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Temperature induced interactions between β-casein and ferulic acid were investigated under ultra-high temperature (UHT) conditions (140 °C) utilising a variety of spectroscopic methods. Fluorescence measurements indicate that structural alterations to the protein have occurred; the resulting red shift in tryptophan peak fluorescence with increasing concentrations of ferulic acid indicates that the single tryptophan residue has become more exposed to the polar environment. This evidence is further supported by Fourier transform infrared (FTIR) and circular dichroism (CD) measurements showing an increase in irregular and intermediary structural components upon addition of ferulic acid, as well as UV-vis measurements that record an increase in absorption. High performance liquid chromatography (HPLC) work strongly argues that the ferulic acid is bound covalently to the protein post heat treatment. This outcome is in agreement with molecular docking simulations and quantum mechanics calculations that indicate the formation of a covalent bond between ferulic acid and glutamine54 residue of β-casein to create a new adduct.

The purpose of this research is to investigate swellable genipin-crosslinked gelatin matrices for the controlled delivery of water soluble vitamins (ascorbic acid). The following methods were utilized to describe the physicochemical properties of the system: micro differential scanning calorimetry and small deformation dynamic oscillation in shear. Hydrogel microstructural properties were reported in terms of the average molecular weight between crosslinks and network mesh size. Degree of crosslinking in gels with concentration of genipin crosslinker from 0 to 2.8% (w/w) was measured using ninhydrin assay and UV-vis spectroscopy. Swelling of the gel matrix in aqueous solvent was followed and colorimetric methods were used to measure the diffusion kinetics of ascorbic acid from the gel to the surrounding aqueous phase. Results after treatment of swelling data with improved Fickian theory found matrix swelling was limited by the relaxation of polymer chains. Significance of results lies in the derivation of apparent diffusion coefficients for the transport of water molecules and bioactive compound at 85% and 98% crosslinking that relates the kinetics of bioactive compound release to mesh size of the polymeric network. Thus, there is strong evidence that modulation of the extent of crosslinking impacts on hydrogel morphological characteristics and structural properties, with resulting control of bioactive compound release. Outcomes may be implemented in targeted delivery of bioactive compounds, including vitamins, within the human body, for improved bioavailability.

Delivery of techno- and bio-functionality in all-natural processed foods is an area of steadily increasing fundamental and technological interest. One of the main aspects in this field is based on the diffusion of natural bioactive compounds that have been incorporated in high-solid biopolymers matrices. Organoleptic considerations dictate that the delivery vehicles are characterised by a highly amorphous fraction in the biopolymer network. Molecular diffusion in the amorphous state is a complex process associated with the effect of the glass transition temperature (Tg) on the mobility of low molecular-weight bioactives. This work will review the molecular dynamics of high-solid biopolymer systems, and model food preparations in the presence of co-solute, in relation to the diffusion kinetics of natural bioactive compounds. Literature indicates that the metastable properties of condensed biopolymer networks traversing the rubber-to-glass transition region affect significantly the diffusion kinetics of bioactive compounds. These have been modelled using concepts from the classical and improved diffusion theory to unveil a relationship between apparent diffusion coefficient of bioactives and free volume characteristics of the condensed biopolymer network. Further work is required in added value foods, sourcing inspiration from the “sophisticated pharmaceutical research”, to develop food systems that control transport phenomena for targeted release from a specific dosage form.

A fundamental study was carried out to evaluate patterns of vitamin B6 release from genipin crosslinked gelatin in aqueous media at ambient temperature. Up to ninety percent crosslinking was achieved, with FTIR and WAXD data arguing for partial replacement of the triple helix with a covalent pattern of bonding between protein and crosslinker. Formation of a “composite network” yielded increasing compressive stress-at-failure values followed by a decrease as a function of genipin addition, with the yield strain decreasing continuously. Electron microscopy images showed a reduction in the size of the hydrogel pores with a higher degree of crosslinking. Experimental evidence was supported by the Flory-Rehner theory that predicted a lower swelling ratio and reduced molecular weight between adjacent crosslinks with genipin addition. Furthermore, Peppas-Sahlin equation was used to rationalise the interplay between network morphology and diffusion of bioactive compound over prolonged timeframes of release testing.

The impacts of sonication on functional properties of lupin protein isolates derived from lupin flour was investigated. The lupin protein isolates of pH 5 and 9 were then treated with low-frequency ultrasound throughout an energy density range of 457–2746 J/mL. The physicochemical and functional properties including particle size, solubility, zeta potential, rheological, thermal properties and molecular weight of the samples were measured. Ultrasound treatment was effective in reducing the particle size of the lupin protein isolates for the pH 5 sample to less than 10 μm, and less than 1 μm for the pH 9 suspension. Ultrasound also increased the solubility of lupin protein across the pH profile. Zeta potential wasn't affected to any significant extent, as it remained unchanged at −5 for the pH 5 protein isolate, and −27 mV for the pH 9 protein sample after ultrasound treatment. Following sonication, the viscosity of the pH 5 lupin protein increased, where the highest viscosity measurement of 1000 mPa s being achieved for the sample sonicated at an energy density of 1830 J/mL; in contrast, viscosity decreased with higher energy densities for the pH 9 sample. The storage modulus behaviour demonstrated the efficacy of ultrasound for improving the gelling properties of the lupin protein samples at pH 5, with 4000Pa being measured upon sonication at an energy density of 2746 J/mL; on contrast, the pH 9 sample possessed poor gelling properties despite ultrasound treatment. Finally, the DSC curves indicated an inverse correlation between the energy density of ultrasound treatment and enthalpy.

