**3.1 Chemical composition of coffee**

Coffee has a number of chemical components, mainly water and dry matter, such as minerals, organic substances (carbohydrates, lipids, proteins), alkaloids (caffeine and trigonelline), carboxylic and phenolic acids, and volatile compounds responsible for the aroma. All together result in a great diversity and complexity of structures; however, these may have modifications in any of their stages, either from the crop or the mill [15].

The chemical composition varies depending on the species [16]. In the case of *Coffea arabica*, it has a higher lipid and sucrose content than *Coffea canephora*. The robusta differs by its higher content of polysaccharides, caffeine, chlorogenic acids, and ashes. **Table 2** shows the most representative chemical components in arabica and robusta species.

Additionally, within the varieties cultivated in Colombia are differences (see **Table 3**), due to the intrinsic factors, soil fertilization, atmospheric conditions, sowing density, and planting age, among others [15].

*Water*: The water content of the bean is one of the most relevant factors in all coffee processes, from germination to roasting. In the fresh fruit, the water content is between 70 and 80% [25]. After the dry process, the water content is reduced up to 10–12% to improve the stability and avoid microbial proliferation, prolonging its shelf life [16].

*Carbohydrates*: Among the main polysaccharides in coffee are mannan or galactomannan (polymer of mannose and galactose), constituting 50% of the polysaccharides, 30% of arabinogalactan (polymer of galactose and arabinose), 15% of cellulose (polymer of glucose), and 5% of peptic substances [16]. The beans in an optimum

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beans (0.044% in robusta coffee) [16].

*Coffee By-Products: Nowadays and Perspectives DOI: http://dx.doi.org/10.5772/intechopen.89508*

*\*Expressed in percentage, on a dry basis.*

**Coffee variety Fiber** 

*Chemical composition of the coffee beans of the arabica and robusta species.*

**Lipids (%)**

*Chemical composition of coffee bean in the different varieties sown in Colombia.*

**Proteins (%)**

Bourbon 21.75 15.27 13.90 1.15 7.37 3.78 Caturra 18.85 13.98 14.79 1.13 6.97 3.39

Colombia red fruit 16.69 14.27 13.92 1.19 7.42 3.52 Typica 18.71 13.99 14.59 1.20 6.66 3.43 Robusta 15.53 11.42 15.66 2.10 8.08 3.96

**Caffeine (%)**

18.45 13.07 14.45 1.16 7.55 3.49

**Chlorogenic acids (%)**

**Ash (%)**

**(%)**

*N.D. Non-determined.*

Colombia yellow

*Source: Puerta [16].*

fruit

**Table 3.**

**Table 2.**

**Chemical component\* Puerta [16] Echeverry et al. [17] Komes [18]**

Polysaccharides 50.8 56.40 38 41.5 N.D N.D Sucrose 8.00 4.00 N.D N.D N.D N.D Reducing sugars 0.10 0.40 N.D N.D N.D N.D Protein 9.80 9.50 10 1o N.D N.D Amino acids 0.50 0.80 N.D N.D N.D N.D Caffeine 1.20 2.20 1.3 1.4 0.76–1.82 1.51–3.33 Trigonelline 1.00 0.70 1 0.7 0.88–2.76 0.75–3.42 Lipids 16.20 10.00 17 11 N.D N.D Aliphatic acids 1.10 1.20 2.4 2.5 N.D N.D Chlorogenic acids 6.90 10.40 2.7 3.1 4–8.4 7–14.4 Minerals 4.20 4.40 4.5 4.7 N.D N.D Aromatic compounds Traces Traces 0.1 0.1 Traces Traces Melanoidins N.D N.D 23 23 25 25

**Arabica Robusta Arabica Robusta Arabica Robusta**

ripening stage have a higher sucrose content than defective and immature beans. In the arabica species, the sucrose content ranged between 6 and 9%, while robusta contains 3–7% of sucrose [16]. Monosaccharides and some disaccharides such as lactose and maltose may oxidize to form alcohols and acids in the fermentation process or may react with the amino acids in roasting to form melanoidins, which are responsible for the coloration (enzymatic browning) of the roasted coffee [16]. *Lipids*: Triglycerides, linoleic, and palmitic acid are mainly presents (~ 75% of coffee lipids). The unsaponifiable matter constitutes 20 to 25% of the lipids of coffee. Sterols are 2.2% of coffee lipids and contain β-sitosterol, stigmasterol, campesterol, and ∆5 avenasterol. Cholesterol constitutes 0.11% of the dry weight of coffee

*Nitrogen compounds*: Nitrogen constitutes between 1.30 and 3.23% of the dry weight of the green coffee beans, after the roasted decreased up to 1.51 and 2.14% [16].


