Cereal Chem. 73 (4):433-438 |
Effect of Glass Transition and Cross-Linking on Rheological Properties of Zein: Development of a Preliminary State Diagram.
H. Madeka and J. L. Kokini (1). (1) Center for Advanced Food Technology, Department of Food Science, Rutgers-The State University of New Jersey, P.O. Box 231, New Brunswick, NJ 08903-0231. Accepted March 25, 1996. Copyright 1996 by the American Association of Cereal Chemists, Inc.
Rheological properties and thermal properties are used to characterize the physical states of zein. In this research, the transition temperature from glassy to rubbery state of Sigma zein and purified zein was measured with differential scanning calorimetry (DSC) at various moisture contents. The temperature and frequency dependence of storage (G(prime)) and loss (G(double prime)) moduli were obtained for Sigma zein with 15-35% moisture. Zein showed a networking reaction in the temperature range of 65-160°C for moistures >=25%. Below 65°C, zein behaved like an entangled polymeric fluid. As the temperature exceeded 160°C, the cross-linked/aggregated zein softened. A preliminary state diagram of zein as a function of temperature and moisture content was developed.