Browsing by Author "Lillford, PJ"

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    Hydration induced structural changes in native, denatured and protected soy glycinin (11s)
    (Institute of Food Technologists, 2007-07) Appelqvist, IAM; Rout, MK; Chanvrier, H; Dezfouli, M; Kelly, M; Htoon, AK; Kealley, CS; Gilbert, EP; Strounina, E; Whittaker, AK; Gidley, MJ; Lillford, PJ
    Proteins and other biomolecules undergo a dynamic transition to a glass-like solid state with small atomic fluctuations. This dynamic transition can inhibit biological function and alter their material properties.
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    Hydration study of soy protein in the ‘dry state’
    (Royal Society of Chemistry, 2008-05-19) Kealley, CS; Rout, MK; Appelqvist, IAM; Strounina, EV; Whittaker, AK; Gidley, MJ; Gilbert, EP; Lillford, PJ
    The work reported focuses on the methodology employed by the Australian Food Futures collaboration to the study of proteins in the dry state. To date, 'dry' proteins (here used to describe solids with a moisture content <30% w/w) have been characterised by differential scanning calorimetry (DSC), fourier transform - infrared spectroscopy (FT-IR), 1H t2 relaxation and 13C high resolution nuclear magnetic resonance (NMR) spectroscopy and small angle x-ray scattering (SAXS). The case study presented in this paper centres on the use of these techniques to characterise the differences in structure between native and denatured glycinin, a soy protein, at low and controlled moisture contents. The glass transition temperature of native soy glycinin (11S) at room temperature (∼ 27°C), is at a moisture content of 13.4%, whereas the denatured soy glycinin undergoes a glass transition at 46°C at the same moisture content. With increasing water content, NMR experiments show that proton exchange with protein surfaces (*H T2) and protein segmental mobility (13C) both increase. A β - sheet toβ - turn structural rearrangement is inferred as the position of the Amide-I FT-IR band shifts from 1634 to 1630 cm"1. Proton T2 relaxation rates range from < 1 ms to 25 ms, with shorter (< 1 ms) relaxation rates dominant up to 17.4% moisture for both native and denatured glycinin. ,13C NMR experiments show motional heterogeneity for native glycinin, with a more uniform and restricted mobility after denaturation. Small angle scattering data show an expansion of -7% in the unit cell of the material as the moisture content is increased from 4.6% up to 13.4%, however there are no significant crystalline or other major structural changes in the protein over the spatial dimension probed (1-100 nm). © The Royal Society of Chemistry 2008.
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    Processing of novel elevated amylose wheats: functional properties and starch digestibility of extruded products
    (American Chemical Society, 2007-11-15) Chanvrier, H; Appelqvist, IAM; Bird, AR; Gilbert, EP; Htoon, AK; Li, ZY; Lillford, PJ; Lopez-Rubio, A; Morell, MK; Topping, DL
    Different types of novel wheat lines with different starch contents and amylose/amylopectin ratios, relating to defined alterations in the number and activity of starch synthase IIa genes, were processed by pilot-plant extrusion. Two types of products were produced: pure wholemeal products and breakfast cereals made from wholemeal/maize blends. Lower apparent shear viscosity was obtained in the extruder with lower starch content and higher amylose/amylopectin ratio flours (SSIIa-deficient line). The bulk density of the products decreased with increasing extrusion temperature and was always higher for the triple-null line. The bulk density was not completely explained by the melt shear viscosity, suggesting the importance of the fillers (fibers, brans) in the process of expansion and structure acquisition. The different mechanical properties were explained by the density and by the material constituting the cell walls. Enzyme-resistant starch (RS) content and hydrolysis index (HI) were not correlated to the extrusion temperature, but RS was higher in pure wholemeal products and in the SSIIa-deficient line. These results are discussed in terms of starch molecular architecture and product microstructure. © American Chemical Society
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    Structure and molecular mobility of soy glycinin in the solid state
    (American Chemical Society, 2008-10) Kealley, CS; Rout, MK; Dezfouli, MR; Strounina, E; Whittaker, AK; Appelqvist, IAM; Lillford, PJ; Gilbert, EP; Gidley, MJ
    We report a multitechnique study of structural organization and molecular mobility for soy glycinin at a low moisture content (<30% w/w) and relate these to its glass-to-rubber transition. Small-angle X-ray scattering (SAXS), differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy are used to probe structure and mobility on different length and time scales. NMR (similar to 10(-6) to 10(-3) s) reveals transitions at a higher moisture content (> 17%) than DSC or SAXS, which sample for much longer times (similar to 10 to 10(3) s) and where changes are detected at > 13% water content at 20 degrees C. The mobility transitions are accompanied by small changes in unit-cell parameters and IR band intensities and are associated with the enhanced motion of the polypeptide backbone. This study shows how characteristic features of the ordered regions of the protein (probed by SAXS and FTIR) and mobile segments (probed by NMR and DSC) can be separately monitored and integrated within a mobility transformation framework. © 2008, American Chemical Society