Glass transition in pasta drying: Advanced modeling of the glassy layer evolution

In the context of pasta drying, where accurately predicting temperature and moisture content distributions is crucial, modeling and simulation play a pivotal role. The primary aim of this study is the theoretical assessment of how operating conditions impact glass transition during pasta drying to ensure a safe, high-quality product. An advanced model was developed, incorporating the transition of pasta into a glassy state based on the Kwei's model. The equations governing the drying process and the behavior at the pasta-fluid interface were solved using the finite element method, estimating the influence of air properties on process performance. The evolution of the glassy layer was analyzed, demonstrating the formation of a rigid and compact layer starting at the solid-fluid interface. The proposed model is shown to be a versatile tool, adaptable to a wide range of process and fluid-dynamic conditions in commercial pasta dryers. Model validation was performed in a pilot-scale drying chamber using inlet air at 90 °C with relative humidity levels of 40% and 60%, yielding deviations between theoretical predictions and experimental data of less than 10%.