Thermomechanical properties of extruded cereal melts

Little information has been published on the thermomechanical properties of corn meal and oat flour. These materials are used throughout the snack food and breakfast cereal industries. Knowing the thermomechanical spectrum of a given material is beneficial in predicting how the material will respond to a given process.;Cereal melts were produced via extrusion cooking using a Wenger TX-52 twin-screw extruder at in-barrel moisture contents ranging from 25 to 42% (wb). Sample moisture contents were chosen as being of extreme importance to the cereal processing industry. Dynamic mechanical thermal analysis using a Bohlin VOR-Melt rheometer was performed to determine the plasticizing effect of water for melts obtained from degermed corn meal, oat flour, pregelatinized corn starch and pregelatinized waxy maize.;Hydrophilic biopolymer systems reach a state of maximum plasticization at a concentration of water designated as W;For degermed corn meal, T;Extruded oat flour may have a value of W;At temperatures greater than 320K, a substantial reduction in the rubbery modulus was observed for extruded oat flour. These losses may be attributed to a reduction in physical crosslinks.;The time-temperature superposition principle was applied to the experimental data. The best fit was with an Arrhenius-type relationship rather than one described by WLF kinetics.;A more appropriate representation of the experimental data may reside in isotimic plots of viscoelastic functions. These contour plots provided information on material behavior in addition to state diagrams. These diagrams may be used to explain the relationship between the product and process as well as to guide in formulating products and setting process parameters.