Revealing the microstructural stability of a three-phase soft solid (ice cream) by 4D synchrotron X-ray tomography

Understanding the microstructural stability of soft solids is key to optimizing formulations and processing parameters to improve the materials' properties. In this study, in situ synchrotron X-ray tomography is used to determine the temperature dependence of ice-cream's microstructural evolution, together with the underlying physical mechanisms that control microstructural stability. A new tomographic data processing method was developed, enabling the features to be segmented and quantified. The time-resolved results revealed that the melting-recrystallization mechanism is responsible for the evolution of ice crystal size and morphology during thermal cycling between -15 and -5 degrees C, while coalescence of air cells is the dominant coarsening mechanism controlling air bubble size and interconnectivity. This work also revealed other interesting phenomena, including the role of the unfrozen matrix in maintaining the ice cream's microstructural stability and the complex interactions between ice crystals and air structures, e.g. the melting and recrystallization of ice crystals significantly affect the air cell's morphology and the behavior of the unfrozen matrix. The results provide crucial information enhancing the understanding of microstructural evolution in multi-phase multi-state complex foodstuffs and other soft solids.