Global Journey of Coffee: From Ethiopian Origins to Worldwide Cultivation

Coffee, one of the world's most beloved beverages, has its origins in Ethiopia, a country renowned for its rich cultural heritage and biodiversity. The coffee plant, Coffea arabica, is indigenous to the highlands of Ethiopia, where it thrived in the wild before being cultivated by humans. From Ethiopia, coffee began its journey across borders, initially spreading to the neighboring countries bordering the Red Sea. The Arabian Peninsula, including Yemen, played a pivotal role in the early trade of coffee, where it became an integral part of the local culture and was exported to other parts of the world through the port of Mocha.

The spread of coffee continued eastward to India and Sri Lanka, facilitated by traders and travelers who recognized its value both as a commodity and a beverage. However, it was during the era of European colonial expansion that coffee truly became a global phenomenon. European colonizers introduced coffee to their overseas territories, including Indonesia, Brazil, Colombia, El Salvador, the Philippines, and Mexico. These regions offered the ideal altitude and climate conditions for coffee cultivation, allowing the crop to flourish.

Today, Brazil stands as the largest coffee producer globally, contributing approximately 45% of the world's coffee supply. The country's vast plantations, particularly in regions like Minas Gerais and São Paulo, are responsible for producing a diverse range of coffee beans that cater to different tastes and markets. Colombia follows as the second-largest producer, with about 25% of global production, renowned for its high-quality Arabica beans. Mexico, though a smaller producer, still contributes 6% of the world’s coffee, with production concentrated in states like Chiapas and Veracruz. The remaining coffee production is distributed among numerous other countries in Central America, the northern part of South America, and Africa, each contributing unique flavors and characteristics to the global coffee market.

The coffee tree itself is a remarkable plant, bearing clusters of small, red, cherry-like fruits that each contain two seeds, commonly known as coffee beans. These fleshy berries are harvested almost continuously throughout the year, depending on the region's climate. After harvesting, the processing of coffee cherries varies based on local traditions and available resources. In some regions, the whole fruits are sundried, a method that enhances the sweetness and complexity of the beans. In others, the cherries undergo a short period of fermentation, which helps in removing the pulp from the seeds. Afterward, the greenish-yellow seeds are cleaned and sundried, eventually becoming the green coffee beans traded globally. These beans, when roasted and brewed, produce the rich, aromatic beverage enjoyed by millions worldwide.
Global Journey of Coffee: From Ethiopian Origins to Worldwide Cultivation

Properties of coffee beans

Coffee beans come from the coffee plant of Coffea arabica Linn. The tree bears clusters of small, red, cherry like fruit which contain two seed. The Arabica beans are generally oval in shape, have a pronounced centre crease and are larger than Robusta beans.

Once the beans are ripe and ready for picking, they will turn red in color. The fleshy berries are harvested almost continuously.

In the seeds, caffeine is present as a salt of chlorogenic acid (CGA). Also it contains oil and wax. Green coffee contained about 6–7% of sucrose as soluble sugars and low amount of glucose.

Depending on the growing region, the whole fruits are either sundried or they are allowed a short period of fermentation after which the pulp is removed from the greenish-yellow seed.

Before a cup of coffee is made, the coffee beans will undergo roasting, grinding, packing and transporting processes.

The quality of coffee used for beverages is strictly related to the chemical composition of the roasted beans, which is affected by the composition of the green beans and post-harvesting processing conditions (drying, storage, roasting and grinding).
Properties of coffee beans

Structure of coffee beans

A coffee bean is really 2 seeds that are side by side. Peaberry accounts for about 5% of the world’s coffee, has only a single bean inside the cherry, and is a natural mutation.

The coffee cherry's outer skin is called the exocarp. The exocarp, also referred to as the peel, skin, or epicarp, is the outermost layer of the coffee fruit. Beneath it is the mesocarp, a thin layer of pulp, followed by a slimy layer called the parenchyma.

Mesocarp is the “flesh” of the coffee fruit- during cherry maturation. This layer is rich in sugars and has a huge influence on the taste of the coffee bean.

Pectin is responsible in protecting the coffee beans. It’s made up of a cellulose layer.

The beans themselves are covered in a paper-like envelope named the endocarp, more commonly referred to as the parchment. This is a thick shell-like layer that surrounds the bean and is formed of three to seven layers of sclerenchyma cells (fibrous cells that serve as the principal support cells in plants). The cells of the endocarp harden during coffee fruit maturation, thus limiting the final size of the coffee seed, or bean.

