ORCID Profile
0000-0001-6016-7580
Current Organisation
University of British Columbia
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Publisher: Springer International Publishing
Date: 2021
Publisher: Springer Science and Business Media LLC
Date: 17-04-2202
Publisher: Elsevier BV
Date: 05-2004
Publisher: Hindawi Limited
Date: 04-2007
Publisher: Wiley
Date: 20-12-2011
DOI: 10.1002/BIP.22020
Abstract: Four molecular fractions of gelatin produced by alkaline hydrolysis of collagen were investigated in the presence of cosolute to record the mechanical properties of the glass transition in high-solid preparations. Dynamic oscillatory and stress relaxation moduli in shear were recorded from 40°C to temperatures as low as -60°C. The small-deformation behavior of these linear polymers was separated by the method of reduced variables into a basic function of time alone and a basic function of temperature alone. The former allowed the reduction of isothermal runs into a master curve covering 17 orders of magnitude in the time domain. The latter follows the passage from the rubbery plateau through the glass transition region to the glassy state seen in the variation of shift factor, a(T) , as a function of temperature. The mechanical glass transition temperature (T(g) ) is pinpointed at the operational threshold of the free volume theory and the predictions of the reaction rate theory. Additional insights into molecular dynamics are obtained via the coupling model of cooperativity, which introduces the concept of coupling constant or interaction strength of local segmental motions that govern structural relaxation at the vicinity of T(g) . The molecular weight of the four gelatin fractions appears to have a profound effect on the transition temperature or coupling constant of vitrified matrices, as does the protein chemistry in relation to that of amorphous synthetic polymers or gelling polysaccharides.
Publisher: Elsevier BV
Date: 08-2015
DOI: 10.1016/J.CARBPOL.2015.03.051
Abstract: The influence of pH on the mechanical relaxation of LM-pectin in the presence of co-solute has been investigated by means of differential scanning calorimetry, ζ-potential measurements and small deformation dynamic oscillation in shear. pH was found to affect the conformational properties of the polyelectrolyte altering its structural behavior. Cooling scans in the vicinity of the glass transition region revealed a remarkable change in the viscoelastic functions as the polyelectrolyte rearranges from extended (neutral pH) to compact conformations (acidic pH). This conformational rearrangement was experimentally observed to result in early vitrification at neutral pH values where dissociation of galacturonic acid residues takes place. Time-temperature superposition of the mechanical shift factors and theoretical modeling utilizing WLF kinetics confirmed the accelerated kinetics of glass transition in the extended pectin conformation at neutral pH. Determination of the relaxation spectra of the s les using spectral analysis of the master curves revealed that the relaxation of macromolecules occurs within ∼ 0.1s regardless of the solvent pH.
Publisher: Elsevier BV
Date: 07-2006
Publisher: Springer Science and Business Media LLC
Date: 20-01-2020
Publisher: Elsevier BV
Date: 2014
Publisher: Elsevier BV
Date: 08-2008
Publisher: Springer Science and Business Media LLC
Date: 16-07-2009
Publisher: Elsevier BV
Date: 05-2003
Publisher: MDPI AG
Date: 17-04-2023
Abstract: Glycerol is a reliable solvent for extracting polyphenols from food and waste products. There has been an increase in the application of glycerol over benchmark alcoholic solvents such as ethanol and methanol for natural product generation because of its non-toxic nature and high extraction efficiency. However, plant extracts containing a high glycerol concentration are unsuitable for mass spectrometry-based investigation utilising electrospray ionization, inhibiting the ability to analyse compounds of interest. In this investigation, a solid phase extraction protocol is outlined for removing glycerol from plant extracts containing a high concentration of glycerol and their subsequent analysis of polyphenols using ultra-performance liquid chromatography coupled with quadrupole time of flight tandem mass spectrometry. Using this method, glycerol-based extracts of Queen Garnet Plum (Prunus salicina) were investigated and compared to ethanolic extracts. Anthocyanins and flavonoids in high abundance were found in both glycerol and ethanol extracts. The polyphenol metabolome of Queen Garnet Plum was 53% polyphenol glycoside derivatives and 47% polyphenols in their aglycone forms. Furthermore, 56% of the flavonoid derivates were found to be flavonoid glycosides, and 44% were flavonoid aglycones. In addition, two flavonoid glycosides not previously found in Queen Garnet Plum were putatively identified: Quercetin-3-O-xyloside and Quercetin-3-O-rhamnoside.
