Publication no. C-2002-0401-05R |  VIEW ARTICLE

Thermomechanical Transitions of Rice Kernels.

Zhenhua Sun (1), Wade Yang (1), Terry Siebenmorgen (1,2), Annemieke Stelwagen (3), and Auke Cnossen (1). (1) Department of Food Science, University of Arkansas, 2650 N. Young Ave., Fayetteville, AR 72704. (2) Corresponding author. E-mail: <tsiebenm@uark.edu> Phone: 501-575-2841. Fax: 501-575-6936. (3) Department of Food Sciences, Wageningen University, The Netherlands. Cereal Chem. 79(3):349-353. Accepted November 19, 2001. Copyright 2002 American Association of Cereal Chemists, Inc.

Thermomechanical analysis (TMA) and differential scanning calorimetry (DSC) were used to investigate the thermal transitions of long-grain rice kernels. Three distinct thermomechanical transitions were identified as rice kernels were heated from 0 to 200°C. The identified transitions were a low temperature transition with onset at approximately 45°C, an intermediate temperature transition at approximately 80°C, and a high temperature transition at approximately 180°C. Low temperature transition with onset from approximately 60°C at 5% moisture content (MC) to 30°C at 20% MC was identified as the glass transition of the rice kernels. Intermediate temperature transition from 60 to 100°C, depending on MC, may be caused by rapid evaporation of moisture in the rice kernels. High temperature transition was associated with melting of the crystalline structure of rice starch. The temperatures of all three transitions decreased as MC increased, confirming that moisture acted as a plasticizer in rice kernels.