Inside the parchment, side-by-side, lie two beans, each covered separately by yet another thin membrane. The biological name for this seed skin is the spermoderm, but it is generally referred to in the coffee trade as the silver skin. The silverskin is a very thin and fine layer of skin which envelops and adheres tightly to the seed of the fruit which is the coffee bean.

The endosperm is the primary reserve tissue of the seed and is composed of only one tissue though the cells in the outside and indoor part of the endosperm differ in oil material and cell wall density. Most of the coffee bean itself is comprised of endosperm, which is the tissue that is created near the time of fertilization in most flowering plants. The endosperm surrounds the embryo and supplies nutrition (starch) but may also contain proteins and oils.
Structure of coffee beans

Chemical constituents of coffee bean

Coffee is a main dietary source of polyphenol and phenolic acid. It is consumed by a million people because of its complex aroma and taste.

The coffee bean is composed of many components, including carbohydrate, proteins, lipids, tannin, polyphenols and minerals. It contains 2–3% caffeine, 3–5% tannins, 13% proteins, and 10–15% fixed oils. In the seeds, caffeine is present as a salt of chlorogenic acid (CGA). Also, it contains oil and wax.

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% w/w.

Nitrogen and potassium nutrition affects the chemical composition of the raw bean, which, after toasted, produces compounds that give aroma and flavor to the coffee.

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).
Chemical constituents of coffee bean

Moisture content of coffee bean

Coffee beans have a highly hygroscopic matrix, they could readily take up moisture when exposed to the atmospheric environment during storage. The investigation of water content and state on the textural properties of coffee beans could be of great interest in relation to the energy that has to be applied during grinding.

One of the principal postharvest processes is drying that gives rise to the formation of the characteristic color, flavor and taste of coffee brews.

There are many quality parameters for coffee trading. Among them, moisture content has been regulated as one of the quality standards for coffee green bean by most of importer and exporter countries. The appropriate range of moisture content is 8.0 to 12.5% based on fresh matter.

Green coffee that is high in moisture (greater than 12% wet basis) can deteriorate due to bacteria, mold, or yeast, especially if the seed is killed. If the seed remains alive, enzymatic activity will cause the cupping quality to change.

When the moisture content of the coffee bean is below 8%, it can be shrunken bean and unwanted physical appearance. In any case, the parchment coffee moisture level should be lowered to below 12% soon after harvest.

Therefore, an accurate and fast moisture content determination for the coffee bean is essential for the coffee sectors.

The coffee cherries are dried immediately after harvest. This is usually sun drying on a clean dry floor or on mats. The bed depth should be less than 40mm and the cherries should be raked frequently to prevent fermentation or discoloration.

The initial moisture content of harvested coffee is about 55-60% and after drying lowers the moisture content to around 12%.

When the ambient relative humidity is about 70 percent, coffee beans will gradually equilibrate to about 12 percent moisture. Thus green bean coffee is generally dried to 12 percent, and bought and sold at this moisture percentage.

After fermentation, the coffee is known as 'parchment coffee', since the seed retains its endocarp layer. It must be dried to about 10-12% (wb) moisture content to ensure stability.

The gravimetric method is widely accepted as a reference method to determine the moisture content for all coffee trading countries. A convenient sample size is 100 g initial weight. The samples are placed in the oven at 220°F for 24 hours. They are then weighed again (final weight). The difference between the initial weight and the final weight is the water, and it is also the percent moisture in the sample if started with 100 grams.

Alternative methods for rapid determination are also done and one of them is Near Infrared Spectroscopy (NIRS). NIRS is an increasingly growing non-destructive technique due to its rapidity, simplicity, and safety.
Moisture content of coffee bean

Protein in coffee beans

The nitrogen (N2) content of the coffee sample was determined on a Kjeldahl Digestion System. Protein content was calculated as nitrogen x 6.25.

The average protein content of coffee beans is 10%. The free amino acid content of green coffee beans shows a wide range, from 0.001% for methionine in Robusta to 0.1% for glutamic acid in Arabica.

Proteins are composed of different amino acids which are the main compounds contributing to the formation of the typical aroma during roasting, and previous studies have reported that alanine is the amino acid with the highest content (1.2 mg/g) in Robusta coffee beans, followed by asparagine (0.68 mg/g).

