Showing items 1 - 7 of 7

Glass-transition behaviour of plasticized starch biopolymer system - A modified Gordon-Taylor approach

- Chaudhary, Deeptangshu, Adhikari, Benu, Kasapis, Stefan

  • Authors: Chaudhary, Deeptangshu , Adhikari, Benu , Kasapis, Stefan
  • Date: 2010
  • Type: Text , Journal article
  • Relation: Food Hydrocolloids Vol. 25, no. 1 (2010), p. 114-121
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  • Description: Two plasticizers namely, glycerol and xylitol, based on their similar molecular size ( 6.3 Å) but different molecular weights (Glycerol-92; Xylitol-152) were selected for studying the glass-transition behaviour (rubber like behaviour) in multi-plasticized starch biopolymer with about 70% amylopectin structure. In the calorimetry measurements, glass-transition temperatures (onset temperature for bulk viscous flow) of plasticized samples were higher than non-plasticized samples at low water activities, thus showing typical antiplasticization behaviour. However, when plasticizer concentration was increased up to 15% and 20% wt, all plasticized samples showed significant reduction in glass-transition temperature. We used a modified Gordon-Taylor model to understand the competitive plasticization of glycerol and xylitol in presence of water, and suggest that competitive plasticization exists and occurs at a threshold amount of matrix free water content, due to strong three-way interactions: starch-plasticizer, plasticizer-plasticizer/water and starch-water. This competitive interaction is significant in determining the onset temperature for viscous flow behaviour; at higher matrix water content, the Gordon-Taylor constant was relatively unaffected by the plasticizer amount, and water was the dominant plasticizer. A new interaction parameter that separates the starch-plasticizer interaction in a starch-plasticizer-water system is also discussed. © 2010 Elsevier Ltd. All rights reserved.
  • Description: 2003008289

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

- Dissanayake, Muditha, Kasapis, Stefan, George, Paul, Adhikari, Benu, Palmer, Martin, Meurer, Barbara

  • Authors: Dissanayake, Muditha , Kasapis, Stefan , George, Paul , Adhikari, Benu , Palmer, Martin , Meurer, Barbara
  • Date: 2013
  • Type: Text , Journal article
  • Relation: Food Hydrocolloids Vol. 30, no. 2 (March 2013), p. 632-640
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  • Description: 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.

Interfacial and emulsifying properties of lentil protein isolate

- Joshi, Matina, Adhikari, Benu, Aldred, Peter, Panozzo, Joe, Kasapis, Stefan, Barrow, Colin

  • Authors: Joshi, Matina , Adhikari, Benu , Aldred, Peter , Panozzo, Joe , Kasapis, Stefan , Barrow, Colin
  • Date: 2012
  • Type: Text , Journal article
  • Relation: Food Chemistry Vol.134 no.3 (2012), p.343-1353
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  • Description: The dynamic interfacial tension (DIFT) at oil-water interface, diffusion coefficients, surface hydrophobicity, zeta potential and emulsifying properties, including emulsion activity index (EAI), emulsion stability index (ESI) and droplet size of lentil protein isolate (LPI), were measured at different pH and LPI concentration, in order to elucidate its emulsifying behaviour. Sodium caseinate (NaCas), whey protein isolate (WPI), bovine serum albumin (BSA) and lysozyme (Lys) were used as benchmark proteins and their emulsifying property was compared with that of LPI. The speed of diffusion-controlled migration of these proteins to the oil/water interface, was in the following order: NaCas > LPI > WPI > BSA > Lys, while their surface hydrophobicity was in the following order: BSA > LPI > NaCas > WPI > Lys. The EAI of emulsions stabilised by the above proteins ranged from 90.3 to 123.3 m 2/g and it was 93.3 ± 0.2 m 2/g in LPI-stabilised emulsion. However, the stability of LPI-stabilised emulsions was slightly lower compared to that of WPI and NaCas-stabilised emulsions at the same protein concentration at pH 7.0. The ESI of LPI emulsions improved substantially with decrease in droplet size when protein concentration was increased (20-30 mg/ml). Reduction of disulphide bonds enhanced both the EAI and ESI compared to untreated samples. Heat treatment of LPI dispersions resulted in poor emulsion stability due to molecular aggregation. The stability of LPI-stabilised emulsions was found to decrease in the presence of NaCl. This study showed that LPI can be as effective emulsifiers of oil-in-water emulsions as are WPI and NaCas at ≥20 mg/ml concentrations both at low and neutral pH. The emulsifying property of LPI can be improved by reducing the intra and inter-disulphide bond by using appropriate reducing agents. © 2012 Elsevier Ltd. All rights reserved.

