Analyzing the microstructure of a fresh sorbet with X-ray micro-computed tomography: Sampling, acquisition, and image processing

X-ray micro-computed tomography and image processing techniques were used to analyze fresh frozen sorbets at the outlet of a batch freezer. Sorbets made from water and sucrose were visualized and their microstructure was quantified with a resolution of 9 μm. Sodium iodide was confirmed to enhance the contrast between the unfrozen water and ice in sorbets. A thermostated box was employed to keep the samples at frozen state and constant temperature (close to −6 °C) during imaging. A reproducible quantification of size distributions and volume fractions of ice crystals and air bubbles were obtained. Data concerning ice crystals were in agreement with cryo-SEM imaging. Ice crystals represented approximately 50%wt of the product and their mean size was about 60 μm whereas air bubbles represented about 6% of the volume. Finally, X-ray microtomography equipped with a thermostated box was found to be a particularly relevant technique for the analysis of the microstructure of frozen desserts.