Effect of cooking technology and chemical components on stress-relaxation property of cooked rice

Stress relaxation curves of cooked rice prepared by four cooking technologies were determined with texture analyzer and major chemical components of cooked rice were also measured. The relationship between stress-relaxation parameters and chemical components were studied in order to offer parameters for technology optimization and new cooker development. Obvious difference of stress-relaxation property could be obtained from cooked rice prepared by different cooking technologies. Cooked rice had higher hardness when rice was cooked at lower temperature. When cooked at higher temperature, cooked rice exhibited higher viscosity. The equilibrium elastic modulus E₀, retarded elastic modulus E₁, relaxation time τ, nonlinear exponential n and viscosity coefficient η of cooked rice were 15.754～89.323 Pa, 34887.528～35213.051 Pa, 0.130～0.179 s, 0.019～0.054 and 4538.085～6248.998 Pa·s, respectively. Cooked rice presented cross-linking viscoelastic behavior whose stress-relaxation parameters were related to its chemical components. Higher protein content resulted in higher E₀, τ and η of cooked rice. Cooked rice with higher fat content had smaller E₀ and with higher BV had smaller E₁ and τ. The stress-relaxation parameters of cooked rice could be well described by the multivariate power function models based on chemical components of cooked rice.