Developing Supra-Molecular Structures During Freeze-Drying of Food

In this contribution, we discuss a scientific approach to controlling the freeze-drying process in order to obtain products with desired attributes, using two examples. In the first part, the freeze-drying kinetics of a model food are recorded and represented using a state diagram, which was then used to optimize a strategy to preserve the physical structure and minimize the drying time of the product. The second part focuses on the application of freeze drying to produce amorphous sucrose coatings. In this study, model food materials have been coated with a liquid sucrose solution, and freeze-dried on a laboratory scale. The drying kinetics have been measured and plotted on a sucrose state diagram in order to optimize the process conditions and to minimize possible crystallization. Analysis of the physical state of the sucrose (using DSC, NIR, and microscopy) showed that a dominantly amorphous coating was obtained. Compared to a crystalline reference, the amorphous sucrose dissolved more quickly in a liquid, inducing a faster sweetness perception. This result also opens new opportunities for sugar reduction in food due to an enhanced sweetness perception.