There is a substantial volume of research articles in the field of protein-ligand interactions, with a large proportion using inappropriate methodology for the fluorescence spectroscopy analysis of binding interactions. The most common issues being overlooked are the inner filter effect and the use of unsuitable equations to calculate binding strength and stoichiometry, leading to the propagation of questionable methodology and reported results throughout multiple fields. In this communication, we carefully explain these issues and approaches to overcome them, including accounting for the inner filter effect, the use of appropriate equations to obtain dissociation constant (Kd) values (as opposed to the commonly misused Stern-Volmer equation), and carefully dealing with binding stoichiometry using the Job plot (often misjudged using the Hill coefficient instead). We hope that the work will bring attention to critical and often common issues in fluorescence spectroscopy, as well as improving the approaches used in the binding analysis of protein-ligand systems. Thus, it should provide a good example of how to go about this type of research, as well as being of interest to the broad readership of the journal.

Metastable properties of biopolymer networks affect significantly the diffusion kinetics of bioactive compounds. That was shown to be the case in high solid samples of protein and polysaccharide supporting a homogeneous distribution of polyunsaturated fatty acids. Thermomechanical behaviour of these matrices was characterised in relation to their glass transition temperature ( T g ). A free volume theory of diffusion was considered to treat transport phenomena of fatty acids within glassy polymers. It was found that at T > T g the effective diffusion coefficient of microconstituent transport would increase in accordance with the free volume of the polymer matrix. Fitting experimental diffusivity data in glassy polymers to a free volume based theory generates a two-parameter equation that calculates the extent of molecular interaction between macromolecule and microconstituent. Gradual substitution of polymer with small-molecule co-solute, glucose syrup in this case, induces a plasticising effect that profoundly affects the level of interaction, hence the diffusion of fatty acids in the condensed biomaterial.

This study deals with the distribution of added calcium ions and their effect on the phase behaviour of hydrogels made of bovine serum albumin and gelatin. Structural properties of single and mixed systems were identified using small-deformation dynamic oscillation in shear, microdifferential scanning calorimetry and scanning electron microscopy. The experimental procedure was designed to encourage formation of micro phase-separated materials, where i) a continuous gelatin matrix supported liquid BSA inclusions, ii) an inverted dispersion of gelled BSA was interspersed by liquid gelatin inclusions and iii) a rigid BSA phase supported softer filler particles of gelatin. The Lewis-Nielsen equations and a series of models developed by Takayanagi were adapted for predicting the phase behaviour of BSA/gelatin mixtures in the presence of added calcium chloride. As far as we are aware, this is the first attempt to model the partition of added counterions between polymeric phases in binary hydrogels based on classic blending law analysis.

The classical limiting case of simple diffusion as described by Fick's second law was examined in the transport of a small molecule, linoleic acid, through a condensed polymer matrix, whey protein. Experimental protocol was based on small-deformation dynamic oscillation in-shear, wide angle X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, FTIR microspectroscopy imaging, ANS fluorescence spectroscopy, and the sulfo-phospho-vanillin assay. This mass transfer problem for the omega-6 fatty acid was examined in relation to whey protein forming a glassy system with a glass transition temperature, Tg, of ?16 °C. Diffusion followed a more complicated pattern than Fick's equation that could be described at temperatures above Tg with the so-called anomalous transport. The diffusion coefficient of linoleic acid was estimated within the glass transition region and glassy state of the whey protein network delineated with changing environmental temperature. The free-volume theory of transport was then considered to provide a useful vehicle for rationalising molecular motion and, in doing so, we established a generalised relationship between diffusion coefficient of bioactive compound and fractional free volume of polymeric matrix.

Vitamin entrapment in matrices made of natural polymers and its controlled release has application to a variety of added value foods and nutraceuticals. This communication utilises data from published literature on the molecular transport of vitamin B6 from condensed matrices of genipin-crosslinked gelatin, bovine serum albumin and whey protein isolate to develop a mechanistic model that accounts for moving boundary conditions. In doing so, it utilises the apparent diffusion coefficient of the micronutrient, the molecular weight of the uncrosslinked polymer chain and the average molecular weight between neighbouring crosslinks. The derived mathematical expression for swellable matrices in an aqueous environment can follow the progression of diffusivity with degree of crosslinking in the polymeric excipients. Model fitting provides a minimisation parameter, which is interpreted in terms of the extent of coupling between solute diffusion and matrix structural relaxation. Parallel predictions of polymer network mesh and critical molecular weight between crosslinks indicate that values of normalised size well above one are required for anomalous (non-Fickian) release due to obstructed diffusion.