During roasting, volatile aromatic compounds and polymeric brown pigments are formed in the beans, while water and carbon dioxide are released. The principal thermally reactive constituents of the raw bean are the monosaccharides and sucrose, free amino acids, chlorogenic acids and trigonelline, and the newly formed precursors of degraded carbohydrates and denaturated proteins.
Protein in coffee beans

Coffee plant cultivation

Coffee plants are grown in greenhouses until they are a few inches tall. After about six months, they are transplanted into rows about three to ten feet (one to three meters apart on a coffee plantation.

A cultivated coffee plant is a small tree or a shrub. It consists of the three recognizable vegetative organs - stems, leaves and roots – common to most plants. It has a main trunks and horizontal branches that’s support its large, elliptical-shape leaves, which are dark green and shiny due to a waxy coating.

The coffee plant when regularly grown and pruned forms a very handsome bush, and in a state of health is well covered with dark green foliage.

Farmers normally regularly prune to about 12 to 15 feet high in order to make harvesting easier. During growing season, farmers inspect coffee plants for diseases such as leaf rust and for insect that damage the crops.

The leaves are from 3 to 5 inches long and nearly 2 broad, having a wavy margin and beautiful glossy appearance. A healthy, mature coffee bush may yield from 12 to 15 pounds of coffee cherries per year.

Arabica coffee grows best in tropical and subtropical areas of the world. In particular, coffee plants are adapted to warm climates with year-round temperatures about 70 ° F; at least 60 inches of rainfall a year. Robusta is more tolerant of warm temperatures and is cultivated in poorer soils closer to the equator.
Coffee plant cultivation

Category of coffee beans

The coffee beans that are commercially available can be divided into three categories:
*Mild coffees which are arabicas that were very carefully prepared. Their taste is mild, slightly acidic and pleasantly scented. Mild Arabica coffees are cultivated at altitudes over 2,000 feet above sea level, usually between 4,000 and 6,000 feet. They are produced from fruit that is picked only when ripe and prepared with care.

*Brazilian coffees, which are also arabicas, but are very diverse and have organoleptic characteristics are less appreciated. Brazilian Arabicas consists principally of Santos, Parana and Rio named after the ports from which they are shipped.

*African coffees canephora, which have a neutral taste that is less aromatic than previous ones. The robustas are full-bodies and are more bitter and bracing than the previous ones. Coffea canephora is indigenous to tropical West Africa (Benin, Burkina Faso, Cote d’Ivoire, Gabon, Gambia, Ghana, Guineas, Guinea-Bissau, Liberia, Mauritania, Niger, Nigeria, Senegal, Sierra Leone, Togo), eastwards to Uganda and north to south Cameroon to Northern Angola.

Both milds and Brazils come from trees that belong to the botanical species Coffee arabica. It still grows wild in Ethiopia and was first cultivated in commercial quantities in Yemen at the southern tip of the Arabian Peninsula.
Category of coffee beans

Chemical composition coffee beans

Coffee is a drink brewed from coffee beans that comes from the tropical shrub of the genus Coffea, botanically family Rubiaceae.

The quality of the coffee beans used to make coffee is directly related to their chemical composition. The constituents of coffee that are important in making a good beverage are the flavor substances, the bitter substance and caffeine which is responsible for the stimulating effects.

Compared with robusta green beans, arabica green beans have substantially higher lipid, sucrose and trigonelline contents but lower caffeine and chlorogenic acid (CGA) contents.

Caffeine is present in the coffee bean in both the free and combined states. Its content in the bean varies in different species – C. arabica contains 1.0 – 1.2; C. robusta 1.5 – 2.5 and C. liberica 1.4 – 1.6 per cent.

Caffeine, in addition to stimulation, also contributes to the bitterness of the coffee.

Several organic acids are present in the aqueous extract from green coffee beans, the predominant being chlorogenic acid and the least acetic acid.

Coffee beans contains between 8% and 18% (dry basis) fat depending on a variety and species. Green robusta beans generally have lower lipid contents than arabica coffee beans.

Around 75% of coffee oil is in a triglyceride form, with linolenic and palmitic acids being the main fatty acids.

The composition of roasted coffee will vary according to the raw material, roasting degree and roasting parameters such as time, temperature and speed in which the process occurs.
Chemical composition coffee beans

Physical properties of coffee beans

Coffee is the roasted kernel of the coffee cherry.  Each coffee bean is actually the seed of a coffee cherry, the fruit of the coffee tree.

