GefrierTrocknungsverfahren

GefrierTrocknungsverfahren, commonly referred to as freeze-drying or lyophilisation, is a dehydration process that removes water from a product by freezing it and subsequently sublimating the ice under low pressure. The technique is widely employed in the food, pharmaceutical, and biotechnological industries to preserve heat‑sensitive materials while maintaining their structural integrity, flavour, and bioactivity.

The process consists of three main stages. Firstly, the product is rapidly frozen to lock in its molecular structure and prevent the formation of large ice crystals. Secondly, the frozen material is subjected to a vacuum environment where the temperature is gradually lowered; this creates a pressure range that allows frozen water to transition directly from solid to vapor (sublimation) without passing through the liquid phase. Finally, the sublimated water vapour is removed, leaving a dry product with a porous matrix that can be rehydrated quickly.

Key advantages include reduced oxidation, high product stability, and lower energy consumption compared with conventional drying. However, freeze-drying can be costly due to the need for specialised refrigeration and vacuum equipment, and it is not suitable for substances that are highly hygroscopic or prone to sublimation under the operating conditions.

Applications span from the preservation of fruits, cheeses, and medicinal compounds to the preparation of powdered vaccines and biologically active proteins. Continued research focuses on scaling the process, improving throughput, and integrating advanced sensors to optimise the freeze-drying cycle.