Overcoming common freeze drying challenges

In this paper, GEA specialists discuss how freeze drying professionals can overcome common freeze drying challenges by altering tray shape, changing product geometry, and creating more uniform heat distribution. Using test data from freeze-dried raspberries, black currents, mangos, carrots, and chicken, GEA specialists provide further recommendations for optimizing capacity, maintaining quality, and creating a productive and profitable freeze drying process.

Author: Troels Bjerregaard Pedersen, Process Specialist

1. The benefits and challenges of freeze drying

   
   Freeze drying is an effective way to preserve the shape, color, taste, and nutrients of many types of food and beverages while vastly increasing their shelf life. 
   
   The process involves drying a frozen product in a vacuum below the triple point, allowing for a sublimation process that direct converts ice into vapor without an intermediate liquid state. With freeze drying, only vapors are transported in the product, which contrasts to conventional drying methods taking place above the triple point.
   
   Freeze drying can be divided into internal processes inside the product and external processes outside of the product.
   
   Internal processes include freezing the product, sublimation, heat transfer within the product and drying hygroscopic-bound water (secondary drying). 
   External processes cover heat transfer to the product and handling released vapors.
   Freezing can happen in the freeze dryer or as a separate process outside the freeze dryer, which is the standard in GEA...