Networks of polysaccharides with hydrophilic and hydrophobic characteristics in the presence of co-solute
- 作者：Omar Almrhag ; Paul George ; Anna Bannikova ; Lita Katopo ; Stefan Kasapis ; stefan.kasapis@rmit.edu.au
- 关键词：Agarose ; Pectin ; Polydextrose ; Glass transition temperature ; Thermomechanical analysis
- 刊名：International Journal of Biological Macromolecules
- 出版年：2012
- 期刊代码：62_01418130
- 类别：abs
- 出版时间：July-August, 2012
- 卷：51
- 期：1-2
- 页码：138-145
- 文件大小：992 K
摘要
The present investigation deals with the changing network morphology of agarose and high methoxy pectin when mixed with polydextrose as co-solute at concentrations varying up to high level of solids. Thermomechanical analysis and micro-imaging were performed using small deformation dynamic oscillation in shear, modulated differential scanning calorimetry and environment scanning electron microscopy. Fourier transform infrared spectroscopy and wide angle X-ray diffraction were practised to examine the nature of interactions between polymer and co-solute, and the extent of amorphicity of preparations. We observed a decline in the mechanical strength of aqueous agarose preparations upon addition of high levels of polydextrose, which should be attributed to reduced enthalpic content of the coil-to-helix transition of the polysaccharide network. Glass transition phenomena were observed at subzero temperatures in condensed preparations, hence further arguing for the formation of a lightly cross-linked agarose network with changing solvent quality. High levels of co-solute induce formation of weak pectin gels at elevated temperatures (even at 95 掳C), which with lowering temperature exhibit increasing strength. This results in the formation of rubbery pectin gels at ambient temperature, which upon controlled cooling to subzero temperatures convert to a clear glass earlier than the agarose counterparts.