What is the technology behind freeze dried food

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MANY foods are freeze-dried today. The staple of astronauts, soldiers, and hikers, freeze dried foods are considered a good way of storing food (and some make great healthy snacks!).

However, it might be surprising to note that the technique of freeze-drying is quite old. Freeze-drying is a three-step process that begins with freezing. Next the food is placed in a vacuum chamber under low heat. The frozen water crystals evaporate directly from ice to water vapor in a process called sublimation.

The food then undergoes “secondary drying,” where remaining water molecules are removed under slightly higher temperatures. The food is nitrogen-sealed for storage to prevent contamination from water or oxygen.

As far back as 1200 A.D., the Incas freeze-dried potatoes (chuño) and a pre-cursor to beef jerky (charqui), placing food on high-elevation stone platforms to freeze overnight and then dry in the sun.

However, freeze-drying is one of the most energy-intensive ways to preserve food, according to R. Paul Singh, a University of California-Davis food science and technology professor – 1.2 times more energy than canning, and 1.7 times more energy than freezing is used. Nevertheless, freeze dried food is pretty healthy and also quite tasty, judging from the excellent response of people towards it.