FREEZE DRYING
Food preservation is one of the most important technologies that exists. Whether it is canning, refrigerating, or freezing, we have come to depend on our ability to preserve foods. Freeze drying is one of the most effective methods of food preservation because it allows food to keep for years while minimally affecting its structure.
Freeze drying food is removing the water from it while leaveing the structure and composition. Removing the water keeps the food from spoiling because microorganisms need water to survive. It also significantly reduces the weight of the food. Astronauts take freeze dried food on space missions because of how long they last and how little space is needed to store them.
Just evaporating the water out of food will change the composition of the material and will not completely rid of the water. For this reason freeze drying is used sometimes instead. In the freeze drying process, the water goes from the frozen solid state to the gas phase without ever becoming liquid by lowering the pressure and raising the temperature (see graph).
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Is how this works is food is placed in a chamber and compressors are used to lower the temperature and freeze it. Then, a vacuum removes air, lowering the pressure below 0.06 ATM. The temperature inside the chamber is barely heated and the frozen water turns directly into vapor and exits the chamber where it condenses onto the refireration coils. This process takes a very long time so not to disturb the original structure of the food.
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FUN FREEZE DRIED FACT: Conscious about the environmental impact associated with cremation and embalming fluids, the Swedish company Promessa Organic has come up with the solution of freeze drying the dead.