Expansion of rice pellets: Examination of glass transition and expansion temperature
Journal
Journal of Cereal Science
Journal Volume
32
Journal Issue
2
Pages
137-145
Date Issued
2000
Author(s)
Abstract
Rice pellets were prepared by single-screw extrusion cooking at an in-barrel water content of 45 to 55 wt.%. The glass transition (T(g)) and expansion (T(e)) temperature of rice pellets has been determined by differential scanning calorimetry (DSC) and non-contact infrared thermometer, respectively. T(g) and T(e) had similar dependence on equilibrium moisture that acted as plasticiser. T(e) increased linearly with T(g) with a correlation coefficient (r2) of 0.95. T(e) was 20-100 °C higher than T(g), which indicated that the expansion of pellets occurred at the rubbery region. Maximum expansion occurred at 10% equilibrated moisture due to the transition of pellet from brittle to ductile. The addition of dextrin reduced the average molecular weight as well as T(g), but increased the expansion ratio due to decreasing the viscosity. Gordon-Taylor equation fitted well (r2 = 0.89) T(g) of the pellets without dextrin. A model has been developed to estimate T(g) for the pellet consisting of rice flour, water and dextrin. (C) 2000 Academic Press.
SDGs
Type
journal article