Using Temperature Sweeps To Investigate Rheology of Bioplastics

摘要

The viscoelastic properties and microstructure of 20 g per 100 g solutions of calcium caseinate, egg albumin, fish protein isolate, soy protein isolate, wheat gluten, and whey protein isolate were determined under the same heating conditions. Scanning electron microscopy revealed microstructural transformations indicative of changes in bonding that would be expected if the proteins were extruded. Values for elastic modulus (G') obtained from temperature sweeps from 24 to 70℃ showed that solutions of calcium caseinate, egg albumin, and soy protein isolate produced stronger and more ordered networks than solutions of the other three proteins. Activation energies (E_a) calculated from Arrhenius plots were highest for egg albumin, soy protein isolate, and wheat gluten, which undergo sulfhydryl-disulfide bonding when heated; the other proteins produce non-covalent bonds. The strength of protein bonds is determined by G' and information on the types of bonds involved is provided by E_a, enabling predictions to be made about the matrices obtained by processing at elevated temperatures.