporation
or freeze co nc ent ra tion is used to increase the solubles
concentration of the extract (EPA 2010). The concentrated
extracts are then dried; freeze drying and spray drying
being the most frequently used methods to produce
instant coffee. In the freeze-drying method, the concen-
pluPnikS
Parchment
Bean
Silverskin
Fig. 1 Longitudinal cross-section of the coffee cherry
662 Food Bioprocess Technol (2011) 4:661–672
trated coffee ex tr act is initially frozen a nd then milled.
Next, the frozen granul es are s ift ed before drying to
ensure uniform sizes. In this p rocess, few changes in
aroma are caused by heating and oxidation since the
moisture is sublimed in a vacuum chamber. When spray-
drying method is used, concentrated coffee extract is
atomized in a drying chamber from which the wat er is
removed due to the contact with air at temperatures
between 200 and 300 °C. This technique allows large-
scale production and provides products with low d ensity
and good flowabi lity. Sensory evaluations of different
commercial instant coffee revealed that the quality
attribute is associated with the beans, storage time,
fermentation process, roasting, extraction of the soluble
solids, and the packaging material (Oliveira et al. 2009).
Chemical Composition of Coffee Beans
Caffeine is the most known component of coffee beans. In
raw Arabica coffee, caffeine can be found in values varying
between 0.8% and 1.4% (w/w), while for the Robusta
variety these values vary between 1.7% and 4.0% (w/w)
(Belitz et al. 2009). However, coffee bean is constituted by
several other components, including cellulose, minerals,
sugars, lipids, tannin, and polyphenols. Minerals include
potassium, magnesium, calcium, sodium, iron, manganese,
rubidium, zinc, copper, strontium, chromium, vanadium,
barium, nickel , cobalt, lead, molybdenum, titanium, and
cadmium. Among the sugars, sucrose, glucose, fructose,
arabinose, galactose, and mannose are present. Several
amino acids such as alanine, arginine, asparagine,
cysteine, glutamic a cid, glycine, histidine, isoleucine,
leucine, lysine, methionine, phenylalanine, proline, serine,
threonine, tyrosine, and valine can also be found in these
beans (Belitz et al. 2009; Grembecka et al. 2007; Santos and
Oliveira 2001). Additionally, coffee beans contain vitamin of
complex B, the niacin (vitamin B3 and PP), and chlorogenic
acid in proportions that may vary from 7% to 12%, three to
five times more than the caffeine (Belitz et al. 2009;Lima
2003; Trugo 2003; Trugo and Macrae 1984). Table 1 shows
the chemical composition of coffee beans from Arabica and
Robusta varieties.
Among the substances present in the chemical compo-
sition of coffee, only caffeine is thermostable, i.e., it is not
destroyed by excessive roasting. Other substances such as
Table 1 Chemical composition of green coffee
Component Arabica
a
Robusta
a
Constituents
Soluble carbohydrates 9–12.5 6–11.5
Monosaccharides 0.2–0.5 Fructose, glucose, galactose, arabinose (traces)
Oligosaccharides 6–93–7 Sucrose (>90%), raffinose (0–0.9%), stachyose (0–0.13%)
Polysaccharides 3–4 Polymers of galactose (55–65%), mannose (10–20%), arabinose (20–35%),
glucose (0–2%)
Insoluble polysaccharides 46–53 34–44
Hemicelluloses 5–10 3–4 Polymers of galactose (65–75%), arabinose (25–30%), mannose (0–10%)
Cellulose, β(1–4)mannan 41–43 32–40
Acids and phenols
Volatile acids 0.1
Nonvolatile aliphatic acids 2–2.9 1.3–2.2 Citric acid, malic acid, quinic acid
Chlorogenic acid 6.7–9.2 7.1–12.1 Mono-, dicaffeoyl-, and feruloylquinic acid
Lignin 1–3
Lipids 15–18 8–12
Wax 0.2–0.3
Oil 7.7–17.7 Main fatty acids: 16:0 and 18:2 (9,12)
N compounds 11–15
Free amino acids 0.2–0.8 Main amino acids: Glu, Asp, Asp-NH
2
Proteins 8.5–12
Caffeine 0.8–1.4 1.7–4.0 Traces of theobromine and theophylline
Trigonelline 0.6–1.2 0.3–0.9
Minerals 3–5.4
From Belitz et al. (2009)
a
Values in percent dry-weight basis
Food Bioprocess Technol (2011) 4:661–672 663
proteins, sugars, chlorogenic acid, trigonelline, and fat may
be preserved or even de stroyed a nd transfo rmed into
reactive products during the coffee roasting process
(Ginz et al. 2000;Lima2003; Rawel and Kulling 2007;
Trugo 20 0 3; Trugo and Macrae 1984).
