Hybrid mixture theory based modeling of transport mechanisms and expansion‐thermomechanics of starch during extrusion

Abstract

Water, vapor, and heat transport mechanisms and thermomechanical changes occurring inside the expanding extrudate were described using hybrid mixture theory‐based unsaturated transport equations. Transport equations were transformed from the Eulerian coordinates to the Lagrangian coordinates. Good agreements between the predicted and experimental values of surface temperature, moisture content, and expansion ratio of the extrudates were obtained. The model was also used to calculate temperature, moisture content, pore‐pressure, and viscoelastic‐stress distribution in the extrudate. Matrix collapse and glassy crust formation under the surface was calculated as a function of extrusion conditions. Expansion behavior of the extrudate was described using the difference between stress due to pore pressure and viscoelastic stress. The modeling results can serve as a guide for predictably modifying the extrusion parameters for obtaining specific textural attributes of expanded starch for various food, feed, and biomedical applications. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4517–4532, 2015

Hybrid mixture theory‐based modeling of transport of fluids, species, and heat in food biopolymers subjected to freeze–thaw cycles

“…The temperature‐dependent deformation during freezing was estimated using the phase change strain calculated from the ratio of density of unfrozen matrix and frozen matrix. By calculating the pore pressure, the effect of fluids’ redistribution on the solid matrix can be understood, and the subsequent expansion or shrinkage in the biopolymeric matrix can be estimated (Ditudompo & Takhar, 2015; Netti et al., 2003). The pore pressure is expressed by $${P^{pore}} = {s^w}{P^w} + {s^g}{P^g}$$, where $${s^w}$$ and $${s^g}$$ are the degrees of water and gas saturation (Ehlers, 2002).…”

Modelling Volume Change and Deformation in Food Products/Processes: An Overview

“…Examples of this multiscale modelling approach include the works developed by Manepalli et al [ 58 ], van der Sman and Broeze [ 166 ], and Wang et al [ 167 ]. Likewise, Ditudompo and Takhar [ 168 ] utilized a two-scale multiphase model based on the hybrid mixture theory (HMT, previously described), coupled with poroviscoelasticity equations to describe transport processes and mechanical changes in extruded products during expansion.…”

Incorporating food microstructure and material characteristics for developing multiscale saturated and unsaturated transport models

“…An interesting aspect of this study was that porosity of the starch matrix could be calculated along the cross-section of starch using fundamental hybrid mixture theory based equations coupled to poroviscoelasticity relations discussed in [39]. The model was also used to calculate temperature, moisture content, glassy crust formation, expansion ratio, pore-pressure and viscoelastic-stress distribution across the cross-section of extrudate as function of distance from the die nozzle [10]. The microstructural and rheological characteristics of model calculated by numerical simulations would require several years to measure experimentally.…”