HomeFrom the Plant to Your Cup
Cultivation
The cultivation, care and harvesting of coffee is extremely labour intensive. It begins with the sowing. Coffee seeds will only germinate if sown within the eight weeks following the harvest. They are sown one to two cm deep in specially constructed beds.
After five to eight weeks the tiny plants reach the surface. As soon as the first pair of leaves appear, sometimes even sooner, the seedlings are transplanted to special foil planting bags, so called polycovers, or often to peat pots. They are then set 20 to 25 cm apart in large, predominantly shaded beds.
Six months later the young plants are 30 to 50 cm tall. At this stage they are transplanted to their final place in the coffee plantation, now at a distance of one to three metres apart. Here, the plants are usually protected by Guamos, trees which shade the plants from intense sunlight.
The newer varieties of coffee tree begin to bear fruit from the third or fourth year and go on to produce an optimal crop for ten years. Older varieties produce their first harvest after five years, but continue to produce maximum crops for 25 years.
Harvesting
Around nine months after the flowers appear, the berries are ripe and can be harvested. Harvesting is mainly carried out by hand.
The main harvesting season lasts around four months for Arabica coffee, and for Robusta coffee a little longer. In some countries, however, there is no standard harvesting season because of the significant climatic and geographical differences. In Colombia for example, harvesting continues throughout the year.
There are two reasons for the length of the main harvest of Arabica coffee, which can last for up to four months. Firstly, the speed at which the coffee berries ripen varies from tree to tree. And secondly, the coffee tree is unusual in that blossom, unripe and ripe berries can all be found on the same branch.
There are three methods of picking:
- Hand-picking (also called selective picking)
- Strip-picking
- Mechanical harvesting
Hand-picking
Higher quality Arabica beans are almost always hand-picked. Allthough this is a more expensive method of harvesting, it ensures that only ripe, high quality berries are picked. The workers go between the trees and selectively pick only the cherries that are at the peak of maturity. Hand-picking is the most labour-intensive harvesting method.
Coffee cherries are at their peak for only a few days before they turn overripe, so workers must go over each tree many times. On a single day a coffee picker harvests on average between 50 and 100 kg of coffee berries.
Strip-picking
In Brazil, and for the Robusta coffees cultivated in Africa and Indonesia, the coffee berries are not picked individually. Here, the pickers strip the branch of all the berries, both ripe and unripe, with one sweep of the hand. The berries, together with torn leaves and twigs, fall on the ground beneath the trees, onto large cloths, from which the harvest is later gathered. This method of harvesting is used for cheaper, commercial Robusta beans and causes some of the flavour taints associated with lower quality coffees.
Mechanical harvesting
On large plantations in Brazil harvesting machines are sometimes used, which shake all the berries from the tree.
Processing
The two coffee beans make up only one third of the coffee berry, the rest consisting of fruit flesh (also known as pulp), skin and husk, all of which must be removed so that only the green beans remain.
Two different methods of processing the coffee beans have now been adopted worldwide: wet processing and dry processing.
Wet processing
Wet processing, whereby the beans are washed, is mainly employed in Central America and parts of Africa (notably Kenya). This process is relatively expensive, but is beneficial to the quality of the coffee. The berries are first fed through a water channel to soak them and to remove any impurities. The unripe berries sink to the bottom, leaving the ripe fruit to float to the top.
The ripe berries can then be processed further. The fruit flesh of the berries is removed with the help of a 'de-pulper', a machine that has a roller with a roughened surface. This scours away the fruit flesh (pulp) from the berries under a stream of water. Previously, the remaining pulp was treated as waste, but nowadays it is blended with minerals and turned into fertiliser.
In the second stage of wet processing the coffee beans are fermented in large water containers. The object of the fermentation process is not only to dissolve any remaining fruit flesh, but also to remove the sticky film surrounding the coffee beans, which is not water soluble. This part of the procedure, which lasts approximately two days, is very important. The long period of fermentation is what first gives the coffee its rich aroma and special flavour.
Washing
On completion of the fermentation process the coffee beans have to be washed. At this stage, the beans are still surrounded by their parchment husk, and for this reason the coffee is also referred to as 'parchment coffee'.
