The Coffee Process – From Crop to Cup
27.7.04
Be ready for a great journey. In this chapter you’ll learn how coffee is prepared, from when it is plucked from the bush to when its packed and ready for you to buy.
Harvesting
Harvesting coffee can be done manually or by machine. The most crude method is called stripping. Used in Brazil and Africa, everything is stripped from the branches by hand, which means that not only are the ripe coffee berries removed but also immature berries, leaves and twigs. This method guarantees a high yield and is fast and easy to do. But the coffee produced is very poor with under-ripe and over-ripe fruits often tainting the final product.
Intermediate methods are better than stripping. The coffee bushes are either combed with a special tool that only removes ripe fruit or shaken with a special machine to make the fruit fall off the bush. However, when some leaves and twigs are removed the quality of the beans is by no means guaranteed.
The best method by far is picking, but this is also time consuming and delicate. Workers pluck ripe berries by hand, repeating the process up to 7 times a year as more fruit gradually ripens. This method is used in Central America and gives the best results by far.
Processing
After the coffee is harvested the bean must be extracted from its fleshy berry coating. There are two methods of obtaining the green bean, dry processing and wet processing. Each gives different final results.
In the wet processing method the berries are put to soak in water, only hours after harvesting. When the berries are softened the pulp around the beans is removed by a machine with special rotating disks. With most of the pulp gone the beans are again placed in water, healthy beans sink but diseased ones float and are skimmed off. The last remnants of pulp are removed by 12 to 48 hours of constant stirring after fermenting. Then the beans are washed again and dried, either mechanically or in the sun. The final result is smooth and mild, an excellent coffee.
However this is offset by the cost and water consumption associated with the method. For this reason its use is mainly restricted to high grade arabicas and asian robustas.
Dry processing is the original and cheaper method and is used for most robustas and some low grade Arabicas. The harvested berries are spread out in the sun to dry. They are turned regularly to prevent the formation of mould and ensure even drying. After 15 days the pulp has dried leaving just a shell around the green bean which is easily removed. The resulting coffee is full bodied but lacks true flavour.
After the beans have been processed there is another optional step called polishing. The beans will still have a thin silvery skin if they were dry processed. This can be removed to reveal the smooth green bean. However this step is largely cosmetic and makes little difference to the final product.
Grading and Sorting
After being processed, either wet or dry, and polished, green coffee beans must be carefully sorted and graded to ensure a clean high quality product. Today most of the sorting process is fully mechanized and comprises seven stages. First, the beans are vacuumed with a machine called a catador that removes any dirt and debris left after drying and hulling. Secondly, a magnet removes stray pieces of metal such as nails and wire.
The beans are then placed on a series of wire screens to separate coffee beans of different sizes. The largest size being 18 and the smallest 8. This is important as the larger beans produce better quality coffee. Next air is blown over the beans to remove any last bits of dirt and dust. Then a colour sensing machine called a colorimeter detects any under-ripe beans. It does this by sorting out the paler ones.
A similar device that uses UV light detects any rotten beans that are known as ‘stinkers’. Any beans that don’t pass the light tests are shot away by a quick burst of compressed air. And lastly the beans are sometimes examined by hand to remove any stray defective beans. The beans are now ready for packing and exporting, the next instalment in our series on coffee processing. With a process as complex as this its no wonder the coffee we drink today is of such high quality.
Exporting and Storage
The sorted green beans are stored for 2 months up to five years. They’re packed either in standard 60kg hessian sacks or otherwise in giant containers. Storage in sacks is more expensive, but if some beans begin to ferment only one sack is contaminated rather than an entire container. Even storage poses risks to good coffee. Excessive heat and humidity over long periods spoil the flavour.
Sea air at harbours can give coffee a salty taste, when this happens it is described as Rioed because Brazilian coffee is often affected in this way. Coffee beans can even have a banana flavour! If transported in banana boats the strong odour infuses its way into the beans. The coffee is then transported all over the world. All coffee producing nations, with the exception of Brazil, export the vast majority of the annual crop.
Roasting
The most important step in coffee production. Without roasting coffee would be a weak, excessively bitter infusion instead of the rich full flavoured brew we all know and love. Like most of the other steps of coffee production there is a traditional superior method that’s expensive and a modern method that’s cheaper but produces a lower quality product.
The traditional method guarantees quality and takes 15 to 23 minutes depending on how dark a roast is desired. The green beans are fed into a rotating drum and heated by a hot air generator. In the first ten minutes from when the beans reach 160 degrees C. The proteins and sugars react to form aromatic and coloured substances, this change is known as Maillard reactions. Some of these products break down as the beans become hotter and darker which is known as Strecker degradation and produces the roasted flavours. After a further ten minutes the water content and sugars disappear. The beans lose 20% of their weight but gain in volume by 60%.
