Submitted to: ACS Symposium Series
Publication Type: Book / Chapter
Publication Acceptance Date: 2/19/2013
Publication Date: 2/5/2014
Citation: Tunick, M.H., Onwulata, C.I., Cooke, P.H. 2014. Using temperature sweeps to investigate rheology of bioplastics. In: Tunick,M., Onwulata,C. editors. ACS Symposium Series, "Physical Methods in Food Analysis". Washington, DC: ACS Publication, chapter 7 pp. 89-104.
Technical Abstract: As part of research on extrusion of proteins for food fortification, the viscoelastic properties and microstructure of 20 percent solutions of calcium caseinate (CC), egg albumin (EA), fish protein isolate (FPI), soy protein isolate (SPI), wheat gluten (WG), and whey protein isolate (WPI) were determined under the same heating conditions. Values for elastic modulus (to determine the strength of the protein bonds) obtained from temperature sweeps from 24 to 70 deg C showed that solutions of CC, EA, and SPI produced stronger and more ordered networks than WG and WPI, and that no network was formed with FPI. Activation energies calculated from Arrhenius plots were highest for EA, SPI, and WG, which undergo sulfhydryl-disulfide bonding when heated; the other three proteins produce non-covalent bonds. Scanning electron microscopy revealed microstructural transformations indicative of changes in bonding that would be expected if the proteins were extruded. The strength of protein bonds is determined by elastic modulus and information on the types of bonds involved is provided by activation energy, enabling predictions to be made about the matrices obtained by extrusion or other processing at elevated temperatures.