Development of the basics for the production of defined amorphous - crystalline core-shell particles during convective drying

• Applicant: Professorin Dr.-Ing. Petra Först
• Subject Area: Mechanical Process Engineering ; Chemical and Thermal Process Engineering
• Term: from 2017 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 346774683

Drying, handling and storing of sugar-rich powders are still a challenging task. This is due to the fact that sugars exist in different physical states, namely the glassy, rubbery and crystalline state. The physical state has a significant impact on the powder properties, e.g. on the rehydration behavior and the chemical or biological stability. Especially during phase transitions, the powder properties can deteriorate, e.g. caking of particles can occur. When the sugars are crystallized in a controlled way during drying, caking of the powder is prevented. However, the rehydration properties and the powder stability (growing of microorganisms, degradation reactions) are better in the glassy state. Particles characterized by a glassy core and a crystalline shell would combine the advantages of both physical states. However, detailed knowledge of the process and the product is necessary to manufacture such particles. This detailed knowledge is missing up to now. This project aims at closing this gap. The following relationships must be examined:1. identifying the relationship between the glass transition temperature , the sticky point , the crystallization behavior and the composition of the sugar2. Investigation of the influence of the drying kinetics and the product temperature on the crystallization behavior and the physical state of the sugar mixturesIn this project, it shall be studied how sugars in sugar mixtures interact and behave with regard to their physical state during convective drying and targeted rehydration. The project is based on the following hypotheses:The mechanisms which are relevant when drying sugar mixtures shall be identified and studied using thin-film drying, rehydration and storing. Apart from drying kinetics, the project concentrates on the stability and characteristics of the produced films. It shall be studied how the glass transition influences the stability during storage (hygroscopicity, stickiness, crystalline fraction, molecular mobility). Thus, a deeper knowledge shall be gained of the mechanisms in sugar mixtures which lead to specific powder properties during drying and controlled rehydration.

• DFG Programme: Research Grants
• Co-Investigator: Dr.-Ing. Iris Schmitz-Schug