Coffee Beans Brewing
“Coffee” is the designation o f the drink prepared by
extraction, in boiling water, of the soluble material from
roasted coffee grounds. There are many different coffee
brewing methods in the world. Coffee beverage can be
prepared, for example, by filtration–percolation met hod,
where ground coffee is placed on a specific support grid
(filter paper, muslin, perforated plastic filter, sintered glass,
etc.) and the coffee is extracted by dripping or spraying
with hot water, i.e., by slow gravity percolati on. This
procedure is generally used in most coffee machines. In an
Espresso machine, used to produce the traditional Italian
coffee beverage called Espresso, coffee is extracted using
superheated water (90±5 °C), and filtration is accelerated
by steam at a pressure of 7–9 bar for a short time (30±5 s)
(Petracco 2001). An exceptionally strong beverage is
usually turbid, and is prepared with freshly ground and
darkly roasted coffee. In this process, the water should not
exceed 90–95 °C so that the volatile substances are retained
in the coffee beverage (Belitz et al. 2009; Navarini and
Rivetti 2010 ).
The most popular coffee brew preparation is by filter,
but during the past few decades the consumption of
espresso coffee has increased. Moreover, in southern
European countries such as Italy and Spain, the use of
the mocha coffeemaker is much extended at the domestic
level, and the plunger coffeemaker is being used more
often for coffee aroma lovers (Pérez-Martínez et al.
2010). In each case, the technical conditions applied, such
as th e coffee/water ratio, water temp eratu re and pressure,
the volume of coffee prepared, and the home and store
grinding, contribute to the different chemical compositions
of coffee brew s (An due za et al. 2002, 2003, 2007;Bellet
al. 1996; Franková et al. 2009; Navarini et al. 2009;Parras
et al. 2007; Ratnayake et al. 1993). For example, the
mocha coffeemaker was found to present the highest yield
in coffee a ntio xi dant extraction per gram of grou nd roasted
coffee when compared with coffee brews prepared by
filter, plunger, or espresso, but espresso coffee was the
richest in terms of antioxidant intake (per milliliter of
coffee brew) followed by mocha, plunger, and filter
(Pérez-Martínez et al. 2010). Filt ered coffee brews were
reported as containing less than 7 mg of lipids, whereas
those prepare d by b oilin g without filt ering and espresso
coffee may reach up to 160 mg of lipids per cup
(Ratnayake et al. 1993).Thecaffeinecontentinthecoffee
drinkalsovaryaccordingtotheusedbrewingprocedure,
being observed a considerable increase on caffeine
yields when higher amounts of coffee grounds and
volumes of coffee prepared are used. Depending on the
length of coffee boiling time, similar or higher caffeine
contents can be found when comparing with filtered
coffee (Bell et al. 19 96).
The water quality plays also a crucial role in coffee
brewing, being considered as the second most important
ingredient for coffee brewing. Water with an altered
composition, such as some mineral spring waters,
excessively hard water, and chlorinated water, might
reduce the quality of the coffee brews (Belitz et al. 2009;
Navarini a nd Rivetti 2010 ). Besides water, the pH of
brewed coffee is another fac tor wit h great in fluenc e on the
flavor characteri sti cs of the coffee bevera ge. For pH valu e
lower than 4.9, coffee brews presents a s our taste, and
higher than 5.2 it is flat and bitter. Therefore, the pH value
usingmildroastedcoffee(42.5g/l)shouldbe4.9–5.2.
Coffees of different origins provide extracts with different
pHs, an d, general ly, the pHs of Robusta varieties are
higher than those of Arabica varieties. The difference
between the aroma q ualities of the coffee beverage is due
to more intensive phenolic, buttery, caramel-like, and
weaker roast y notes, which are caused by shifts in the
concentrati ons of the aroma substa nc es during brew ing
(Bell et al. 1996).
Coffee World Production and Exportation
Worldcoffeeproductionhasgrownmorethan100%
from 1950 to 1960, and there was a prediction to grow
more 0.5–1.9% by 2010 (Fujioka and Shibamoto 2008).