Publisher: Elsevier BV
Date: 07-2010
Publisher: Elsevier BV
Date: 08-2019
DOI: 10.1016/J.CIS.2019.05.008
Abstract: Fabrication of next generation polysaccharides with interfacial properties is driven by the need to create high performance surfactants that operate at extreme environments, as for ex le in complex food formulations or in the gastrointestinal tract. The present review examines the behaviour of polysaccharides at fluid food interfaces focusing on their performance in the absence of any other intentionally added interfacially active components. Relevant theoretical principles of colloidal stabilisation using concepts that have been developed for synthetic polymers at interfaces are firstly introduced. The role of protein that in most cases is present in polysaccharide preparations either as contaminant or as integral part of the structure is also discussed. Critical assessment of the literature reveals that although protein may contribute to emulsion formation mostly as an anchor for polysaccharides to attach, it is not the determinant factor for the long-term emulsion stability, irrespectively of polysaccharide structure. Interfacial performance of key polysaccharides is also assessed revealing shared characteristics in their modes of adsorption. Conformation of polysaccharides, as affected by the composition of the aqueous solvent needs to be closely controlled, as it seems to be the underlying fundamental cause of stabilisation events and appears to be more important than the constituent polysaccharide sugar-monomers. Finally, polysaccharide adsorption is better understood by regarding them as copolymers, as this approach may assist to better control their properties with the aim to create the next generation biosurfactants.
Publisher: Sciyo
Date: 28-09-2010
DOI: 10.5772/10275
Publisher: Elsevier BV
Date: 12-2013
Publisher: Elsevier BV
Date: 12-2010
Publisher: Springer Science and Business Media LLC
Date: 14-11-2006
Publisher: Elsevier BV
Date: 03-2024
Publisher: Elsevier BV
Date: 02-2016
Publisher: Elsevier BV
Date: 12-2014
Publisher: Elsevier BV
Date: 02-2022
Publisher: American Chemical Society (ACS)
Date: 07-03-2007
DOI: 10.1021/BM0610471
Abstract: The present investigation constitutes an attempt to rationalize the effect of aging and ice structuring proteins (ISPs) on the network morphology of frozen hydrated gluten. In doing so, it employs differential scanning calorimetry, time-domain NMR, dynamic oscillation on shear, creep testing, and electron microscopy. Experimentation and first principles modeling allows identification and description of the processes of ice formation and recrystallization in molecular terms. It is demonstrated that in the absence of a readily discernible glass transition temperature in gluten-ice composites, the approach of considering the melting point and aging at constant or fluctuating temperature conditions in the vicinity of this point can provide a valid index of functional quality. A theoretical framework supporting the concept of capillary confined frozen water in the gluten matrix was advanced, and it was found that ISPs were effective in controlling recrystallization both within these confines and within ice in the bulk.
Publisher: Elsevier BV
Date: 08-2018
Publisher: Elsevier BV
Date: 11-2008
Publisher: Elsevier BV
Date: 07-2017
Publisher: Informa UK Limited
Date: 12-07-2018
DOI: 10.1080/10408398.2018.1480007
Abstract: Extrusion technology has rapidly transformed the food industry with its numerous advantages over other processing methods. It offers a platform for processing different products from various food groups by modifying minor or major ingredients and processing conditions. Although cereals occupy a large portion of the extruded foods market, several other types of raw materials have been used. Extrusion processing of various food groups, including cereals and pseudo cereals, roots and tubers, pulses and oilseeds, fruits and vegetables, and animal products, as well as structural and nutritional changes in these food matrices are reviewed. Value addition by extrusion to food processing wastes and by-products from fruits and vegetables, dairy, meat and seafood, cereals and residues from starch, syrup and alcohol production, and oilseed processing are also discussed. Extrusion presents an economical technology for incorporating food processing residues and by-products back into the food stream. In contemporary scenarios, rising demand for extruded products with functional ingredients, attributed to evolving lifestyles and preferences, have led to innovations in the form, texture, color and content of extruded products. Information presented in this review would be of importance to processors and researchers as they seek to enhance nutritional quality and delivery of extruded products.
