Freeze-driers have three major parts: · A chamber where the product is placed. It is frozen either before entering this chamber or inside of it. · A cold trap (condenser) to capture most of the removed solvent or water. It is a key element as its efficiency will greatly impact the required vacuum capacity and the cost of the system. · A vacuum unit A pre-frozen product is placed in an air-tight drying chamber. A vacuum pump reduces the air pressure inside the chamber until a pressure of 1 to 0.5 mbar is reached. Under vacuum, the evaporation process of the frozen water already starts at -50 to -40° Celsius. The water vapor is then suctioned out of the drying chamber by the vacuum pump and directed into a downstream condenser. In this so-called ice trap, cooled to at least -70° Celsius, the water vapor deposits on a cooling coil as ice. Most of the moisture is removed from the product in this primary drying phase. In the case of many foodstuffs, primary drying is followed by secondary drying. This process takes away more residual moisture by lowering the vacuum level to 0.01 mbar or below while raising the temperature above the freezing point. The drying chamber is then ventilated to atmospheric pressure. For ventilation, dry air or an inert gas is used, so that the dried product cannot absorb moisture from the ambient air. Finally, the dried product, with a water content of one to four percent, is removed for further processing.