Coffee is nowadays produced in a large number of
countries worldwide. Nevertheless, the ten largest co ffee-
producing countries are responsible for approximately
80% of the world production. Of this percentage, South
America participates with around 43%, Asia w ith 24% ,
Central America 18%, and Africa with 16%. Brazi l,
Vietnam, Colombia, and Indonesia are respectively the
first, second, and third largest world producers, responsible
for more than half of the world supply of coffee (Table 2).
According to the International Coffee Organization (ICO
2010), in 2009 Brazil produced approximately 40 million
bags of coffee (Table 2).
The world co nsum pti on o f c offee in 2 007 , es timate d
by the International C offee Organization, has been
around 124,636 million bags of 60 kg, representing an
increase of 2.88% regarding the 121,150 million sacks
consumed in 2006 (ICO 2010). Despite the fin anci al
crisis, the world consumption of coffee in 2008 was
664 Food Bioprocess Technol (2011) 4:661–672
around 128 million bags. According to ICO, the consum p-
tion of coffee w as not affected by the crisis. The
consumers will not stop drinking coffee, but instead of
drinking high quality coffee, peop le w ill start to take
coffee of middle quality.
Regarding the exportation, the quantity of coffee
exported has been on average at 90.0 million bags of
60 kg per year, with Brazil leading exportations with a
share of 28% of this market (Table 3).
Residues Generated in the Coffee Industry
The generation of residues and by-products is inherent in
any productive sector. The agro-industrial and the food
sectors produce large quantities of waste, both liquid and
solid. Coffee is the second largest traded commodity in the
world, after petroleum, and therefore, the coffee industry is
responsible for the generation of large amount of residues
(Nabais et al. 2008). In the last decade, the use of such
Countries Production
2004 2005 2006 2007 2008 2009
Brazil 39.272 32.944 42.512 36.070 45.992 39.470
Vietnam 14.370 13.842 19.340 16.467 18.500 18.000
Colombia 11.573 12.564 12.541 12.504 8.664 9.500
Indonesia 7.536 9.159 7.483 7.777 9.350 9.500
Ethiopia 4.568 4.003 4.636 4.906 4.350 4.850
India 4.592 4.396 5.159 4.460 4.372 4.827
Mexico 3.867 4.225 4.200 4.150 4.651 4.500
Guatemala 3.703 3.676 3.950 4.100 3.785 4.100
Peru 3.425 2.489 4.319 3.063 3.872 4.000
Honduras 2.575 3.204 3.461 3.842 3.450 3.750
Côte d’Ivoire 2.301 1.962 2.847 2.598 2.353 1.850
Nicaragua 1.130 1.718 1.300 1.700 1.615 1.700
El Salvador 1.437 1.502 1.371 1.621 1.547 1.500
Other countries 15.713 15.779 16.019 16.138 15.680 15.455
Total 116.062 111.463 129.138 119.396 128.181 123.002
Table 2 Annual worldwide
coffee production
(million bags of 60 kg)
From ICO (2010)
Countries Exportation
2003 2004 2005 2006 2007 2008
Brazil 25.670 26.653 25.956 27.642 28.010 29.486
Vietnam 11.631 14.859 13.432 14.001 17.936 18.417
Colombia 10.244 10.194 10.871 10.945 11.115 12.300
Indonesia 4.795 5.460 6.744 5.280 4.149 4.000
Ethiopia 2.229 2.491 2.435 2.935 2.604 2.500
India 3.707 3.647 2.823 3.699 3.259 3.300
Mexico 2.595 2.361 1.985 2.570 2.912 3.000
Guatemala 3.821 3.310 3.466 3.312 3.726 3.800
Peru 2.503 3.184 2.369 3.881 2.879 3.730
Honduras 2.425 2.779 2.392 2.898 3.312 3.000
Côte d’Ivoire 2.647 2.573 1.819 2.402 2.582 2.600
El Salvador 1.304 1.328 1.280 1.293 1.210 1.200
Nicaragua 1.013 1.311 1.003 1.445 1.259 1.200
Other countries 11.398 10.522 10.613 9.806 1.191 1.191
Total 85.982 90.672 87.188 92.109 96.367 96.622
Table 3 World exportation
of coffee (million bags of 60 kg)
From ABIC (2009)
Food Bioprocess Technol (2011) 4:661–672 665
