Preserving Aroma Substances in a Better Way
The ground raw coffee is extracted: Extraction is the separation of the soluble components of coffee by means of water and pressure. The result is a liquid extract. The extraction itself occurs in a serially-connected, steel extraction columns in a counter-current-process. These columns are filled with freshly-ground coffee alternately whilst the extracted coffee is being separated. During the extraction process the water is pressed at a temperature of 170 °C (338 °F) to 190 °C (374 °F) through the different columns, until the liquid coffee extract is cooled down at a temperature of 40 °C (104 °F) to 80 °C (176 °F). The extracted coffee is then filled into silos in a concentrated form.
Deep-freezing and drying of the liquid coffee: The liquid coffee is frozen to –20 °C (–4 °F) until it becomes a thicker consistency. Ice crystals are formed and the coffee looks like soft ice cream. Only in this consistency can it be sprayed onto a steel-frozen-conveyor-belt and sent into the freezing chamber. The coffee is frozen to –50 °C (–58 °F) turning into a brown ice block with a width of 1 m and a thickness of approx. 1 cm. By means of shock-freezing little ice crystals are formed, which do not destroy the plant cell walls. Then the coffee is ground and filtered.
In this freezing chamber the first Kammerer-charging-sluices can be found. These consist of two absolutely vacuum-tight shut-off-valves of the GPT-type: the upper valve is a product-tight-valve and the lower one is a vacuum-tight-valve. Both valves are linked to one another by a pipe section which lock together. The sealing of the GPT-type occurs by means of O-rings. The frozen coffee is collected on the upper slide gate valve avoiding the entry of possible coffee particles and coffee dust from getting into the sealing system of the lower vacuum-tight slide gate valve.
Should a specified portion have been collected on the upper slide gate valve it is then opened, allowing the frozen coffee to drop down into the pipe section and onto the lower vacuum-tight-valve. The upper product-valve is closed, the pipe section is placed under vacuum and the lower slide gate valve is opened. The product drops into an agitator vessel, in which the frozen coffee is mixed again, after which it goes through the second Kammerer-sluice-system leaving the freezing chamber to get into the vacuum disc dryer.