Publisher: Elsevier BV
Date: 11-2004
Publisher: Wiley
Date: 26-10-2019
DOI: 10.1111/IJFS.14389
Publisher: Wiley
Date: 23-02-2018
Publisher: MDPI AG
Date: 03-09-2021
DOI: 10.3390/SU13179915
Abstract: This research studied the commercial exploitation of an indigenous African crop in order to formulate high value products, with a potential significant impact on the local economy. More specifically, the present work investigated the extraction of polysaccharides from baobab in a bench-scale unit, focusing on the overall yield and the techno-economic assessment of the extraction process. Preliminary technoeconomic analysis for two scenarios (with and without ethanol recycling) was performed to determine the economic viability of the process and the development of the baobab market both in Nigeria and the UK. A full economic analysis was undertaken for each of the two scenarios, considering all operating and capital costs, and the production cost of baobab polysaccharides was estimated based on a constant return on investment. Combining the operating cost with the average polysaccharide yield, the minimum profitable selling price in the UK was estimated to be between £23 and £35 per 100 g of polysaccharide, which is comparable to the commercial selling price of high purity polysaccharides. An assessment of a scaled-up plant was also performed under Nigerian conditions and the results showed that such an investment is potentially viable and profitable, with a minimum profitable selling price of £27 per 100 g, a value comparable to the UK-based scenarios.
Publisher: Springer Science and Business Media LLC
Date: 14-01-2016
Publisher: Wiley
Date: 17-02-2017
Publisher: Royal Society of Chemistry
Date: 2016
Publisher: Wiley
Date: 14-03-2019
DOI: 10.1002/JSFA.9633
Abstract: The structure and function of by-products of berry-processing industries are reviewed, with particular attention to dietary fibre (DF) and its effects in food products. The complex chemical composition and physicochemical characteristics of DF have been investigated and strategies for extraction of specific fractions that provide tailored technological and physiological functionality have been reviewed. The aim of this review is to describe in detail the structural composition and isolation methods of dietary fibre derived from berry by-products, and to explore their potential functionality in foods. The goal is to introduce DF from berry waste streams into the food chain, for which bread is a major vehicle. However, the appeal of bread lies in its aerated structure, for which DF is generally detrimental. The technological influence of DF on the formation and stabilization of the aerated structure of bread is therefore reviewed, in order to understand how to incorporate DF into bread while maintaining palatability. The aerated structure of bread is stabilized by two mechanisms: the gluten matrix and the liquid film surrounding bubbles. Incorporating DF successfully into bread requires understanding its interactions with both of these mechanisms. DF fractions from berries offer superior nutritional value compared to cereal fibre, potentially with less damage to bread structure, due to the higher proportion of soluble fibre. By-products from berry-processing industries could be used as a source of technologically and nutritionally distinctive DF to fabricate foods with enhanced nutritional value. © 2019 Society of Chemical Industry.
Publisher: Elsevier BV
Date: 06-2021
Publisher: MDPI AG
Date: 12-04-2023
DOI: 10.3390/HORTICULTURAE9040482
Abstract: Garlic is one of the most economically important crops cultivated and consumed worldwide. The rising demand for garlic in the functional food market is driven by the growing interest in using processed products and supplements for benefits in health and wellbeing. Prior to processing, freshly harvested Thai garlic undergoes six distinct curing procedures however, the losses and initial quality evaluation of the cured garlics have never been assessed. The research aims to evaluate losses and types of biomass during post-harvest processing using lab scale waste composition and mass–flow analyses, which align with the bio-circular green economic approach. Qualitative process flow diagrams (PFD) of each curing procedure were outlined, and the volume of post-harvest loss and types of biomasses were recorded. The study found that the overall losses during garlic curing were significantly higher than those associated with curing the bulb with root attached and the bulb alone. Moisture loss ( %) was the greatest type of loss, followed by through biomass during initial and minimal processing. The aerial part accounted for % of total biomass loss, while root and skin were variable, depending on whether the initial process was conducted before or after curing. In terms of quality, the study found that the total phenolic and flavonoid content of garlic decreased after curing, and the level of total reducing sugar significantly decreased from the day of harvest. This result can be used as the criterion for handling Thai garlic after harvest. In addition, the biomass produced by postharvest processing can be utilised as a raw material for biorefinery extraction.