Drying
The washed parchment coffee is then spread out on concrete slabs or drying racks and left out in the sun. To ensure that the beans dry evenly they are turned over several times a day. Depending on the weather conditions, this process takes five or six days.
Cultivators operating on a medium to large scale make use of drying machines, huge metal drums inside which hot air circulates. Again, to ensure that the beans dry evenly the drums rotate continually. In the drums the drying process lasts about 24 hours. Dried parchment coffee has an attractive golden yellow colour and is known as pergamino coffee.
At this stage the work of the coffee cultivators is largely at an end. The producer parts with his product, selling it to a wholesale distributor and/or an exporter.
Hulling
Next the pergamino is stored in bags, before being mechanically hulled by special machines. These peeling machines have grooved cast iron cylinders, inside which the husk of the coffee beans is scoured away as they rub against one another.
At the end of this process the beans are generally olive green in colour. Some varieties even have blue beans; these are the high quality so-called 'blue' coffees.
Sorting and grading
First the coffee beans are sieved to remove any foreign objects and damaged beans. Next they are mechanically graded according to size and shape. This is followed by a further selection process, this time carried out by trained workers. The coffee is sorted by eye as it passes in front of them on a conveyor belt into the different quality grades. There are also machines now that can perform this selection work.Dry processing
In Brazil and across a large part of Africa, dry processing is used for lower quality Arabica and Robusta berries, a simple technique which is less labourintensive than wet processing. However, cheaper production costs must be offset against a loss in quality, since the length of the process (the drying of the berries) is dependent on the unpredictable climate. Once all twigs, leaves, stones and other foreign objects have been sieved out, dry processing can begin.
Drying
The berries are spread out in the sun on cement or brick slabs in layers five to six cm deep. To ensure that the beans dry evenly, the berries are turned regularly for a period of two to three weeks. On smaller plantations drying mats made of wire netting are often used.
Hulling
Once the beans are completely dry, hulling begins. In a peeling machine similar to that used during wet processing, the dried fruit flesh (the pulp), the parchment skin and a part of the husk that surrounds the coffee bean are removed.
Cleaning and selecting
Finally, the beans are cleaned and then sorted according to size by mechanically operating vibrating sieves. The beans are then measured into sacks of a standard size (usually 60 kg).
Inspection and storage
The sorted coffee is packed in sisal bags each holding 60 kg (70 kg in Colombia). The final stage in the process is inspecting the coffee. A sample is taken from a large number of sacks. These samples are then examined, roasted, ground and separately numbered by expert inspectors before being brewed. After the experts have examined and tasted the samples, they deliver their verdict. The bags are given a quality seal and can then be exported.
Grading standards
Each producing country sets its own standards for grading, and the criteria used for grading vary from country to country. The governments of many coffee-growing countries impose strict grading standards to maintain consistent quality and preserve the reputation of coffees grown in those countries.
In addition, coffee is sometimes graded by the number of imperfections (stones, broken or deformed beans, twigs, etc.) per kilogram. Less than 20 percent of beans are of high enough quality to be considered speciality coffee.
Bulk transport
The majority of the coffee is shipped direct from the country of origin to the country of consumption. Previously, the sacks were piled up one by one in the ship's hold, but nowadays container transport is used. The newest form of transport is that of bulk transport, whereby the coffee is stored loose in the container.
Storage periods
Once dried, the green coffee can be stored for about a year without appreciable deterioration in quality. Green coffee of up to a year old is designated 'current crop'. Longer storage times alter the quality of the coffee, as the beans become drier. They are then marketed as 'past crop' or 'old crop'.
Espresso Roasting
Roasting is a chemical process by which aromatics, acids, and other flavor components are either created, balanced, or altered in a way that should augment the flavor, acidity, aftertaste and body of the coffee as desired by the roaster.
The first stage is endothermic where the green beans are slowly dried to become a yellow color and where the beans begin to smell like toast or popcorn.
The second step, often called the first crack, occurs at approximately 205 °C (400 °F) in which the bean doubles in size, becomes a light brown color, and experiences a weight loss of approximately 5%. The corresponding Agtron number for this color is between 95-90 (Davids, 68-69).
