Modeling Convective Drying of Food Products:The Case Study of Yacon (Smallanthus sonchifolius)

Abstract

The convective drying of a food product whose dehydration occurs under large deformation is studied. A numerical model is proposed for solving the heat and water mass transfer phenomena while accounting for shrinkage. The finite volume method is applied; mesh boundaries move with the dry matter. Shrinkage is predicted from geometrical considerations only, hence no information about the product's mechanical properties is required. Water diffusivity in the product is assumed to depend on both temperature and water content. The approach is illustrated for cylindrical samples of yacon, associated with high water content in natura and significant volume reduction after drying. This study considers previous experimental work with a convective drying pilot unit under controlled air temperature and relative humidity conditions. Numerical results reveal, firstly, that the significant evolutions of sample volume (to about 10 % of initial value) and of total water content (to less than 5 % of initial value) are quite well represented. Secondly, despite the relative homogeneity of temperature field, the water content exhibits differences between the sample surface and its core even after six hours of drying. Sensitivity tests put in evidence the major role played by the convective heat and mass transfer coefficients. The physical model and the numerical approach can be adapted in order to predict the evolution of materials with high water content in natura, which experience large deformation during the convective drying process.

CONVECTIVE DRYING KINETICS OF YACON (Smallanthus sonchifolius Poepp. Endl.) SLABS AND EVALUATION OF THE DRYER PID TEMPERATURE CONTROL SYSTEM

“…For this reason, previous studies by Bernstein and Noreña (2014); Marques et al (2023); Marques et al (2022a); and Marques et al (2022b) have studied the parameters, kinetics, and modeling of the yacon drying process. Campos et al (2016) determined the drying temperature (80 °C) for rapid dehydration without affecting the FOS content; and Gangta et al (2023) studied the pre-drying treatment to avoid browning of yacon powder.…”