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Structural characterisation of pre-processed thermoplastic protein derived from bloodmeal

Additives are required to convert bloodmeal powder into an extrudable thermoplastic protein-based bioplastic. These include a protein denaturant, a surfactant, a reducing agent and plasticisers. The objective of this work was to assess the structural changes induced in bloodmeal by these additives prior to extrusion. Structure was investigated using Fourier transform infrared (FT-IR) spectroscopy, wide angle X-ray scattering (WAXS) and synchrotron light based FT-IR microspectroscopy. FT-IR results suggested the additives reduced α-helical content. The shape of the amide I region (1600 – 1700 cm⁻¹, representing carbonyl group stretching in the protein backbone) is known to depend on protein secondary structures. Bloodmeal showed a broad, convoluted peak in this region, with a maximum in the range 1648 – 1658 cm⁻¹, associated with α-helices. With processing additives, a dip was seen in the α-helix region, with twin peaks emerging either side of it. Urea, one of the additives, also absorbs in the amide I region and may also contribute to a change in its shape. Analysis of the amide 3 region supported a reduction in the ratio of α helices to β sheets. Further support of structural changes was shown by WAXS. The additives decreased the sharpness of peaks corresponding to 4.8 Å and 10 Å, thought to represent intra-helix spacing and inter-helix packing respectively. FT-IR microspectroscopy at the Australian Synchrotron enabled spatial variations in secondary structure to be explored using peaks in the amide 3 region. Spatial distribution of secondary structure was detected in bloodmeal and thermoplastically modified bloodmeal prior to extrusion (PPM-TEG). Bloodmeal showed domain separation on the approximate order of 10 μm, whilst PPM-TEG appeared to have larger phases and overall reduced α-helical content, relative to beta sheets.
Conference Contribution
Type of thesis
Bier, J. M., Verbeek, C. J. R. & Lay, M. C. (2012). Structural characterisation of pre-processed thermoplastic protein derived from bloodmeal. In Proceedings of Chemeca 2012: Quality of life through chemical engineering: 23-26 September 2012, Wellington, New Zealand. (pp. 1157-1166).
Engineers Australia
This article has been published in the proceedings of Chemeca 2012: Quality of life through chemical engineering. Used with permission.