Structural relaxation of a delivery vehicle has been identified in the literature as a limiting parameter for the controlled diffusion of a bioactive compound. To further examine the kinetics of controlled release, this study designed a system of homogeneously dispersed linoleic acid in a high-solid whey protein matrix. Amorphous glucose-syrup liquid was added systematically up to about 48% (w/w), with the total solids level in the formulation being kept constant at 80% (w/w), and experimental observations were obtained over a broad timeframe and temperature range. Structural and physicochemical properties of the blend were monitored using dynamic oscillation in-shear, WAXD, FTIR and confocal laser scanning microscopy. A specific chromogenic reaction with UV–vis spectroscopy was employed to follow the release of linoleic acid under perfect sink conditions. Variation in the amount of glucose syrup, as the co-solute, within the high-solid whey protein network affected profoundly the values of the mechanical glass transition temperature. That was reflected in the kinetics of fatty acid diffusion from the glass transition region of our composite materials. Transport phenomena were quantified via the concept of effective diffusion coefficient, which increases with higher levels of glucose syrup leading to structural relaxation of the delivery vehicle.

The structural relaxation properties of high-solid gelling polysaccharides, gelatin and whey protein with small-molecule co-solutes have been reviewed focusing on the glass transition region and glassy state of the mechanical master curve. Compliance with the principle of thermorheological simplicity is established allowing horizontal superposition of viscoelastic functions in the form of small-deformation stress relaxation or dynamic oscillation modulus. Numerical calculations via the Tikhonov regularization yield smooth stress relaxation spectra over a broad timescale that encompasses the isothermal process of vitrification in these systems. Next, the molecular coupling theory addressed the polymer chain dynamics of the local segmental motions that determine the glass transition temperature (Tg) of condensed matrices. Thus a more complete picture of the physics of intermolecular interactions in the short-time region of the glass dispersion has emerged. It allows estimation of the relaxation time for local segmental motions at Tg, and the extent of cooperativity between adjacent chemical moieties governing kinetics of viscoelastic relaxation in hydrocolloid based systems at the glass transition region.

Interactions between β-casein and 4-hydroxybenzoic acid (4HBA) were investigated following ultra-high temperature (UHT) treatment at 140 °C for 10 s. The aim of the work was to identify the binding strength, binding stoichiometry and type of molecular interactions between protein and bioactive compound. Molecular dynamics (MD) analysis shows that binding is stabilised by a wider variety of residues than is often indicated in simpler docking studies. Construction of Job plots via fluorescence quenching argues that β-casein can accommodate two 4HBA molecules. This is in agreement with MD analysis, which demonstrates the stability of ligand in two different binding sites of the receptor. FTIR results indicate a binding interaction between the two components and UV–vis measurements record an increase in the absorption of 4HBA following UHT treatment in the presence of β-casein. The latter observation argues that 4HBA may be bound covalently following heat treatment. This is further supported by MD simulations and quantum mechanics calculations that indicate one site has the potential for binding covalently to 4HBA via the lysine32 residue of the β-casein molecule. This work addresses often overlooked issues in the determination of binding parameters, through the use of the method of continuous variation for the accurate determination of binding stoichiometry, as well as making use of a nonlinear fluorescence binding equation to account for the residual fluorescence of formed complexes. The findings give a broader understanding of the fate of bioactive ingredients in UHT treated beverage systems, allowing industry to make informed decisions on the inclusion of insoluble fibres and the impact of heat treatment on their products.

Plant proteins are rapidly becoming more of a prime interest to food manufactures as consumers are shifting away from meat-based diets. Therefore, food manufactures need to incorporate functional plant proteins as ingredients into their products. Lupin has a high protein (~40%) and fibre (~40%) content, is low in starch and gluten free hence, it can have an important role. Despite its nutritional and proven health benefits, lupin is underutilised and still does not play a major role in the human diet. Concentrating its protein and producing lupin protein isolate with suitable properties would make it attractive as a high protein and functional ingredient for food manufacturing. Over the recent years the industry has shown interest in large scale production of lupin protein isolate and improving its techno-functional properties. This paper reviews the literature on different lupin protein isolation techniques and conditions. The impact of protein isolation technique on chemical composition, yield and physiochemical properties including solubility, water holding capacity, molecular weight and particle size distribution, of the resultant protein isolates, are compared and contrasted. Moreover, major functional properties such as viscosity, gelling, emulsification, and thermal properties of the isolated proteins are reviewed. Varied extraction yields and largely different properties and functionalities are achieved for different lupin protein extraction techniques. In the light of the unique composition and nutritional properties of lupin seed and its protein component, future research for improving the protein isolation process for lupin and improving its physical functionalities using innovative technologies are discussed.

