Abstract There are currently limited studies on the effect of superheated steam (SHS) on the solidification behaviour of droplets with dissolved solids which is a core phenomenon in spray drying. In this work, the single droplet drying technique was used to investigate how SHS affects the particle formation process of organic sugar droplets (lactose and mannitol), protein droplets (whey protein isolate) and droplets containing inorganic solute (sodium chloride). Unexpected droplet drying phenomenon was observed differing from drying behaviour typically assumed in the literature. While SHS is well known to result in slower drying rates below the inversion temperature, it also exhibits a lower potential to remove moisture at the end point ‘pseudo-equilibrium’ stage of drying. This led to lactose and mannitol droplets encountering incomplete moisture removal challenges in its drying process. The higher constant rate drying temperature experienced by droplet in SHS led to the precipitation of ultrafine protein particles. This higher constant rate drying temperature also led to the production of inverted pyramidal shaped salt crystals highlighting the potential of SHS as a useful medium for spray drying crystallization control.

中文翻译：

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过热蒸汽中含有有机和无机溶质的液滴的异常干燥行为

摘要 目前，关于过热蒸汽 (SHS) 对具有溶解固体的液滴固化行为的影响的研究有限，这是喷雾干燥中的核心现象。在这项工作中，单液滴干燥技术用于研究 SHS 如何影响有机糖液滴（乳糖和甘露醇）、蛋白质液滴（乳清蛋白分离物）和含有无机溶质（氯化钠）的液滴的颗粒形成过程。观察到意外的液滴干燥现象，不同于文献中通常假设的干燥行为。虽然众所周知，SHS 会导致低于转化温度的干燥速度变慢，但它在干燥的终点“伪平衡”阶段也表现出较低的去除水分的潜力。这导致乳糖和甘露醇液滴在干燥过程中遇到不完全去除水分的挑战。SHS 中液滴经历的较高恒速干燥温度导致超细蛋白质颗粒的沉淀。这种更高的恒速干燥温度也导致了倒金字塔形盐晶体的产生，突出了 SHS 作为喷雾干燥结晶控制的有用介质的潜力。