Freeze-dried cake structural and physical heterogeneity in relation to freeze-drying cycle parameters

Area of Science:

• Pharmaceutical Science
• Materials Science

Background:

• Freeze-drying is crucial for stable protein manufacturing.
• Understanding the link between freeze-drying parameters and cake properties is vital for product quality.

Purpose of the Study:

• To investigate how freezing conditions affect the material properties of freeze-dried cakes.
• To examine these effects in both placebo and protein-containing formulations.
• To assess the role of annealing in mitigating freezing-induced heterogeneities.

Main Methods:

• Drying placebo and protein formulations using slow, fast, and fast cooling with annealing.
• Analyzing cake appearance, pore size distribution, and thermal events.
• Characterizing the crystalline phases, specifically mannitol polymorphs.

Main Results:

• Different freezing rates led to heterogeneous cake structures, varying pore sizes, and structural water release.
• Annealing enhanced crystallinity and eliminated material inhomogeneities across the cake.
• The crystalline phase was primarily composed of delta-mannitol and mannitol hemihydrate (MHH), influenced by protein presence and freezing parameters.

Conclusions:

• Freezing conditions significantly influence freeze-dried cake structure and material properties.
• Annealing is effective in improving cake uniformity and crystallinity.
• Controlling freezing parameters and understanding mannitol crystallization are essential for optimizing freeze-dried protein products.