Delivery of techno- and biofunctionality in all-natural processed foods is an area of steadily increasing fundamental and technological interest. We prepared a range of condensed biopolymer-vitamin systems and monitored the kinetics of bioactive compound release as a function of environmental temperature. Distinct patterns of structural relaxation were noted for the polymer matrix and microconstituent above the glass transition temperature of the high-solid sample. Then, there was a qualitative agreement between fractional free-volume of polymer and effective diffusion coefficient of vitamin within the glass transition region. These observations encouraged us to develop for the first time a mathematical expression that argues for linearity in the relationship between diffusion coefficient and inverse of fractional free volume yielding the so-called decoupling parameter of polymeric motion and small-molecule diffusion. Quantifying the cooperativity of vitamin and biopolymer interaction allows informed manipulation of bioactivity release, and the generic nature of the fundamental treatise invites validation in systems beyond the current range.

Condensed systems of 25% (w/w) bovine gelatin (Mw = 173 kDa) or 25% (w/w) fish gelatin (Mw = 60 kDa) with 59% (w/w) glucose syrup and 1% (w/w) nicotinic acid to a total solids level of 85% (w/w) were prepared in this study. Analysis was carried out using Fourier transform infrared spectroscopy (FTIR), wide angle X-ray diffraction (WAXD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and small deformation dynamic oscillation in-shear. Work allowed elucidation of the micromolecular and macromolecular properties focusing on the estimation of the mechanical (Tgm) and calorimetric (Tgc) glass transition temperature of these systems. A combined protocol of free volume and reaction rate theories was considered to rationalise results in the vicinity of the glass transition region. Following this, a diffusion procedure of nicotinic acid was set up over a wide temperature range (from 5 to −40 °C) using UV–vis spectroscopy and an appropriate chromogenic reaction to detect the presence of the bioactive compound. Time dependence of the mass transfer of nicotinic acid throughout the delivery vehicle of gelatin/co-solute was followed using diffusion theory. The treatise unveiled the correlation between structural relaxation of the vitrified matrix and release kinetics of the diffusant.

This work explores the process of alginate molecule crosslinking to form cohesive gels that were induced by the addition of calcium ions at various stoichiometric equivalents. Polysaccharide gels were used as a delivery vehicle for the study of transport phenomena of entrapped caffeine as the bioactive compound. Initial physicochemical characterisation through FTIR and WAXD of the alginate matrix showed successful inclusion of caffeine in the bulk system. Rheological analysis in the form of dynamic oscillation in-shear highlighted issues of developing network integrity and its eventual collapse with increasing levels of the crosslinker. Swelling in neutral solvent (water molecules) yielded information on the molecular features of the gel, as determined by the Flory-Rehner theoretical framework. Analysis of molecular transport with modified Fickian diffusion equations showed anomalous behaviour and a sustained release of caffeine. Overall, alteration in mesh size and diffusion parameters can be ascribed to the microstructural changes controlled by calcium crosslinking and the formation of junction zones in the alginate network.

Interactions between β-lactoglobulin and ferulic acid were investigated at ambient temperature in relation to the dimer and monomer forms of the protein at pH 7.3 and 2.4, respectively. To this end, molecular dynamics (MD) simulations and a variety of spectroscopic methods were employed. Circular dichroism (CD) and Fourier transform infrared (FTIR) analysis indicate that the secondary structure of the protein is altered upon complexation, suggesting molecular interactions do occur in both the monomer and dimer forms. However, UV–vis measurements of β-lactoglobulin remain constant upon complexation with ferulic acid, indicating that interactions are non-covalent in nature and are likely stabilised by hydrophobic forces and hydrogen bonds. Fluorescence quenching confirms the presence of a binding state, with the monomeric complex producing a stronger dissociation constant than the dimeric counterpart. Docking studies and MD simulations indicate that the preferred binding site in the dimer form (pH 7.3) lies at the interface of the two monomers. In contrast, the preferred binding site for the monomer form (pH 2.4) lies within the calyx shaped β-barrel structure and is stabilised by hydrogen bonds and π - alkyl interactions.

The effect of high pressure on thermomechanical and physicochemical properties of ovalbumin samples up to 80% (w/w) solids is presented and compared to conventional thermal treatment. Results from small deformation dynamic oscillation in shear, modulated differential scanning calorimetry (MDSC) and Fourier transform infrared spectroscopy (FTIR) revealed that pressure-treated ovalbumin maintains its native conformation in condensed systems of 80% (w/w) solids, whereas its structure has been irreversibly changed in the aqueous environment of 20% (w/w) solids, and partially altered at intermediate levels of solids (30–60%, w/w). That was rationalized on the basis of specific rearrangements between sulfhydryl and disulphide bonds following application of high pressure and the high hydrophobicity of the ovalbumin molecule. Cooling to subzero temperatures results in vitrification and the formation of a matrix with glassy consistency for both atmospheric and pressurised materials. Application of the method of reduced variables and the combined WLF/free volume theoretical framework are able to predict the glass transition temperature of condensed ovalbumin preparations.

