The strategies to improve the survival of spray-dried probiotics: A comprehensive review

Spray-drying is regarded as a promising alternative to freeze-drying for probiotic powder production. However, maintaining probiotic viability remains a significant challenge. This review provides a comprehensive review of strategies to improve the survival of spray-dried probiotics, covering physical mixing of probiotics with protective substances, encapsulation techniques prior to spray-drying, optimization of spray-drying parameters, novel drying technologies, and probiotic strain pretreatments. The results showed that the survival of spray-dried probiotics can be enhanced through physical mixing with protective substances such as proteins, polysaccharides, oligosaccharides, small-molecule sugars, polymers, oils, and their combinations, which offer synergistic protective effects. Encapsulation before spray-drying, including complex coacervates and emulsions, further improves probiotic viability. Key spray-drying parameters-such as inlet temperature, feed rate, compressed air pressure, and material concentration-also significantly influence survival outcomes. Electrospraying, as a novel instrument development strategy, is discussed in terms of its methodology, advantages/limitations, influencing factors, and comparison with conventional freeze-drying and spray-drying. Strain pretreatments, such as heat pre-treatment and dormancy induction, are also highlighted as effective approaches to enhance probiotic stability. The industrial feasibility of these strategies is evaluated by distinguishing bench-scale findings from pilot- and industrial-scale operations, highlighting realistic constraints such as outlet temperature limits, cost, and scalability. Future research should focus on balancing probiotic viability and concentration per gram, refining encapsulation design at the microscale, applying artificial intelligence to optimize spray-drying parameters, developing cost-effective novel equipment, ensuring probiotic safety and functionality, and integrating multiple protective strategies. The paper is expected to promote the application of spray-drying in the production of probiotic powder.