Publisher: Springer International Publishing
Date: 2020
Publisher: No publisher found
Date: 2021
Publisher: Elsevier BV
Date: 2009
Publisher: Elsevier BV
Date: 07-2023
Publisher: Elsevier
Date: 2019
Publisher: Elsevier BV
Date: 09-2020
Publisher: IEEE
Date: 09-2018
Publisher: Elsevier
Date: 2019
Publisher: Elsevier BV
Date: 07-2019
Publisher: Elsevier BV
Date: 11-2011
Publisher: Elsevier BV
Date: 05-2006
DOI: 10.1016/J.COLSURFB.2006.03.011
Abstract: The structure and gelation kinetics of mixed linkage barley beta-glucans of varying Mw have been investigated. The fractal concept has been applied to describe the structure development of barley beta-glucan gels using a scaling model and dynamic rheometry data. The model supports that the gel structure consists of fractal clusters that upon aggregation lead to a three-dimensional network. The analysis showed that with increasing Mw a denser (more packed) network is formed as indicated by the corresponding fractal dimension (df) values. The microelastic parameter of the model, alpha, showed that all gel structures were in the transition regime implying structural reordering upon ageing. The description of the microstructure as a fractal network seems to be able to explain syneresis and other observations from large deformation testing of such systems. The molecular treatment of the gelation kinetics suggests that the gelling behavior is governed by the probability of collision of chain fragments with consecutive cellotriosyl units. This is greater for small chains due to their higher diffusion rates, for chains having lower amounts of cellulose like fragments and finally for those showing smaller degree of intrachain interactions. As a result, the faster gelling systems exhibit lower fractal dimensionality (more disordered systems) something that is in accordance with current kinetic theories.
Publisher: Wiley
Date: 25-03-2017
DOI: 10.1002/BIP.23016
Abstract: Mesoscopic structure of pectin with different molecular characteristics was investigated by means of small angle X-ray scattering (SAXS), electrokinetic measurements and data modelling. The influence of a broad range of pH (2-7) on chain conformation in the dilute and semi-diluted regime was investigated. Scattering data and concomitant analysis revealed two length scales at all environmental conditions studied. pH showed greater influence at acidic values (pH 2.0) enhancing the globular component of the structure due to association of galacturonic acid residues. Double logarithmic scattering intensity plots revealed fractal dimensions of 1.9 ± 0.2 in the low-q regime and 1.5 ± 0.2 in the high q-region, irrespectively of the specific environment. Increase in branching of RG-I regions of the polysaccharide chains enhanced the compact conformation irrespectively of the pH or concentration. The present work shows that radical changes in pectin conformation can be induced only under strongly acidic conditions a finding that has important consequences in tailoring the technological performance of these biopolymers.
Publisher: Elsevier BV
Date: 2015
Publisher: Elsevier BV
Date: 11-2017
Publisher: Elsevier BV
Date: 05-2017
Publisher: Elsevier BV
Date: 12-2012
Publisher: Elsevier BV
Date: 10-2011
DOI: 10.1016/J.IJBIOMAC.2011.05.014
Abstract: The rheological properties and microstructure of aqueous oat β-glucan solutions varying in molecular weight were investigated. The structural features and molecular weights (MW) were characterized by (13)C NMR spectroscopy and high performance size-exclusion chromatography (HPSEC), respectively. The microstructure of the β-glucans dispersions was also examined by atomic force microscopy (AFM). The s les with β-glucan content between 78 and 86% on a dry weight basis had MW, intrinsic viscosity ([η]) and critical concentration (c*) in the range of 142-2800×10(3)g/mol, 1.7-7.2dl/g and 0.25-1.10g/dl, respectively. The flow and viscoelastic behaviour was highly dependent on MW and on the concentration of the β-glucans dispersions. Pseudoplastic behaviour was exhibited at high concentrations and Newtonian behaviour was evident at low concentrations. At the same concentration, the viscosity was higher for higher MW s les. The Cox-Merz rule was applicable for the lower molecular weight s les at higher concentrations whereas the high molecular weight s le deviated at concentrations greater than 1.0%, w/v. The mechanical spectra with variation of both MW and concentration were typical of entangled biopolymer solutions. AFM images revealed the formation of clusters or aggregates linked via in idual polymer chains scattered heterogeneously throughout the system. The aggregate size increased with the molecular weight of the s les investigated and has been linked to the rheological behaviour of the s les.
