Revolutionizing Liquid Nitrogen Spray Freezing: Core Mechanistic Insights, Multiscale Parameter Effects, and Digital Smart Innovations for Diverse Food and Biomedical Applications

Liquid nitrogen spray freezing (LNSF) has emerged as a promising technology for cryopreservation in food and biomedical applications, offering ultra-fast cooling rates and excellent heat transfer efficiency that preserve structural integrity. Despite its potential, challenges such as unstable cavitation flow, difficulty controlling atomized particle size, non-uniform heat transfer, and material heterogeneity limit its broader application. This review systematically analyzes the core physical mechanisms of LNSF — cavitation, atomization, heat transfer, and ice crystal dynamics — highlighting key controlling parameters including cavitation number (σ), Weber number (We), Ohnesorge number (Oh), and Reynolds number (Re). The effects of flow properties, nozzle geometry, ambient conditions, and surface characteristics are examined in detail. We also explore digital innovations that enable a shift from rapid to precision freezing, including multimodal sensing, predictive modeling, and adaptive control. Applications across aquatic products, fruits and vegetables, edible fungi, starch-based products, and biological tissues are discussed, emphasizing how cross-scale coupling between flow dynamics and thermophysical behavior influences freezing efficiency, ice morphology, and product quality. Systematic parameter optimization is shown to enhance freezing uniformity and reduce cryo-damage, charting a clear pathway toward next-generation precision LNSF systems.