In the next step the temperature rises from 205 °C to approximately 220 °C, the color changes from light brown to medium brown (Agtron # 60-50), and a weight loss of approximately 13% occurs (Davids, 68-69). The resulting chemical process is called pyrolysis and is characterized by a change in the chemical composition of the bean as well as a release of CO2.
The second step is followed by a short endothermic period which is followed by another exothermic step called the second crack. This second pyrolysis occurs between 225-230°C, and the roast color is defined as medium-dark brown (Agtron #50-45) (Davids, 68-69). The second pop is much quicker sounding and the beans take on an oily sheen. Espresso potential is maximized in roasting when you maximize the sweetness and aroma of the coffee while minimizing the bitterness and acidity. Most people focus on the latter and therefore roast extremely dark, yet without sweetness and aroma the espresso will never be palatable. This explains the unpopularity of straight espresso and the popularity of espresso based drinks where either milk or other flavors are used to replace the sweetness that was lost by roasting darkly.
From 170-200°C the sugars in coffee begin to caramelize. From tasting pure sugar versus its caramelized component it is evident that uncaramelized sugar is much sweeter. The dark color of coffee is directly related to the caramelization of the sucrose in coffee. Therefore, to maximize sweetness you want to minimize the carmelization of sucrose, yet you do not want to roast too lightly or bitter tasting compounds will not thermally degrade. Stop the roast somewhere between the end of the first crack and less than halfway through the second crack. Do not roast far into the second crack. We recommend a roasting chamber temperature somewhere between 205-215°C. Realizing the danger of the following suggestion we might recommend a color similar to the one below. Note: All monitors, computers, and internet browsers will display the color slightly different. This is only a recommendation to point out that this color is preferable to the almost black color you will frequently observe for espresso. To get a better idea of roasting colors order the Agtron roasting classification kit from the SCAA.
Coffee Blending
Coffee Blending is necessary for espresso since a single coffee origin will lack the complexity desired. It is important to remember that the advantage of espresso over other brewing methods is a result of the formation of the crema. Without the crema the espresso would be strong, thick coffee. The crema is an emulsified layer of tiny, smooth bubbles that trap aromatic compounds. This layer coats the tongue and these small bubbles break over time allowing espresso to be enjoyed long after it has been consumed. An aromatic coffee, therefore, is essential to a well prepared espresso blend.
The majority of the espresso blend is made up of a base of coffees from Brazil, the Dominican Republic, Mexico, Peru, Panama or any other origins that contribute a non-overbearing flavor while still contributing to the body and sweetness of the coffee. Small ratios of coffees from Colombia, Costa Rica, Guatemala, and Venezuela are used to add body, acidity, and flavor to a coffee blend. Since these coffees are often very acidic, they are used in small amounts.
To add complexity and brightness when blending espresso, Ethiopian Harrar, Kenyan, Yemen Mocha, Zimbabwe, and Zambian coffees are used. Ethiopian Harrar adds a powerful aroma of blueberries or raspberries while Kenya coffee adds a powerful brightness. To add richness and body when blending for espresso, coffee from the Asian Pacific, such as Sumatra, Sulawesi, Java, East Timor, New Guinea and Ethiopian Yirgacheffe are used. Yirgacheffe has a potent, flowerlike aroma.
Blending for Espresso Coffee
It is usually preferred to roast each coffee separately to its own individual peak and then blend coffee to create the most complexity.
Creating a good espresso blend is not as difficult as it may initially appear. Within a few hours you should have an acceptable espresso blend that will surpass commercial competitors for the simple reason that it is fresher. To perfect the espresso blend by altering the roast to achieve the perfect crema, flavor, acidity, body and aftertaste takes time and patience, but is a rewarding and educational experience. It is often difficult to balance the intense acidity of a shot of espresso which contains a brighter coffee which is used to contribute complexity and liveliness without roasting through the second pop. A successful espresso blend, therefore, should balance this acidity via creative mixing coffee rather than excessive roasting the beans. Do not roast your espresso past or even more than half way through the second pop. By not over roasting, you will preserve the delicate aroma and sugars in the coffee.
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