Experimental and simulation study on shrinkage of Radix Paeoniae Alba slices during drying process

Shrinkage is an important factor affecting the final quality of Radix Paeoniae Alba (RPA) slices during drying processes. In this study, drying experiments were carried out to determine the effect of the initial drying of roots on RPA slice shrinkage. The RPA root was initially dried to an initial moisture content (M0) and then cut to slices that were sequentially dried to the targeted final moisture content to decrease the shrinkage symptoms of RPA slices. In this approach, M0 should be high enough to easily slice the roots without being cracked and as low as possible to decrease the deformation of the slices during the final drying. Results showed that the shrinkage ratio of the RPA slices decreased with the decrement of M0 and the increment of drying temperature (T). At a high T (70 °C), high M0 (up to 0.45 d.b.) could be effectively used to slice and dry RPA roots with less shrinkage in the final product, whereas at a low T (50 °C), low M0 (≤ 0.35 d.b.) should be used. A 3D model with moving boundary was also developed to simulate the drying and shrinkage process of RPA slices. Simulation results showed that the model successfully predicted the moisture content and temperature of RPA slices and simulated their shrinkage behavior during drying, with reasonable accuracy.