Description
Dehydration removes free water by heat or solar exposure, while freeze‑drying sublimates ice under vacuum to preserve structure and nutrients.
Technical
In hot‑air dehydration, water evaporates as vapor driven by temperature and reduced humidity, lowering water activity (a_w) below 0.6 to inhibit bacterial growth. Freeze‑drying first freezes the product at –40 °C to form small ice crystals, then primary drying sublimates ~90 % of water at –30 to –20 °C under <0.1 mbar, and secondary drying removes bound water at 20–30 °C, achieving a_w < 0.1.
Science
Primary Reaction
Evaporation (hot‑air) or sublimation (freeze‑drying)
Sensory Profile
Aroma ()
drysmokyumamicrispearthynuttycaramelized
Origin & History
Civilization