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Updated: May 17, 2026

Process Development for the Spray-Drying of Probiotic Bacteria and Evaluation of the Product Quality
Published on: April 7, 2023
Mechanisms of water migration and their impact on probiotic stability during freeze-drying: A comprehensive review
Hui Yao1, Shufeng He1, Tchouli Noufeu1
1State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-products, Ningbo University, Ningbo, China; Key Laboratory for Food Microbiology and Nutrition of Zhejiang Province, College of Food Science and Engineering, Ningbo University, Ningbo, 315211, China; Zhejiang-Malaysia Joint Research Laboratory for Agricultural Product Processing and Nutrition, Ningbo University, Ningbo, China.
Abstract:
Vacuum freeze-drying is a critical technology for extending the shelf life of probiotics while preserving their functional viability. However, during processing, water migration and ice crystal formation can lead to substantial cellular damage and reduced viability. This review aims to address the following key scientific questions: (i) how water migration evolves across different freeze-drying stages, (ii) how these mechanisms affect probiotic stability, and (iii) how these processes can be controlled through formulation and process design. We systematically examine water migration mechanisms during freezing, primary drying (sublimation), and secondary drying (desorption), and their effects on probiotic survival. Each stage involves distinct physical transformations of water, which influence ice crystal growth, membrane integrity, and the development of a glassy matrix. These processes are governed by interactions between intrinsic factors (e.g., enzymes, proteins, lipids, and exopolysaccharides) and extrinsic factors (e.g., medium composition, cryoprotectants, and process parameters), which collectively regulate water behavior and phase transitions. Recent advances in characterization techniques-including differential scanning calorimetry, nuclear magnetic resonance, Raman spectroscopy, and process analytical technologies-now enable multi-scale monitoring of water mobility and state changes. The review highlights that optimizing process control, developing hybrid freeze-drying strategies, innovating cryoprotectant formulations, and implementing multiscale modeling of water kinetics are essential for precise moisture management during probiotic freeze-drying. These strategies are key to improving probiotic survival and maintaining biological activity. In conclusion, this mechanistic understanding provides a scientific basis for the rational design of freeze-drying protocols and the development of next-generation probiotic products with enhanced stability and functionality.
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