This investigation deals with the diffusional mobility of essential fatty acids in triglyceride form (oleic acid) from a condensed matrix comprising 3% (w/w) high-methoxy pectin and 81% (w/w) co-solute (glucose syrup) to absolute ethanol. Work utilises rheological measurements in shear, differential scanning calorimetry, ESEM, FTIR and WAX diffraction to identify the molecular properties of the composite system. Results showed that the amorphous carbohydrate matrix underwent vitrification at −15 °C (mechanical T g ) calculated mathematically using the Williams, Landel and Ferry (WLF) and modified Arrhenius equations. Diffusion kinetics of the fatty acid (monitored via UV-vis spectroscopy) was combined with the newly introduced concept of spectroscopic shift factor to demonstrate that, although the increment of oleic acid mobility appeared to respond to the predicted glass transition temperature, this is distinct from the structural relaxation of the matrix. Experimental observations were further treated with the concept of diffusion coefficient to provide an estimate of the transport rate of the triglyceride as a function of time or temperature of observation within the glass transition region.

The structural behaviour of soy glycinin systems following application of industrially relevant high hydrostatic pressure (600 MPa for 15 min at ambient temperature) was investigated throughout the experimental range up to 80% (w/w) solids content, and results were compared to conventional thermal treatment. Using small-deformation dynamic oscillation in shear, modulated differential scanning calorimetry, infrared spectroscopy and X-ray scattering, it was demonstrated that soy glycinin with twelve disulphide linkages displays extensive unfolding at low to intermediate solid levels (30–60%, w/w). In contrast, it largely maintains native conformation at 70 and 80% (w/w) solids showing about 20% denaturation, as compared to the thermal transition of native counterparts. Experimental data from infrared spectroscopy also argue for retention of the native conformation in condensed soy glycinin systems comprising mainly beta sheets in the secondary structure. At subzero temperatures, condensed glycinin at atmospheric and pressurised conditions undergoes vitrification phenomena recording experimental glass transition temperatures. Experimental data were successfully modelled using theoretical frameworks for mechanical studies on amorphous synthetic polymers.

The relative mobility of ascorbic acid incorporated in a condensed matrix of high-methoxy pectin (HMP) and polydextrose is reported. Physicochemical and structural characterisation of the high-solid systems utilised modulated differential scanning calorimetry, small deformation dynamic oscillation in shear, scanning electron microscopy, Fourier transform infrared spectroscopy and wide angle X-ray diffraction. Theoretical modeling of the thermomechanical measurements demonstrated that the mechanism of free volume governs stress relaxation phenomena of the polymeric system through the process of vitrification yielding the mechanical glass transition temperature. Combination of UV-vis spectrophotometry and a vitamin-dye binding method was employed to follow for 60 min the diffusion process of ascorbic acid from the concentrated HMP/polydextrose matrix to the absolute ethanol phase throughout the temperature range of −30 to 20 °C. A relatively low estimate of activation energy for the diffusion of vitamin C reflects its freedom of mobility and high free volume, as compared to the relaxation of the polymeric system that exhibits strong temperature dependence in the glass transition region. Utilisation of the concept of diffusion coefficient sheds further light into the relationship between free volume of the polymeric system and diffusional mobility of the micronutrient.

Diffusion patterns of nicotinic acid were evaluated following its microencapsulation into a whey protein matrix through spray drying. Micro-differential scanning calorimetry, small-deformation rheological techniques, wide-angle X-ray scattering, Fourier transform infrared spectroscopy, particle size analysis and scanning electron microscopy were utilised to characterize encapsulant and bioactive compound in the composite material. UV–vis spectroscopy, the newly introduced concept of spectroscopic shift factor and the Konig reaction were also employed to elucidate the rate of vitamin transport throughout the polymeric matrix as a function of a broad time and temperature spectrum. Mechanical properties of the condensed matrix followed a progression that was described with the combined Williams-Landel-Ferry/free volume theory leading to the prediction of the mechanical glass transition temperature. Modified Arrhenius equation demonstrated that the kinetics of nicotinic-acid mobility were distinct from the structural relaxation of the polymeric segments. The former was further examined using the second law of Fickian diffusion. A direct relationship between fractional free volume of the whey protein network and diffusion coefficient of the nicotinic acid was established within the experimental temperature range.

Present work investigates the effectiveness of using whey protein isolate as an encapsulant for a biotherapeutic agent ( Saccharomyces boulardii ) under varying concentrations of protein and CaCl 2 . Viability of S. boulardii within the matrix of whey protein is highly dependent on the physicochemical properties of the protein network, and its response to various environmental stress factors including processing temperature, moisture content and change in pH. Our interest is to optimise the spray drying conditions of whey protein isolate, through observations from differential scanning calorimetry and small deformation dynamic oscillation on shear, in relation to the denaturation and subsequent aggregation of the globular molecules. It is evident from this work that protein concentration is directly proportional to the strength of the network, but inversely proportional to the denaturation temperature. Increasing concentrations of calcium chloride have a direct influence on electrostatic repulsion between protein molecules thus creating a better protein structure. Development of a cohesive network was used as a basis of manipulating the viability of S. boulardii under given conditions of spray drying. Analysis on spray dried powders suggests that whey protein preparations at the isoelectric point (pH ∼5) and with CaCl 2 additions of 50–100 mM act as an efficient encapsulant providing high viability of S. boulardii .

