Grandsaugreen unique freeze drying process preserves all essential aspects of the coffee extract, retaining the quality parameters with regard to product colour, bulk density and solubility. Further, the carefully designed system ensures the right granule size and size distribution.
At Grandsaugreen we use carefully selected Arabica and Robusta coffee beans in varying combinations to produce a unique blend for complete satisfaction of the person consuming the coffee, and for an aroma that continues long after the coffee has been consumed.
The freeze-drying method preserves the ‘coffee flavour’ to a great extent. In this process, first, the coffee is allowed to sit so the water evaporates naturally, leaving a concentrated coffee solution. This concentrate is then frozen to around – 40 Degree Celsius. The remaining water freezes into ice crystals. Sublimation (a natural process similar to evaporation) is used to remove the ice, leaving behind dry grains of coffee.
In this process, agglomerated wet coffee granules are frozen. This is a very important stage. Freezing too fast leads to large ice crystals and a very porous product and can also affect the colour of the coffee granules. Thereafter, frozen coffee is placed in the drying chamber, in metal trays. A vacuum is created within the drying chamber. The strength of the vacuum is critical to the speed of the drying and ultimately, to quality of the product. Great care must be taken to produce a vacuum of suitable strength.
Thereafter, the drying chamber is warmed, most commonly, by radiation. However, conduction is used in some plants and convection has been proposed in some small pilot plants. A possible problem with convection is uneven drying rates, within the chamber, which would give an inferior product.
Condensation – The previously frozen water in the coffee granules expands to 107 of its volume, The removal of this water vapour from the chamber is vitally important, making the condenser the most critical and expensive components in a freeze drying plant.
The freeze dried granules are removed from the chamber and packaged.