Viscoelastic properties of frozen-thawed agar/agar-gelatin gels based on binary-phase virtual structure

A binary-phase finite element method (FEM) model was developed to determine the viscoelastic properties of frozen-thawed agar/agar-gelatin gels by treating the tissues as quadrilateral macro columns. The columns of the FEM geometric model consist of the shell grain boundary and a matrix. The mechanical properties of the shell were assumed to remain constant during freezing and thawing, while those of matrix portion were influenced by thermal and morphological changes. Stress-relaxation tests were carried out for three types of frozen-thawed agar gels with varying gelatin concentrations. The stress-relaxation behavior of the gels was simulated with two sets of viscoelastic parameters, one determined by nonlinear regression (NR) analysis and the other by FEM optimization, and the results compared with reference to experimental data. The prediction errors fell within 12.5% for NR analysis and 3.1% for FEM optimization, confirming the validity of the binary-phase FEM model developed in this research.