4.2.3 Cooling of roasted coffee
Once the coffee is roasted it needs to be cooled rapidly immed iately after being extracted from
the drum. The coffee should be brought to a temperature of 50°C in 3 minutes. A mechanical system with
strong aspiration system (using a vacuum cleaner achieves cooling of 1 kilo of coffee in less than 3
minutes. But the feasibility for ru ral areas is not satisfactory.
A manual cooling gives reasonable performances. The co ffee has to be spread on a large area to
maximize contact with ambient air. Cooling was carried out on a large piece of cartridge.
Creating artificial wind on the coffee accelerates sign ificantly the cooling in comparison to
letting it cooling by natural convection. For example in test 13, 1.5 kg was cooled down to 50°C in 7.5
min. 0.75 kg was cooled down in 4.5 min (test 15).
Improvement could be achieved using a stainle ss steel grid. Metal is a good material as heat can
be evacuated rapidly and the grid holes enable elimination of the remaining silver skins. Stainless steel
respects the food quality