Una variedad de caramelos liofilizados, incluidos caramelos arcoíris liofilizados, malvaviscos liofilizados, gomitas liofilizadas, etc.
Jan 24, 2024
The future of freeze drying
Freeze drying (lyophilization) has been used industrially for decades to preserve foodstuffs and biological materials, but traditional tray-type freeze dryers are slow and labor-intensive. A new ‘Active Freeze Drying’ process promises to eliminate these drawbacks.
The future of freeze drying
The history of freeze drying goes back to the ancient Inca’s, who preserved potatoes and other vegetables simply by exposing them to the air. Low winter temperatures turned the water in the food to ice, which then evaporated in the very dry mountain air. In the 1930s, industrial freeze drying was developed as a way to preserve surplus coffee in countries such as Brazil. Nescafé and other famous brand names were founded at this time, and instant coffee is now the best-known freeze-dried product. During the Second World War, freeze drying was also used for wartime medical supplies such as penicillin and blood plasma. In the following decades the use of freeze drying expanded to the point where today the technology is used in the production of around 400 different foodstuffs and many pharmaceuticals.
Problems with traditional method
Ever since the 1930s, industrial freeze drying has depended on a single type of equipment: the tray-type freeze dryer. In a tray freeze dryer, the material to be dried is placed on open trays and supported on shelves equipped with cooling and heating systems. The trays are arranged within a chamber that is connected to a vacuum pump.
First, the material is frozen at atmospheric pressure by lowering the temperature of the shelves. The drying chamber is then evacuated to a pressure typically in the range 0.01-1 mbar. Gentle heat applied to the shelves causes ice in the product to evaporate without passing through the liquid phase (sublimate). The deep vacuum allows this to take place at the temperature of -20C or even lower. If necessary, for instance where organic solvents are used, solvent is recovered from the vacuum pump exhaust by a low-temperature condenser.
Despite successful operation over many decades, tray freeze dryers have three significant disadvantages. First, loading and unloading is labor-intensive, especially since large units may contain several hundred trays. Second, the freeze-dried cake removed from the trays often requires grinding to convert it to a free-flowing granular product. Third, the formation of a ‘skin’ of dried product on the surface of the tray hinders the passage of vapor, making this method of freeze drying very slow.
