Hydration study of soy protein in the ‘dry state’
No Thumbnail Available
Date
2008-05-19
Journal Title
Journal ISSN
Volume Title
Publisher
Royal Society of Chemistry
Abstract
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.
Description
Keywords
Hydration, Soybeans, Moisture, Proteins, Ambient temperature, Concentration ratio, Infrared spectrometers, Australia, Small angle scattering, Glycine
Citation
Kealley, C., Rout, M. K., Appelqvist, I., Strounina, E., Whittaker, A., Gidley, M., Gilbert, E., & Lillford, P. (2008). Hydration study of soy protein in the ‘dry state’. Paper presented to the 14th Gums and Stablisers for the Food Industry Conference, 18-22 June 2007, NEWI, Wrexham UK. In P. A. Williams & G. O. Phillips (Eds.), Gums and Stabilisers for the Food Industry (Chapter 14 : pp. 87-95). The Royal Society of Chemistry. doi:10.1039/9781847558312-00087