Publisher: Wiley
Date: 28-11-2019
DOI: 10.1111/IJFS.14445
Publisher: Elsevier BV
Date: 09-2016
DOI: 10.1016/J.COLSURFB.2016.05.016
Abstract: Pectins with distinct molecular design were isolated by aqueous extraction at pH 2.0 or 6.0 and were examined in terms of their formation and stabilisation capacity of model n-alkane-in-water emulsions at acidic pH (pH 2.0). The properties and stability of the resulting emulsions were examined by means of droplet size distribution analysis, Lifshitz-Slyozov-Wagner modelling, bulk rheology, interfacial composition analysis, large- litude oscillatory surface dilatational rheology, electrokinetic analysis and fluorescence microscopy. Both pectin preparations were able to emulsify alkanes in water but exhibited distinct ageing characteristics. Emulsions prepared using pectin isolated at pH 6.0 were remarkably stable with respect to droplet growth after thirty days of ageing, while those prepared with pectin isolated at pH 2.0 destabilised rapidly. Examination of chemical composition of interfacial layers indicated multi-layered adsorption of pectins at the oil-water interface. The higher long-term stability of emulsions prepared with pectin isolated at high pH is attributed to mechanically stronger interfaces, the highly branched nature and the low hydrodynamic volume of the chains that result in effective steric stabilisation whereas acetyl and methyl contents do not contribute to the long-term stability. The present work shows that it is possible by tailoring the fine structure of pectin to engineer emulsions that operate in acidic environments.
Publisher: Elsevier BV
Date: 05-2023
Publisher: Springer Science and Business Media LLC
Date: 08-01-2018
Publisher: Elsevier BV
Date: 08-2015
Publisher: Elsevier BV
Date: 02-2019
DOI: 10.1016/J.IJBIOMAC.2018.10.220
Abstract: Grewia polysaccharides were isolated using sodium metabisulphite and phosphate buffers and the influence of the different extraction techniques on the chemical composition and structural characteristics of the extracts were determined. Structure and chemical composition of the resulting polysaccharide extracts were determined using FT-IR and NMR spectroscopy, neutral sugar analysis, size exclusion chromatography coupled to multi-angle light scattering (SEC-MALS), dilute solution viscometry and steady shear rheology. Chemical composition was similar irrespectively of the extraction solvent used and ranged between 11.1 and 16.5% for protein, 53.4 and 66.9% for total carbohydrate, 18.5 and 35.1% for total uronic acid and 23.5 and 28.6% for rhamnose. Predominate sugars in the extracts were rhamnose and uronic acids with spectroscopy showing the presence of esterified groups. Intrinsic viscosity varied between 6.5 and 9.1 dL g
Publisher: Wiley
Date: 30-12-2020
Publisher: Wiley
Date: 27-07-2019
DOI: 10.1002/JSFA.9891
Abstract: Pectin characteristics from different parts of lemon fruit (Citrus limon L.) were studied as a basis for assessing their suitability for functional applications. Pectin was extracted from lemon albedo, lemon core parts and membranes, and lemon extract using an aqueous extraction protocol. The composition and structural properties of the isolated pectins were examined by means of complementary analytical methods to assess their molecular characteristics for potential industrial applications. The isolation protocol yielded pectins that were predominantly composed of galacturonic acid, with differences in the degree of methylation and neutral sugars content, and with low protein content, indicating high-purity materials. The same extraction protocol resulted in differences in yield and purity between the three different parts of lemon fruit, and in structural variations in the pectin backbone, as evidenced by differences in sugar composition and molecular weight. Solutions of the isolated lemon pectins exhibited pseudoplastic behavior. Macromolecular characterization showed that the lemon extract pectin had the highest molecular weight and hydrodynamic volume, followed by lemon core and lemon albedo pectin. The work demonstrates that pectins with distinct structural properties may be extracted from different parts of lemon wastes and used for different technological purposes. © 2019 Society of Chemical Industry.
