Moisture diffusivity in pasta during drying

The purpose of this work is to evaluate moisture transfer during the drying of extruded durum semolina. Effective diffusivities of pasta were determined using a stepwise drying procedure at temperatures of 40-85°C and for moisture contents of 1·5-26% db. Diffusivities ranged from 1·5 × 10^-12 to 48 × 10^-12 m²/s. The actual transient moisture profiles were measured by slicing samples that were partially dried and then frozen. The spatial resolution between data points was 0·1 mm. Drying curves and moisture profiles were predicted with the diffusion equation. The model successfully predicted the drying curves and profiles at 40°C, but for the higher temperatures the model underpredicted the drying rate and predicted steeper profiles than those measured.