Freeze-dried fruit is produced using a vacuum freeze-drying process. Drying food typically requires heating, so how can food be dried while frozen? Anyone who has studied physics knows that water has a three-phase curve. When frozen, a small amount of water molecules will directly escape from the ice and transform into water vapor. This transformation is called sublimation.
The vacuum freezing equipment first freezes the fruit to -30 to -40 degrees Celsius, filling the food with numerous tiny ice crystals. The air is then removed, lowering the air pressure. The water vapor generated by the sublimation of the ice crystals is also continuously extracted, causing the ice-air phase equilibrium to favor the formation of water vapor.
In this way, the ice crystals in the food continuously transform into water vapor at low temperatures. After dozens of hours, the food becomes dry.
Because the ice crystals transform directly into vapor, quietly leaving the food matrix without passing through the liquid phase, they leave many gaps within the food, resulting in a crunchy texture.
Because it requires both freezing and vacuuming, this process is very energy-intensive and more expensive than other dehydration methods, including sun drying, hot air drying, infrared drying, microwave drying, and low-temperature frying.
However, the investment pays off.