*Coffee By-Products: Nowadays and Perspectives DOI: http://dx.doi.org/10.5772/intechopen.89508*

*\*Expressed in percentage, on a dry basis.*

*N.D. Non-determined.*

#### **Table 2.**

*Chemical composition of the coffee beans of the arabica and robusta species.*


#### **Table 3.**

*Chemical composition of coffee bean in the different varieties sown in Colombia.*

ripening stage have a higher sucrose content than defective and immature beans. In the arabica species, the sucrose content ranged between 6 and 9%, while robusta contains 3–7% of sucrose [16]. Monosaccharides and some disaccharides such as lactose and maltose may oxidize to form alcohols and acids in the fermentation process or may react with the amino acids in roasting to form melanoidins, which are responsible for the coloration (enzymatic browning) of the roasted coffee [16].

*Lipids*: Triglycerides, linoleic, and palmitic acid are mainly presents (~ 75% of coffee lipids). The unsaponifiable matter constitutes 20 to 25% of the lipids of coffee. Sterols are 2.2% of coffee lipids and contain β-sitosterol, stigmasterol, campesterol, and ∆5 avenasterol. Cholesterol constitutes 0.11% of the dry weight of coffee beans (0.044% in robusta coffee) [16].

*Nitrogen compounds*: Nitrogen constitutes between 1.30 and 3.23% of the dry weight of the green coffee beans, after the roasted decreased up to 1.51 and 2.14% [16].

*Alkaloids*: Alkaloids are the substances responsible for giving the bitter taste of coffee, the most representative are caffeine, trigonelline, paraxanthine, theobromine, and theophylline [16]. Caffeine is a methylxanthine, which have attributed health benefits, such as improve the central nervous, cardiovascular, respiratory, renal, and muscular system [19]. For the above statement, caffeine is important in the pharmaceutical industry. Also it has important bioactive properties, so it may be cataloged as a functional ingredient, which can be used in different food matrices [20].

*Chlorogenic acids*: They are a series of phenolic esters derived from the union of an ester between caffeic acid and quinic acid [3]. The chlorogenic acid content in green coffee is 7% and reaches 4% after roasting [3]. A volume of 200 mL of roasted and ground coffee could provide between 70 and 350 mg of chlorogenic acid [16]. Coffee beans contain more than 40 chlorogenic acids, especially esters of quinic acid such as CQA, di-CQA, and FQA [16]. This compound has a significant antioxidant capacity and also a stimulant, expectorant, diuretic, choleretic, and antihepatotoxic effects [21].

### **3.2 By-products of coffee processing**

The coffee bean is picked after reach the commercial ripening stage; it next must be quickly transformed into dry parchment coffee, to avoid accelerated fermentation because the entire bean includes high water and sugar content [22]. For these purposes the external layer is removed from the coffee bean and only 5% of the biomass is used to produce a coffee crop, the rest remains in a residual form as leaves, branches, green fruits, pulp, mucilage, parchment, and silverskin, among others [22]. There are two primary methods for processing coffee, to obtain green coffee (traded coffee beans): wet and dry. In the dry process, no layers are removed, and coffee cherries are laid out in the sun to dry. In the wet process, the fruit covering the layer is removed before they are dried. Approximately 40% of all coffee around the world is wet processed [23], because it is considered to produce superior tasting offers [8, 24]. In the wet process, it has been estimated that 40–45 L of wastewater are produced per kilogram of coffee [25].

In Colombia, the wet process has been implemented for decades, which generates a contamination of 115 g of COD per kilogram of cherry coffee [22]. To overcome this problem, new methods were developed; one of these is the Belcosub technology, in which the fruit is de-pulped. The external layer is transported without water, and the organic residues are reused; however, these do not generate a significant value. This system avoids up to 74% of the contamination of water resources, since less than 5 l/kg of dry parchment are used [22]. The most recent technology suggested by the National Federation of Coffee Growers is the ecological mill without dumping (Ecomil) that reduces the amount of water to 0.5 l of water per kilogram of dry parchment, implementing tanks generally in stainless steel that do not need water for coffee emptying. In addition, the water resulting from this process goes directly to purifying tanks with microorganisms and a series of filters that allow the water that falls to water sources to be clean and do not generate any pollution [22].

As mentioned above, a large amount of coffee bean components are removed. It is important to highlight that approximately 43.58% of the weight of the dried fruit are these by-products [22]. The valorization of these by-products through the recovery of bioactives has increasingly become of interest for food, pharmaceutical, and cosmetic industries [26–30].