Publisher: Elsevier BV
Date: 07-2017
Publisher: Wiley
Date: 06-01-2020
DOI: 10.1111/IJFS.14483
Publisher: Elsevier BV
Date: 05-2009
Publisher: Elsevier BV
Date: 2011
Publisher: Elsevier BV
Date: 05-2013
DOI: 10.1016/J.FOODCHEM.2012.10.073
Abstract: The isothermal phase behaviour at 5 °C of mixtures of sodium caseinate and oat β-glucan isolates varying in molecular weight (MW) was investigated by means of phase diagram construction, rheometry, fluorescence microscopy and electrophoresis. Phase diagrams indicated that the compatibility of the β-glucan/sodium caseinate system increases as β-glucan MW decreases. Images of mixtures taken at various biopolymer concentrations revealed phase separated domains. Results also revealed that at the state of thermodynamic equilibrium, lower MW s les yielded considerable viscosity in the mixture. At equivalent hydrodynamic volume of β-glucan in the mixtures, s les varying in molecular weight exhibited similar flow behaviour. A deviation dependent on the protein concentration was observed for the high MW s le in the concentrated regime due to the size of β-glucan aggregates formed. Results demonstrate that by controlling the structural features of β-glucan in mixtures with sodium caseinate, informed manipulation of rheological properties in these systems can be achieved.
Publisher: Elsevier BV
Date: 04-2016
Publisher: Elsevier BV
Date: 09-2021
Publisher: American Chemical Society (ACS)
Date: 02-07-2018
Abstract: The interplay of degree of methylesterification (DM), pH, temperature, and concentration on the macromolecular interactions of pectin in solution has been explored. Small-angle X-ray scattering complemented by atomic force microscopy and molecular dynamics was employed to probe chain dimensions and solution structure. Two length scales have been observed with the first level of structure characterising chain clusters with sizes ranging between 100-200 nm. The second level of structure arises from single biopolymer chains with a radius of gyration between ∼6 and 42 nm. The development of a range of macromolecular dimensions in vitro and in silico shows that the chain flexibility increases with DM and at acidic pH, whereas hydrogen bonding is the responsible thermodynamic driving force for cluster formation. High methyl pectins create structures of lower fractal dimension with less efficient packing. This work unveils pectin conformations covering most of its industrially and biologically relevant environments, enabling rational design of advanced biomaterials based on pectin.
Publisher: Elsevier BV
Date: 07-2010
Publisher: Elsevier BV
Date: 11-2016
DOI: 10.1016/J.CARBPOL.2016.07.036
Abstract: A polysaccharide from the leaves of Sesamum radiatum was extracted by maceration in deionized water followed by ethanol precipitation then chemically and physically characterised. Monosaccharide composition and linkages were determined by high performance anion exchange chromatography (HPAEC), gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance (NMR) spectroscopy respectively. Sesamum gum was composed of glucuronic acid, mannose, galactose, and xylose with trace quantities of glucose, rhamnose and arabinose. Proton and (13)C NMR spectroscopy, and linkage analysis revealed a glucuronomannan based structure comprising a backbone of →4)-β-d-GlcpA-(1→2)-α-d-Manp-(1→ with side-chains of galactose and xylose. Hydrated sesamum gum displayed temperature independent viscoelastic properties with no thermal hysteresis. Intrinsic viscosity was determined to be 3.31 and 4.40dLg(-1) in 0.1M NaCl and deionised water respectively, while the critical concentration was determined to be 0.1% w/v. The characterisation performed in this study will help direct potential applications of this material in foods and pharmaceuticals.
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Vassilis Kontogiorgos.