US Patent 11744257 Freeze-drying methods including vacuum freezing

Various implementations of a freeze-drying method are described where the material is cooled by reducing the pressure in a chamber to evaporate and/or sublimate water in the material. In one implementation, the material is dried in the chamber by sublimating ice in the material to water vapor. In another implementation, the freeze-drying method includes actively cooling the chamber. In another implementation, at least a portion of the water vapor is deposited on an actively cooled interior surface of the chamber. In another implementation, the freeze-drying method includes cooling the material to −25° F. or below. In another implementation, the material is cooled at approximately ambient pressure to 30° F. or below and then cooled by reducing the pressure in the chamber.