Effect of water and tri(ethylene) glycol on the rheological properties of zein

Before conducting larger scale studies utilizing highly concentrated zein blends on an extruder, it is advisable to carry out experiments on a torque rheometer. Water and tri(ethylene glycol) (TEG) are known plasticizers for zein, however, the effects these materials have on zein rheology has not been studied using a torque rheometer. The amount of each plasticizer in zein was varied between 5 and 30%. It was demonstrated that water and TEG interact differently with zein. When the amount of water was above 10% at 90 °C, torque increased rapidly. With TEG, torque increased linearly with time and only at 120 °C did the rapid torque increase occur. Multiple torque increases for zein mixtures were observed, suggesting that processes that increase viscosity are an on-going process. Significant cross-linking is not the main source for the increased torque. The energy of activation of flow was determined when using 20% TEG. A model was developed relating %water, %TEG, temperature and rpm with initial torque.