Gas released by the heat creates a crackling noise and master roasters can detect the degree of roast by this sound. The roasted beans are dropped onto a grille and quickly cooled by unheated air because otherwise they may actually ignite.
Industrial methods are quicker but produce a lower quality bean. In fluidised bed roasting the beans are blown around a cone shaped chamber by air currents heated to 800 degrees C for 4 to 10 minutes. This method doesn’t allow full flavour development but is sufficient for standard grade coffee. The second method is known as flash roasting and only requires 90 seconds at a constant temperature of 800 degrees C.
After roasting the beans are placed in silos for 1 or 2 days to allow excess gases to bleed off. Then all that is left is for the beans to be either packaged whole, or pre-ground and ready to make your favourite type of coffee.
Final Step – Brewing Espresso!
There are many ways to prepare a cup of hot delicious coffee. The earliest kind of coffee maker was the Turkish coffee pot which was simply a tall thin saucepan with a spout for pouring. Finely ground coffee was boiled several times becoming strong with good body and flavour. However before drinking, the grounds had to be allowed to settle and would form a layer at the bottom of the cup.
The drip pot was invented in France in 1800. It consists of a double chambered china pot, with the chambers separated by a perforated section. Water was poured in top, trickled over the coffee grounds in top leaving the bottom full of coffee which was poured out through a spout. The filter let some grounds through and was very difficult to clean properly.
The Moka Express was invented in the 1950’s by the Italian company Bialetti. Water is boiled in the bottom chamber creating steam that forces water up over the grounds in the centre and into the chamber on top. The coffee it produces is said to be overextracted due to the very high temperature it is brewed at. And if the Moka is made of aluminium this tends to taint the coffee’s taste. Whatever the experts say, many people do like the Moka Express and it still sells strongly today.
The cafetierie or bodum is the plunger coffee maker that can be found in the home of almost all coffee lovers. Coarsely ground coffee is left to infuse for 3 minutes, the plunger then pushes the filter down, compressing the grounds at the bottom. When used properly this cheap, easy to use device produces excellent coffee.
The electric coffee filter is another common home and office option for coffee making. Water drips into the centre of the coffee and fails to contact all of the grounds. As a result it makes mild, bland coffee with a slightly acidic flavour. Its weaknesses are magnified by the fact that the coffee is then often allowed to rest for hours on a heating plate producing an unpleasant acrid flavour.
But the best method of all in terms of finished product is the modern espresso machine.
Harvesting
Harvesting coffee can be done manually or by machine. The most crude method is called stripping. Used in Brazil and Africa, everything is stripped from the branches by hand, which means that not only are the ripe coffee berries removed but also immature berries, leaves and twigs. This method guarantees a high yield and is fast and easy to do. But the coffee produced is very poor with under-ripe and over-ripe fruits often tainting the final product.
Intermediate methods are better than stripping. The coffee bushes are either combed with a special tool that only removes ripe fruit or shaken with a special machine to make the fruit fall off the bush. However, when some leaves and twigs are removed the quality of the beans is by no means guaranteed.
The best method by far is picking, but this is also time consuming and delicate. Workers pluck ripe berries by hand, repeating the process up to 7 times a year as more fruit gradually ripens. This method is used in Central America and gives the best results by far.
Processing
After the coffee is harvested the bean must be extracted from its fleshy berry coating. There are two methods of obtaining the green bean, dry processing and wet processing. Each gives different final results.
In the wet processing method the berries are put to soak in water, only hours after harvesting. When the berries are softened the pulp around the beans is removed by a machine with special rotating disks. With most of the pulp gone the beans are again placed in water, healthy beans sink but diseased ones float and are skimmed off. The last remnants of pulp are removed by 12 to 48 hours of constant stirring after fermenting. Then the beans are washed again and dried, either mechanically or in the sun. The final result is smooth and mild, an excellent coffee.
However this is offset by the cost and water consumption associated with the method. For this reason its use is mainly restricted to high grade arabicas and asian robustas.
Dry processing is the original and cheaper method and is used for most robustas and some low grade Arabicas. The harvested berries are spread out in the sun to dry. They are turned regularly to prevent the formation of mould and ensure even drying. After 15 days the pulp has dried leaving just a shell around the green bean which is easily removed. The resulting coffee is full bodied but lacks true flavour.
After the beans have been processed there is another optional step called polishing. The beans will still have a thin silvery skin if they were dry processed. This can be removed to reveal the smooth green bean. However this step is largely cosmetic and makes little difference to the final product.
Grading and Sorting
After being processed, either wet or dry, and polished, green coffee beans must be carefully sorted and graded to ensure a clean high quality product. Today most of the sorting process is fully mechanized and comprises seven stages. First, the beans are vacuumed with a machine called a catador that removes any dirt and debris left after drying and hulling. Secondly, a magnet removes stray pieces of metal such as nails and wire.
