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Creep Deformation Modeling of Glutinous Rice Cakes (Mochi)

¹Department of Hospitality Management, Mingdao University, 369 Wen-Hwa Rd., Peetow, Chang Hua, Taiwan. ²Graduate Institute of Food Science and Technology, National Taiwan University, 1, Roosevelt Road, Section 4, Taipei, Taiwan. ³Corresponding author. Phone: +886-2-3366-4121. Fax: +886-2-2362-0849. Email: yehs@ntu.edu.tw

The viscoelastic properties of glutinous rice cakes (mochi) made by extrusion at different conditions (water contents of 45–55% and barrel temperatures of 75–95°C) and commercial rice cakes were studied by a creep test. The maximum compliances of extruded mochi were 0.15–4.23 1/kPa. Among the extruded samples, the mochi extruded at 75°C with a water content of 55% was the one that yielded the largest maximum compliance. At the same barrel temperature, the creep compliance increased with the water content. Four models with different numbers of elements (spring and dashpot) were employed to fit the experimental data. The model coefficients were able to provide the corresponding elastic and viscous behavior of the sample. The 3-element model (a spring in series with a Kelvin-Voigt model) did not exhibit steady-state compliance as observed in the experimental data. The 4-element (Burger's model), modified 4-element (an approximation of Burger's model), and 6-element model (adding one more Kelvin model to the Burger's model) yielded R² > 0.99. Results showed that the 4-element model was adequate to describe the creep behavior of mochi.