Freeze Dryers for Coffee

Freeze drying takes place from a frozen product under vacuum below the “triple point” = 4.6 torr (6.2 mbar). Below the triple point water will only be present in two phases: ice and vapour. By adding energy to the ice, it will sublimate directly into the vapour phase without passing the liquid water phase.

Due to the high total solids in the coffee concentrate it is, however, necessary to operate at a much lower pressure (higher vacuum) than at the "triple point'. The low pressure (high vacuum) prevailing in the freeze drying chamber/cabinet means that the water vapour has an enormous volume. (1 l water on vapour form at 0.4 mbar = 2800 m³). To maintain the vacuum the vapours are therefore condensed as ice on the surface of tubular cooling/condensing vapour traps.

The vapour traps are placed inside the freeze drying chamber. One vapor trap is in operating while the other is automatically separated from the tunnel and de-iced. Prior to the actual freeze drying process the concentrated coffee extract must be pretreated in a special way to obtain the desired final quality of the coffee powder.

The pretreatment consists of:  

• Cooling, pre-freezing and foaming 
• Freezing with pre-breaking 
• Granulation (milling) and sieving

These processes determine the final colour, bulk density, solubility and mechanical stability of the coffee powder. It is therefore very important that this technology is mastered and at the same time flexible enough to change final product characteristic to meet that of the market.

CONRAD™ freeze dryer

Freeze drying plants from GEA Niro
GEA Niro offers two types of freeze drying plants for coffee:

The RAY™ freeze dryer is a batch process and is used for smaller capacities. The filled trays with granulated frozen flakes are manually loaded on trolleys and then placed in the RAY™ cabinet. The actual freeze drying takes place automatically.

The CONRAD™ (Continuous Radiation) freeze dryer is a continuous freeze drying cabinet and is used for larger capacities. Here the filled trays with granulated frozen flakes leave the cold store (-40^oC) automatically and are loaded into the CONRAD™ freeze drying cabinet via a valve system. During the freeze drying, the trays are automatically moved to the discharge point, where they are emptied and returned to the cold store.