Dynamic viscoelastic properties of sweet potato studied by dynamic mechanical analyzer

The relaxation, creep, temperature-dependence and frequency-dependence characteristics of sweet potato roots were evaluated using a dynamic mechanical analyzer (DMA). The sweet potato was cut into rectangular to meet the testing requirements and wrapped with sealing film or aluminum foil to prevent water loss. The temperature scanning tests were carried out at 2 °C/min and 10 °C/min in the temperature range of 30–100 °C, and the frequency sweep tests were conducted in a range of 50–0.1 Hz. The regression results suggested that 5-element Maxwell model described relaxation behavior better for consisting of two relaxation times; the creep behavior matched the Burgers model well, and changes in creep parameters were observed after each creep cycle. The temperature scanning tests revealed that starch gelatinization was only obtained when the temperature increased at 2 °C/min. A resonance frequency was detected both in 3-point bending and compression deforming clamps.