Fundamental studies on the structural functionality of whey protein isolate in the presence of small polyhydroxyl compounds as co-solute

The present work deals with the changing network morphology of whey protein isolate (15%, w/w) in the presence of glucose syrup (co-solute) with concentrations ranging from 0% to 65% (w/w) in 10 mM CaCl2 solution, thus producing formulations with a total level of solids of up to 80% (w/w). Denaturation behaviour and aggregation of whey protein systems were investigated using small deformation dynamic oscillation on shear, micro and modulated differential scanning calorimetry, and confocal laser scanning microscopy. A progression in the mechanical strength of protein aggregates was observed resulting from enhanced protein-protein interactions in the presence of glucose syrup. Addition of the co-solute resulted in better thermal stability of protein molecules by shifting the process of denaturation to higher temperature, as observed by calorimetry. Observations are supported by micrographs showing coherent networks with reduced size of whey protein aggregates in the presence of high levels of glucose syrup, as opposed to thick and random clusters for systems of whey protein by itself. Glass transition phenomenon was observed for condensed protein/co-solute systems, which were treated with theoretical concepts adapted from synthetic polymer research to pinpoint the mechanical glass transition temperature

A study of Novec 649 fluid jets injected into sub-, trans- and super-critical thermodynamic conditions using planar laser induced fluorescence and elastic light scattering diagnostics

This dataset contains 4 folders that include relevant data to a study done on transcritical fluid jets within the Institute for Multiscale Thermofluids at the University of Edinburgh. Information provided varies from image and video files to tabulated data and MatLab scripts. A description of the information provided in each zipped folder has been added to facilitate finding relevant data

Thermomechanical study of the phase behaviour of agarose/gelatin mixtures in the presence of glucose syrup as co-solute

In an effort to draw attention to the subject of structure/function relationships in high-solid biopolymer mixtures, this investigation produces binary composites of agarose with gelatin and systematically increases the amount of glucose syrup, which is the co-solute in this system. Experimental work was carried out using small-deformation dynamic oscillation on shear and modulated differential scanning calorimetry. Agarose/gelatin mixtures in an aqueous low-solid environment form non-interactive bicontinuous networks. Addition of glucose syrup to the polymeric blend prevents the formation of stable double helices in the environment. Gelatin, on the other hand, better withstands the co-solute-induced change in solvent quality. At subzero temperatures, materials go through the rubber-to-glass transition whose DSC glass transition temperature (Tg) is governed by the total level of solids in the system. Estimation of the mechanical Tg acquires physical significance by utilising the theory of free volume, as modelled by the Williams, Landel and Ferry (WLF) equation. The single value of Tg estimated by this approach argues in accordance with experimental observations for the predominance of the gelatin network in the high-solid mixture

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 counterpart

Effect of whey protein agglomeration on spray dried microcapsules containing Saccharomyces boulardii

This work investigates the effect of whey protein agglomeration on the survivability of Saccharomyces boulardii within spray dried microcapsules. It attempts to go beyond phenomenological observations by establishing a relationship between physicochemical characteristics of the polymeric matrix and its effect on probiotic endurance upon spray drying. It is well known that this type of thermal shock has lethal consequences on the yeast cells. To avoid such undesirable outcome, we take advantage of the early agglomeration phenomenon observed for whey protein by adjusting the pH value of preparations close to isoelectric point (pH 4-5). During the subsequent process of spray drying, development of whey protein agglomerates induces formation of an early crust, and the protein in this molten globular state creates a cohesive network encapsulating the yeast cells. It appears that the early crust formation at a given sample pH and temperature regime during spray drying benefits the survivability of S. boulardii within microcapsules

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

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 syste

Hydrostatic pressure effects on the structural properties of condensed whey protein/lactose systems

Hydrostatic pressure effects on whey protein/lactose mixtures were recorded with subsequent analysis of their structural, molecular and glass transition properties in comparison to thermal effects at atmospheric pressure. Experimental techniques used were small deformation dynamic oscillation in shear, modulated differential scanning calorimetry, Fourier transform infrared spectroscopy, and theoretical modelling of glass transition phenomena. Levels of solids ranged from 30 to 80% (w/w) in formulations with a protein/co-solute ratio of four-to-one. Addition of lactose protects the secondary conformation of the protein under application of high hydrostatic pressure. Nevertheless, pressurized protein systems are able to form three-dimensional structures due to the reduction in polymeric free volume and the development of an efficient friction coefficient amongst tightly packed particles. Systems can be seen as developing a "molten globular state", where the structural knots of pressure-treated networks remain in the native conformation but achieve intermolecular cross-linking owing to frictional contact. Furthermore, pressure treated assemblies of condensed whey protein preparations could match the viscoelasticity of the thermally treated counterparts upon cooling below ambient temperatures. That allowed examination of the physical state and morphology of a condensed preparation at 80% solids by the combined framework of reduced variables and free volume theory thus affording derivation of glass transition temperatures for pressurized and atmospheric samples. (C) 2012 Published by Elsevier Ltd

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 (Tg) of the pectin network, whereas polydextrose assists in the formation of stronger pectin gels in the rubbery state