In the coffee process, first the fruit flesh (pulp and parchmentlike hull) is removed, and then the kernel is dried, resulting in green coffee beans.

A typical coffee bean has the shape of a half ellipsoid with well rounded edges.  It contains about 12% of water and most of this is lost in the early stage of roasting, followed by a loss of up to 8% of the dry bean material.

The green coffee bean has a very tight structure where less than 7% of its pore volume has a diameter of 10 nm or more.

The two coffee beans are covered by a thin parchmentlike hull, which is further surrounded by pulp.
Physical properties of coffee beans

Coffee Plant and World Production

Coffee Plant and World Production
The coffee plant belongs to the genus Coffea in the Rubiaceae botanical family. Although there are numerous species, only two of them are used for cultivation world wide: Coffea arabica L. and Coffea canephora. Coffea robusta is a variety of Coffea canephora. Coffea excelsa, cultivated in Central Africa, is one of the numerous varieties of Coffea dewevrei; its total production is much smaller than that of the previous cited species.

The height of adult coffee trees ranges form one foot to fifty feet, depending on the species. There are numerous varieties of coffea arabica, which originated in Ethiopia. This coffea grows at altitudes between 3250-6500 feet in Latin America, Reunion Island and Indonesia; this species represents 75% of coffea production world wide. Coffea canephora, second in production, is mainly grown in Africa and Indonesia. The most common variety is robusta (95% of plantation of Coffea canephora). It is cultivated in Africa, in Far East, South Sea Islands and in Brazil in regions where arabica cannot be grown because of climatic condition.

The trunk of the coffee is straight and smooth, its branches hang low and slope downwards, the leaves are green, elongated and non-deciduous. White blossoms (fragrant star shaped flowers that last only a few days) along with green, yellowing or red fruit coexist on the same branch. The fruit looks like cherries; its contains two seeds that will become coffee beans, Arabica coffee beans are oval and long with a subtle taste and fruit-like aroma while robusta beans are smaller, round, irregular, and have a stringer taste.

The word ‘drupe’ is the technical term used to designate the fruit. It matures in six to fourteen month, depending on the variety; the fruit is covered by a very tough skin-like, smooth red film called the ‘epicarp’. It covers the ‘mesocarp’ which contains mostly water (70 to 85%) and has a high concentration of sugar and pectin. The ‘mesocarp’ represents 40 to 65% of the fruit’s weight, depending on the variety, The bean is formed of a horn-like albumen (endosperm) made up of starch, lipids, reducing sugars, sucrose, tannins, caffeine, etc, and 20% water. Two envelopes cover the endosperm, one is internal: the ‘spermoderm’ or ‘silverskin’; the other external, the ‘endocarp’ or parchment.
Coffee Plant and World Production

Arabica Coffee Beans

Arabica Coffee Beans
There are about 20 major species within coffee, but the typical coffee beverage is likely to be familiar with just two: Coffea Arabica and Coffea Robusta. Arabica is autogamous. That is to say, capable of fertilizing itself, whereas Robusta us allogamous.

Arabica coffee beans or coffea Arabica species originated from Yemen and Ethiopia during pre-historic times. Also known as mountain Coffea Arabica, Coffea Arabica is now grown throughout Latin America, Central and East Africa, India and in some parts of Indonesia. The plant can only be grown in a tropical or subtropical climate.

Arabica coffee bean is considered better than any other coffee in the world and to be highest quality among. It is believed that coffea Arabica is the first species of coffee to be cultivated. The plant produces a small, bean sized fruit that ripens from a green color to a dark coffee bean. Coffea Arabica has a wide tasting range that will depend on its varieties. Coffea Arabica can have a sweet-soft taste and it can also have a sharp-tangy taste. Generally, pure Arabica blends are the best tasting coffee, a fact that is reflected in its higher price.

Coffea Arabica contains less caffeine than any other commercially cultivated. Coffea Arabica represents approximately 75 – 80% of the world’s coffee production. The plant is an evergreen, typically large bush with dark green that can reach height up to 20 feet.

Today, Americans are rediscovering the glories of coffee due to the rising popularity of coffee shops. Now coffee is not as simple as it was in the past. The rise of shops like Starbucks has created a whole new experience around the humble cup of coffee.
Arabica Coffee Beans