Both the wine and coffee industry are based on the quality of its aromatic components. A bad vintage or a poorly designed industrial process can affect the image and development of the company.
The extraction of aromatic components of coffee beans is the soul of a good cup of coffee.
There are endless methods of brewing coffee at home. All of them propose to extract the precious aroma of roasted coffee beans: espresso machine, hand held espresso, stovetop espresso, aeropress, French press, coffee bag, vacuum pot or the percolator are some of them.
They are based on the same principle, the extraction of aromas with water through heat and pressure. Actually, the word espresso recalls "pressure" and is simply a method of distilling brewing coffee by forcing a small amount of nearly boiling water under pressure through finely ground coffee beans.
The objective is to extract the greatest amount of aromas from roasted coffee beans without affecting the quality of the product because it would produce bitter flavours.
At home you have plenty of options such as those described above, but today I am going to focus on the methods that the industry has to extract these delicate compounds.
Instant or soluble coffee
This method of industrial production intends to extract the aromatic compounds of coffee in large quantities, pack them and offer them to the consumer so, just adding water will reconstitute the coffee and a good quality is obtained.
Mainly there are 2 methods of extraction but they have a common stage: after the coffee beans have been roasted and ground in powder the aroma and flavours are extracted with hot water.
Finally, the extract is dried and, here is when the process of instant coffee can be made in two methods:
The extract is sprayed into a stream of hot air at the top of a tall cylindrical tower. As the droplets fall, they lose water by evaporation, becoming a fine powder by the time they reach the bottom. This powder may then be converted into granules adding a bit of water to facilitate dissolution. The quality of the flavour is preserved thank to the very fast drying occurring during this process but some aromas are lost during the evaporation process due to the high temperatures.
The coffee extract is frozen to about -40°C and cut into small granules. The frozen granules are then dried at low temperature and under vacuum, this process force the ice to vaporise (actually it is a sublimation), keeping intact the characteristics of aroma and flavour due to the very low temperatures and gentle drying conditions. The sublimation removes just the water but does not affect the aroma because the low temperatures doesn’t damage the aromatic molecules.
Spray-drying (left) , Freeze dried coffee (centre) and sprayed coffee (right)