Investigation on the phase behaviour of gelatin/agarose mixture in an environment of reduced solvent quality.

Investigation on the phase behaviour of a biopolymer mixture has been performed using 7.5% (w/w) gelatin and 1.5% (w/w) agarose in the presence of variable amounts of polydextrose as the co-solute from low to high levels of total solids. Mechanical observation of the system was performed using small deformation dynamic oscillation in shear along with thermal studies using modulated differential scanning calorimetry. Micrographs provided images of the changing morphology of the network with the addition of co-solute. Agarose and gelatin form non-interactive bicontinuous phases in the aqueous environment. Systematic increase in the concentration of polydextrose prevents the formation of a stable agarose network, with the polysaccharide chains dispersing in the high solids environment. Gelatin, on the other hand, retains its conformational stability even at a saturating co-solute environment through enhanced protein structuring. Vitrification studies on the high solids system at subzero temperatures provides information on the structural and molecular relaxation identified as a glass transition phenomenon. Fourier transform infrared spectroscopy was used to analyse potential direct interaction between polymers and co-solute. The extent of amorphicity in the system was confirmed using wide angle X-ray diffraction.

Analysis on the effectiveness of co-solute on the network integrity of high methoxy pectin.

Co-solute requirements for high methoxy pectin gelation were observed by the addition of glucose syrup and polydextrose at concentrations varying from 50% to 78% (w/w). Pectin content was fixed at 2% (w/w) in formulations. Studies from small deformation dynamic oscillation in shear, modulated differential scanning calorimetry and environmental scanning electron microscopy are reported. Structural properties of pectin preparations were recorded in relation to the molecular weight and concentration of added co-solute in an acidic environment (pH ∼3.0). High levels of co-solute induce formation of weak pectin gels at elevated temperatures (even at 95°C), which upon subsequent cooling exhibit increasing strength and convert to a clear glass at subzero temperatures. 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. Glucose syrup is an efficient plasticiser leading to a reduction in the glass transition temperature (T(g)) of the pectin network, whereas polydextrose assists in the formation of stronger pectin gels in the rubbery state.

Networks of polysaccharides with hydrophilic and hydrophobic characteristics in the presence of co-solute.

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.

Phase behaviour of gelatin/polydextrose mixtures at high levels of solids.

This investigation focuses on understanding the phase behaviour of gelatin when mixed with polydextrose (co-solute) primarily at high solid concentrations. The experimental work was carried out using small deformation dynamic oscillation in shear, modulated differential scanning calorimetry, Fourier transform infrared spectroscopy, wide angle X-ray diffraction and environmental scanning electron microscopy. A progression in the mechanical strength and thermal stability of the gelatin network was observed with the addition of polydextrose to the system. Combined thermomechanical and microscopy evidence argues for the development of phase separation phenomenon between protein and co-solute in high-solid preparations, where gelatin maintains helical conformation to provide network integrity as well as glassy consistency at subzero temperature. At the high solids regime, glassy consistency was treated with theoretical frameworks from the synthetic polymer research to pinpoint the glass transition temperature of the system.