7 Things To Know About The Freeze-dried Food Craze | Mother Jones
Freeze-drying food
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," in which any 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 precursor to beef jerky (charqui), placing food on high-elevation stone platforms to freeze overnight and then dry in the sun.