The beans are then placed on a series of wire screens to separate coffee beans of different sizes. The largest size being 18 and the smallest 8. This is important as the larger beans produce better quality coffee. Next air is blown over the beans to remove any last bits of dirt and dust. Then a colour sensing machine called a colorimeter detects any under-ripe beans. It does this by sorting out the paler ones.
A similar device that uses UV light detects any rotten beans that are known as ‘stinkers’. Any beans that don’t pass the light tests are shot away by a quick burst of compressed air. And lastly the beans are sometimes examined by hand to remove any stray defective beans. The beans are now ready for packing and exporting, the next instalment in our series on coffee processing. With a process as complex as this its no wonder the coffee we drink today is of such high quality.
Exporting and Storage
The sorted green beans are stored for 2 months up to five years. They’re packed either in standard 60kg hessian sacks or otherwise in giant containers. Storage in sacks is more expensive, but if some beans begin to ferment only one sack is contaminated rather than an entire container. Even storage poses risks to good coffee. Excessive heat and humidity over long periods spoil the flavour.
Sea air at harbours can give coffee a salty taste, when this happens it is described as Rioed because Brazilian coffee is often affected in this way. Coffee beans can even have a banana flavour! If transported in banana boats the strong odour infuses its way into the beans. The coffee is then transported all over the world. All coffee producing nations, with the exception of Brazil, export the vast majority of the annual crop.
Roasting
The most important step in coffee production. Without roasting coffee would be a weak, excessively bitter infusion instead of the rich full flavoured brew we all know and love. Like most of the other steps of coffee production there is a traditional superior method that’s expensive and a modern method that’s cheaper but produces a lower quality product.
The traditional method guarantees quality and takes 15 to 23 minutes depending on how dark a roast is desired. The green beans are fed into a rotating drum and heated by a hot air generator. In the first ten minutes from when the beans reach 160 degrees C. The proteins and sugars react to form aromatic and coloured substances, this change is known as Maillard reactions. Some of these products break down as the beans become hotter and darker which is known as Strecker degradation and produces the roasted flavours. After a further ten minutes the water content and sugars disappear. The beans lose 20% of their weight but gain in volume by 60%.
Gas released by the heat creates a crackling noise and master roasters can detect the degree of roast by this sound. The roasted beans are dropped onto a grille and quickly cooled by unheated air because otherwise they may actually ignite.
Industrial methods are quicker but produce a lower quality bean. In fluidised bed roasting the beans are blown around a cone shaped chamber by air currents heated to 800 degrees C for 4 to 10 minutes. This method doesn’t allow full flavour development but is sufficient for standard grade coffee. The second method is known as flash roasting and only requires 90 seconds at a constant temperature of 800 degrees C.
After roasting the beans are placed in silos for 1 or 2 days to allow excess gases to bleed off. Then all that is left is for the beans to be either packaged whole, or pre-ground and ready to make your favourite type of coffee.
Final Step – Brewing Espresso!
There are many ways to prepare a cup of hot delicious coffee. The earliest kind of coffee maker was the Turkish coffee pot which was simply a tall thin saucepan with a spout for pouring. Finely ground coffee was boiled several times becoming strong with good body and flavour. However before drinking, the grounds had to be allowed to settle and would form a layer at the bottom of the cup.
The drip pot was invented in France in 1800. It consists of a double chambered china pot, with the chambers separated by a perforated section. Water was poured in top, trickled over the coffee grounds in top leaving the bottom full of coffee which was poured out through a spout. The filter let some grounds through and was very difficult to clean properly.
The Moka Express was invented in the 1950’s by the Italian company Bialetti. Water is boiled in the bottom chamber creating steam that forces water up over the grounds in the centre and into the chamber on top. The coffee it produces is said to be overextracted due to the very high temperature it is brewed at. And if the Moka is made of aluminium this tends to taint the coffee’s taste. Whatever the experts say, many people do like the Moka Express and it still sells strongly today.
The cafetierie or bodum is the plunger coffee maker that can be found in the home of almost all coffee lovers. Coarsely ground coffee is left to infuse for 3 minutes, the plunger then pushes the filter down, compressing the grounds at the bottom. When used properly this cheap, easy to use device produces excellent coffee.
The electric coffee filter is another common home and office option for coffee making. Water drips into the centre of the coffee and fails to contact all of the grounds. As a result it makes mild, bland coffee with a slightly acidic flavour. Its weaknesses are magnified by the fact that the coffee is then often allowed to rest for hours on a heating plate producing an unpleasant acrid flavour.
But the best method of all in terms of finished product is the modern espresso machine.
posted by Wayne Fowler | 10:14 PM
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