A promising option to recover these bioactive compounds is the coffee pulp, which involves the epicarp and part of the mesocarp of the fruit. This by-product

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*Coffee By-Products: Nowadays and Perspectives DOI: http://dx.doi.org/10.5772/intechopen.89508*

Fresh and dried pulp Washing, drying, blending,

Fresh and dried pulp Mixtures of solvents with

Parchment Water extraction,

Fresh pulp Pretreatment with *Mycotypha*

Parchment Hydrolysis and

Fresh and dried pulp Co-digestion

Parchment Microwave and traditional

Parchment Composted parchment

Pulp Compost with *Trichoderma*

Husk Solid-state fermentation with

Husks Combustion furnace as well as

heating

hot water

**By-product Process Final use References** Fresh pulp Dried Biocomponents [40] Fresh pulp Chopped Animal feed [41, 42]

and freezing extracts with

ethanol and milli-Q water in different mixtures and sonication—maceration

Batch culture fermentation

concentration, and dried

Ethanol extraction mixed with temperature

sp. and biomethanization

Pretreatment with *Streptomyces* sp. and biomethanization

biomethanization

biomethanization

in a fluidized bed combustion chamber at pilot scale

Vermicomposting with *Eudrilus eugeniae* and *Trichoderma viride*

with a mixture of organic amendments, pulp with bovine manure, and the legume *Millettia ferruginea*

sp., *Streptomyces* sp. *Azotobacter* sp., and *Bacillus* sp.

As*pergillus* sp.

*Rhizopus, Phanerochaete*, and

bifidobacteria

Husk Supercritical carbon dioxide Extraction of caffeine [45]

Silverskin Subcritical water (25–270°C) Antioxidant activity [47]

Fresh pulp Fermentation Ethanol [51, 52] Fresh pulp and mucilage [53] Parchment Hydrolysis and fermentation [54]

Pulp and rejected grain [58]

Silage [43]

fiber

Biocomponents extraction, antioxidant activity, and bacterial inhibitory activity

Antioxidant activity, cytotoxicity on human epithelial gastric cells, and biocomponents profile

Prebiotic potential dietary

Inhibitory effect of a on hyaluronidase

Biocomponents extraction, antioxidant activity

Biogas [55]

Pyrolysis [64]

Compost [66]

Evaluate the reduction of caffeine and tannins

[44]

[46]

[48]

[49]

[50]

[56]

[57]

[59–63]

[65]

[67]

[68]

[69]

### *Coffee By-Products: Nowadays and Perspectives DOI: http://dx.doi.org/10.5772/intechopen.89508*



**Table 4.**

*Alternatives for added value of coffee pulp.*

contains significant amounts of caffeine and another component [31]. The reported chemical composition (expressed in dry mass) includes polyphenols (1.5–2.9%), total sugars (4.1%), protein (4–13.3%), lignin (17.5–19.3%), lipids (1.7–2.5%), cellulose (18–63%), total fiber (18–60.5%), ash (6–10%), tannins (1.8–9%), carbohydrates (44–89%), reducing sugars (12.4%), nonreducing sugars (2%), caffeine (1.2–1.5%), and chlorogenic acid (1.6%) [5, 31–33].

#### **3.3 Nowadays uses of coffee by-products**

Coffee consumption has increased significantly, which generates an increase in waste amount [32]. These wastes have pollution problems. Discharges of wastewater from industrial activities have become a global issue of concern [34]. Different alternatives to both mitigate the negative effects in the discharges of coffee by-products and generate added-value alternatives have been evaluated. For this purpose, different studies have been carried out to evaluate alternative uses and reduce the toxic effect on the environment [35].

According to CONAMA Resolution No. 430 from 05/13/2011, the concentration of phenols should be lower than 0.5 mg L<sup>−</sup><sup>1</sup> [36], due to when phenolic compounds are discharged into the environment will lead to the degradation process of organic materials difficult to degrade [37]. Coffee by-products are the polyphenols and also carbohydrates, proteins, and pectins, making them potential sources of agro-industrialization for various industries, as well as renewable economic resources that can be given a high added value [32]. **Table 4** presented alternatives for coffee by-product reuse.

Among the alternatives previously proposed for the food and nonfood industry, emphasis will be placed on the production of extraction of caffeine both from the beans and from the different by-products obtained.

Considering that caffeine is an alkaloid that possesses antioxidant capacity and increases energy availability, cognitive performance, and neuromuscular coordination, among others [38], one of the alternative uses of coffee and its by-products has focused on the extraction of this compound of functional interest, both for the food and nonfood sectors. However, in recent years, new extraction techniques have been sought in order to reduce the generation of waste, with a lower consumption of chemical reagents and therefore improve the efficiency of the process, reducing process times [39].
