![]() Primary drying: Also known as proper freeze-drying, this is the sublimation step in which frozen free water is removed.Freezing: The product is often frozen under atmospheric pressure.The freeze-drying process can be divided into three steps ( 1, 3, 4): In fact, this is the primary difference between freeze- and vacuum-drying - and the most challenging step ( 1). In the freeze-drying process, all free water and some bound water must be removed, and free water must remain frozen at all times. While free water freezes, bound water doesn’t ( 1). Raw foods are comprised of about 80%–95% water, which can be divided into “free” and “bound” water. ![]() freezing inhibits chemical and microbiological processes, which significantly delays the product’s deterioration (thereby extending its shelf life).it operates at low temperatures, which contributes to preserving a product’s nutritional value, taste, appearance, and heat-sensitive compounds.This means that the product’s water content transitions from a solid to a gaseous state - or from ice to vapor - without going through the liquid state ( 1).įreeze-drying is considered a high quality dehydration method for a couple of reasons, including ( 1, 2): Freeze-drying or lyophilization is a dehydration technique based on the sublimation of water in a product ( 1, 2).
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