The present investigation deals with the effectiveness of high pressure processing as a preservation technique for protein based materials. Increasing protein concentration up to 80% (w/w) in bovine serum albumin (BSA), soy glycinin and ovalbumin systems results in overall reduction in foodborne pathogens (i.e. Staphylococcus aureus, Bacillus cereus and Escherichia coli) for atmospheric samples due to reduced water activity. Application of high pressure (600 MPa for 15 min) reduces further microbial counts in these systems at comparable levels of solids. The effect of high hydrostatic pressure on proteolytic activity of proteases from Pseudomonas fluorescens strains 73 and 113 with globular proteins as substrates throughout the experimental range of protein concentration (10–80% w/w) has also been observed. Enzymatic activity in samples pressurized at 600 MPa for 15 min declined considerably, as compared to atmospheric counterparts. In addition, glycinin with the highest water holding capacity exhibits increased protease and microbiological activity at a given level of solids and treatment. Our work demonstrates that high pressure processing can act as an effective means of reducing microbial and enzymatic activity in condensed systems of globular proteins.

The formation of heat induced whey protein isolate (WPI) and wheat starch (WS) gels in the presence of added calcium chloride (5–192 mM) has been examined. Thermal properties, including the onset temperature of starch gelatinization and protein denaturation, are defined by low amplitude oscillation on shear and modulated temperature differential scanning calorimetry. Upon heating and subsequent cooling, comparison of the storage modulus values bear information on the enhancement of protein aggregation by the electrolyte and the occurrence of phase separation phenomena between the two polymeric constituents in the mixture. Further confirmation of observed trends has been provided by measurements on textural hardness of gels in single cycle compression tests. Porous and aggregated microstructures are identified upon visual examination by environmental scanning electron microscopy. The gels were subjected to in vitro enzymatic hydrolysis and the role of calcium in reducing the extent of starch degradation by α-amylase has been established. It is evident from the results that ionic strength in the form of added calcium ions largely influences gelation kinetics of whey protein leading to significant variability in the hydrolytic potential of α-amylase on wheat starch.

The work prepared high-solid mixtures of whey protein or bovine serum albumin with an amorphous co-solute (glucose syrup) and examined their glass transition behaviour at subzero temperatures. The interest in these condensed matrices was in relation to what extent thermal denaturation and subsequent aggregation of the proteinaceous molecules affects vitrification and, therefore, they were subjected to distinct heating regimes followed by cooling. Small-deformation dynamic oscillation in shear is known to respond to changes in network formation as a function of thermal treatment, albeit published reports thus far focused on low-solid aqueous hydrocolloid samples, and it has been chosen presently to examine the viscoelasticity of their high-solid counterparts. Results were further compared with those from a micromolecular technique, i.e. modulated differential scanning calorimetry. It appears that thermally induced cross-linking is readily recorded in what is known in the literature as the mechanical or network glass transition temperature, whereas the calorimetric Tg is not affected by the extent of polymeric associations in these mixtures. Further, the thermal protocol employed presently results in considerable differences in predictions of the mechanical Tg, which should reflect distinct three dimensional morphologies in these systems of globular protein and co-solute.

The rheological and structural changes in heat induced pastes and gels of lentil starch and lentil protein composites were investigated at various starch to protein ratios. The starch fraction ( φ s ) in the mixtures was varied from 0 to 1 and the total solid content was maintained at 25% (w/w). Results showed that the gel strength of the composite gels increased exponentially with the increase in lentil starch fraction. The pasting temperature increased and the paste viscosity decreased with the increase in the lentil protein fraction. The high starch composite gels ( φ s > 0.5) showed higher elastic ( G ′) and loss ( G ″) moduli at higher temperature (60 °C) than at lower temperature (10 °C). The high protein composite gels ( φ s ≤ 0.5) showed higher G ′ and G ″ values at lower temperature (10 °C) than at higher temperature (60 °C). Segregation of protein-rich domains was observed in the high starch gels ( φ s > 0.7) whereas low starch composite gels ( φ s ≤ 0.5) appeared more homogeneous. The microstructure of composite gels appeared to be more fragile with larger pore size and thinner wall compared to the microstructure of starch gel. Both non-covalent interactions (hydrophobic and hydrogen bonding) and covalent bonding were found to contribute to the gel structure and firmness of these composite gels. The NaCl concentration increased the paste viscosity and gel firmness of the composite gels up to 0.25 mM above which the magnitudes of these parameters were decreased. Both the paste viscosity and the gel firmness of the composite gels were found to be higher above the isoelectric point of lentil protein and vice versa. From this study, textural properties of the composite gel/paste were found to be strongly affected by the proportion of the starch and protein as well as the extrinsic factors (pH, ionic strength, presence of reducing agents). Therefore, understanding of gelling behaviour of lentil starch and protein in composite gel would be helpful for structure formation of these two biopolymers in mixtures and would help their application in new product development.

