Freeze Drying Process Overview

The Freeze Drying Process

Freeze drying (lyophilization) is a dehydration process that operates in three stages:

1. Freezing: The product is frozen to below its eutectic point, typically -30°C to -50°C. The freezing rate affects ice crystal size, which impacts product quality.
2. Primary Drying (Sublimation): Under deep vacuum (≤30 Pa), heat is applied to the product to drive sublimation. Ice transitions directly to vapor without passing through the liquid phase. This stage removes 90-95% of the water.
3. Secondary Drying (Desorption): The temperature is raised to remove bound water molecules through desorption. This stage brings the final moisture content to 1-4%.

The total process can take 12-48 hours depending on product thickness, composition, and equipment specifications.