Freeze-drying is a key unit operation widely used in both the pharmaceutical and agro-food industries. In the pharmaceutical field, it plays a crucial role in the stabilization of sensitive biomolecules, vaccines, and injectable products. In the food industry, it is employed to preserve nutritional and organoleptic properties of products such as coffee, fruits, or probiotics, by ensuring extended shelf-life without the need for chemical preservatives.
The process itself involves three main stages: (1) freezing, during which water in the product crystallizes; (2) primary drying (sublimation), where ice is removed under low pressure representing the most energy- and time-intensive step; and (3) secondary drying (desorption), where residual bound water is removed to achieve the desired final moisture content. Freeze-drying remains a complex process, strongly influenced by operating conditions such as shelf temperature, chamber pressure, and product formulation.