High hydrostatic pressure was applied on immunoglobulin samples whose molecular, structural and glass transition properties were examined in comparison to thermal effects at atmospheric pressure. Immunoglobulins exhibit pressure stability throughout the experimental concentration range by conserving native conformation, which results in cohesive structure formation observed by small-deformation dynamic oscillation on shear, modulated differential scanning calorimetry and infrared spectroscopy. Application of the combined WLF/free volume theoretical framework demonstrates that pressurised immunoglobulin preparations are able to form glassy systems upon cooling at subzero temperatures. This has been attributed to a reduction in polymeric free volume under pressure and the development of an efficient friction coefficient amongst tightly packed particles that link to form a three-dimensional matrix. Pressure treated assemblies of condensed immunoglobulins demonstrate viscoelastic behaviour matching that of the thermally treated counterparts, but retain bioactivity, which is largely lost with thermal treatment.

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.

It has been demonstrated that industrial polysaccharides (agarose, deacylated gellan and κ-carrageenan) form networks of reduced enthalpic content in the presence of high levels of non-crystallizing co-solute (e.g., glucose syrup) that exhibit time–temperature dependent behaviour of a typical rubberlike polymer. In contrast, amylose holds its structural characteristics unaltered and does not reach a state of molecular mixing with glucose syrup, with morphological features being those of a micro phase-separated mixture. Variation in phase morphology and density of intermolecular associations leads to entropic or enthalpic viscoelasticity in systems, and it was utilised to define distinct classes of food related biomaterials exhibiting an extensive glass transition region or absence of vitrification phenomena. The approach was extended to encompass the experimental parameters of a porous matrix and the application of hydrostatic pressure. In the former, work discusses discrepancies in the Tg – porosity relationship attributable to the different extent to which the two techniques of calorimetry and mechanical spectroscopy respond to degrees of molecular mobility. In the latter, it was shown that the time–temperature–pressure equivalence of synthetic amorphous polymers is not operational in the glass-like behaviour of high sugar systems in the presence of gelatin or gelling polysaccharides. The existing body of evidence allowed quantitative treatment of results based on the asymmetric distribution theory of molecular relaxation time that identifies the chemical fingerprint of the local motions operating at the vicinity of Tg. Furthermore, the diffusional mobility of a bioactive compound within a glassy matrix could be followed in relation to temperature induced changes in free volume using the time–temperature superposition principle.

Present investigation aims to study the effect of prolonged ultrasonication (more then 30 min) on the molecular weight ( M ¯ w ) and crystallinity index (CrI) of bacterial cellulose (BC) and plant cellulose (PC), and to compare the trend of M ¯ w reduction and CrI increment. In addition, the kinetics of degradation will be computed based on first order reaction kinetics. BC and PC were dissolved in cuprammonium hydroxide (CUAM) solution prior to ultrasonication at 0, 5, 10, 15, 30, 60 and 90 min. Samples were recovered from solution and lyophilised before subjected to size exclusion chromatography (SEC) measurement and x-ray powder diffraction (XRPD) studies. Ultrasonication significantly (p M ¯ w of both BC and PC, with limiting molecular weight (Mlim) of ∼47 and ∼46 kDa, respectively, after 60 min of ultrasonication. This suggests that CUAM is a more appropriate solvent in ultrasound depolymerisation of cellulose. Kinetics study reveals that degradation of BC is slightly faster than that of PC. A continuous increment of CrI as a function of ultrasonication time was observed for both BC and PC. This increment stops at samples sonicated beyond 60 min, confirming the correlation of CrI to the M ¯ w of these materials.

A composite filler was developed using a gelatin matrix that suspended fibers of microcrystalline cellulose (MCC). Structural properties of the material were evaluated with small-deformation dynamic oscillation on shear. The experimental routine achieved orientation of the MCC fibers, which led to an increase in network strength, as compared to mixtures with unoriented fibers. Enhanced mechanical properties were modeled with a mathematical expression that argued for an array of fiber orientations ranging from transversely isotropic to orthotropic systems.

The food industry relies increasingly on soluble fibre to formulate products with superior structural properties, mouthfeel and potential health benefits. In this paper, we have compiled experimental data from a wide range of high-solid foodstuffs in order to demonstrate the utility of fibre inclusion in such preparations. Recent studies have mapped out the structural properties of soluble-fibre polysaccharides (e.g., κ-carrageenan, agarose and deacylated gellan) in the presence of increasing levels of co-solute with application to the confectionery and ice cream industries. One of the incentives to understand the behaviour of such systems is the prospect of providing an alternative to gelatin since the protein is increasingly falling “out of fashion” with consumers and producers alike. This rather underresearched area has other applications, for example, flavor encapsulation and preservation of bioactive molecules in glassy polysaccharide matrices. A second example relates to the development of minced fish products which are made traditionally with added starch but fail to offer a new marketing position. The eating quality of processed fish products can be improved by including in the formulation the right amount and type of soluble-fibre polysaccharides (e.g., κ-carrageenan or low methoxy pectin) thus taking advantage of their multifaceted functionality as instrumental/sensory texture modifiers. Finally, in oriental foods, such as instant-rice noodle, gum ghatti and fenugreek gum have been utilized in an effort to improve textural attributes and mouthfeel. In addition, α-amylase inhibition by incorporation of green-tea extracts has been considered as an avenue for glycemic response reduction in model starch systems.

