title: Networks of polysaccharides with hydrophilic and hydrophobic characteristics in the presence of co-solute.
abstract: 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°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.
authors.affiliation: School of Applied Sciences, RMIT University, City Campus, Melbourne, Victoria, Australia.
authors.forename: Omar
authors.initials: O
authors.lastname: Almrhag
authors.forename: Paul
authors.initials: P
authors.lastname: George
authors.forename: Anna
authors.initials: A
authors.lastname: Bannikova
authors.forename: Lita
authors.initials: L
authors.lastname: Katopo
authors.forename: Stefan
authors.initials: S
authors.lastname: Kasapis
mesh_terms: D005936:Glucans / Q000737:chemistry / Q000648:ultrastructure; D057927:Hydrophobic and Hydrophilic Interactions; D010368:Pectins / Q000737:chemistry / Q000648:ultrastructure; D011134:Polysaccharides / Q000737:chemistry* / Q000648:ultrastructure; D012685:Sepharose / Q000737:chemistry / Q000648:ultrastructure; D012996:Solutions; D013816:Thermodynamics
chemical_list: D005936:Glucans; D011134:Polysaccharides; D012996:Solutions; D010368:Pectins; D012685:Sepharose; C033375:polydextrose