The effect of alginate with distinct content of guluronate sequences on the structural properties and in vitro digestion of rice dough has been investigated. Materials were engineered to serve as a model system of instant soup-based rice noodles available in the market. Alginate set externally with calcium within the dough matrix reduced cooking loss and soluble starch leakage following boiling of preparations. Small-deformation dynamic-oscillation monitored the structural properties of alginate networks, which were capable of supporting the starch granules in a cohesive composite gel. Scanning electron microscopy afforded tangible evidence of the dramatic effect of the polysaccharide network on the morphology of rice dough. Fourier transform infrared spectroscopy probed at the molecular lever the efficiency of external setting to deliver calcium ions at the vicinity of the carboxyl groups of the alginate chain. It appears that the continuous alginate phase encapsulates starch granules thus retarding in vitro digestion of the rice dough. Results are promising for the development of commercial rice noodles with superior appearance, textural profile and digestibility.

The present work investigates the effect of aging and ice-structuring proteins at low levels of solids (0.1% w/w) on the physical properties of frozen flour–water mixtures (37.5% w/w moisture). Differential scanning calorimetry, nuclear magnetic resonance, dynamic oscillation on shear, creep testing and electron microscopy were employed to explore the underlying molecular aspects of dough deterioration. Starch granules are embedded in a continuous rather than a fibrous gluten network and it was found that in such a system ice recrystallization as opposed to cryo-dehydration is the mechanism responsible for alteration of the structural characteristics of the material on storage. Deterioration of the mechanical properties continued unabated for 30 days of aging with the ice-structuring proteins being unable to offer protection against recrystallization at the concentration level studied (0.1% w/w). Furthermore, storage near the melting point of ice of the flour–water sample was found to accelerate the structural losses owing to increasing water mobility at this regime.

It is accepted in the literature that the viscoelastic properties of amorphous synthetic polymers in the rubber-to-glass dispersion relate to different modes in the time/temperature domain. The protocol of thermorheological simplicity as manifest through the combined WLF/free volume theory constitutes an early attempt to understand the nature of vitrification in spite of its obvious drawback of considering that all molecular retardation and relaxation processes have the same temperature dependence. Increasingly, thermorheological complexity is being recorded in the superposition of mechanical spectra in the viscoelastic master or composite curve, which is an observation that cannot be readily addressed. The newly proposed coupling theory aims to emphasize the distinct temperature dependence of molecular processes within the rubber-to-glass softening dispersion, thus identifying the local segmental motions as the main contributor to the viscoelastic spectrum at the vicinity of the glass transition temperature. Predictions of the coupling theory have explained the “anomalous” experimental facts in the viscoelasticity of amorphous synthetic materials, and the recently established relaxation time—intensity of intermolecular interaction correlations in the vitrification of the gelatin/co-solute mixture.

The microstructural and mechanical properties of acid-set mixtures of sodium caseinate (2% w/w)/barley β - glucans (2–6% w/w) were studied in an effort to evaluate the effect of these polysaccharides on the texture of fermented dairy products. The phase behavior of the blends was investigated using small deformation dynamic oscillation, differential scanning calorimetry, optical microscopy, and polymer blending-laws analysis. The work aimed to assess the topology of the phase separated mixture, the water holding capacity of its polymeric phases, and the thermal stability of the constituent networks. The mixed network properties were dominated by the protein component at low concentrations of β-glucans (≤3% w/w). In the concentrated regime, the system seems to have a bicontinuous topology governed by the mechanical strength and thermal stability of the β-glucan network structure. Results could assist in optimising the use of sodium caseinate and β-glucans as functional or as bioactive ingredients in acid-set dairy products.

A cursory exploration of the recent literature on the vitrification of food materials using a scientific search engine downloads a plethora of documents. Thermal analysis has been an effective tool in mapping out the physical behaviour of pure ingredients, but it has not been the technique of choice in synthetic polymer research for the rationalisation of molecular dynamics in the rubber-to-glass transition. A new concept of ‘the network T g ’ has been developed using small deformation mechanical analysis and a combination of the WLF/free volume theory with the modified Arrhenius equation. The network T g is distinct from the empirical DSC T g and the two indicators should be used in tandem to rationalise phase phenomena in biomaterials. Applications of the network T g are explored in model confections, dehydrated foodstuffs, state diagrams and adsorption isotherms.