Physicochemical and functional characteristics of lentil starch

- Joshi, Matina, Aldred, Peter, McKnight, Stafford, Panozzo, Joe, Kasapis, Stefan, Adhikari, Raju, Adhikari, Benu

  • Authors: Joshi, Matina , Aldred, Peter , McKnight, Stafford , Panozzo, Joe , Kasapis, Stefan , Adhikari, Raju , Adhikari, Benu
  • Date: 2013
  • Type: Text , Journal article
  • Relation: Carbohydrate Polymers Vol. 92, no. 2 (2013), p. 1484-1496
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  • Description: The physicochemical properties of lentil starch were measured and linked up with its functional properties and compared with those of corn and potato starches. The amylose content of lentil starch was the highest among these starches. The crystallinity and gelatinization enthalpy of lentil starch were the lowest among these starches. The high amylose: amylopectin ratio in lentil starch resulted into low crystallinity and gelatinization enthalpy. Gelatinization and pasting temperatures of lentil starch were in between those of corn and potato starches. Lentil starch gels showed the highest storage modulus, gel strength and pasting viscosity than corn and potato starch gels. Peleg's model was able to predict the stress relaxation data of these starches well (R2 > 0.98). The elastic modulus of lentil starch gel was less frequency dependent and higher in magnitude at high temperature (60 °C) than at lower temperature (10 °C). Lentil starch is suitable where higher gel strengthened pasting viscosity are desired. © 2012 Elsevier Ltd.
  • Description: 2003011035

Physicochemical and functional properties of lentil protein isolates prepared by different drying methods

- Joshi, Matina, Adhikari, Benu, Aldred, Peter, Panozzo, Joe, Kasapis, Stefan

  • Authors: Joshi, Matina , Adhikari, Benu , Aldred, Peter , Panozzo, Joe , Kasapis, Stefan
  • Date: 2011
  • Type: Text , Journal article
  • Relation: Food Chemistry Vol. 129, no. 4 (2011), p. 1513-1522
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  • Description: Lentil protein isolate (LPI) extract was converted into powder by freeze drying, spray drying and vacuum drying. Differences in particle size distribution, protein subunit composition and colour and surface morphology were observed amongst the three drying methods. Spray and freeze-dried LPI powders exhibited higher solubility (81% and 78%, respectively) compared to vacuum dried powders (50%). The spray dried powders showed a low water absorption capacity (0.43 ± 0.02 g/g) compared to freeze (0.48 ± 0.02 g/g) and vacuum-dried (0.47 ± 0.01 g/g) LPI powders. Spray and freeze-dried powders displayed better gelation ability and higher gel strength, compared to vacuum-dried powder. Both spray and freeze-dried gels showed typical viscoelastic gel characteristics, with G′ dominating over G″ and very low loss tangent. The holding time required for gelation of vacuum dried powder at 90 °C was significantly longer, compared to spray and freeze dried powders. Hence, drying methods used for preparation of lentil protein isolate powders can affect physicochemical and associated functional properties. © 2011 Elsevier Ltd. All rights reserved.

Structural behaviour in condensed bovine serum albumin systems following application of high pressure

- Savadkoohi, Sobhan, Bannikova, Anna, Kasapis, Stefan, Adhikari, Benu

  • Authors: Savadkoohi, Sobhan , Bannikova, Anna , Kasapis, Stefan , Adhikari, Benu
  • Date: 2014
  • Type: Text , Journal article
  • Relation: Food Chemistry Vol. 150, no. May (2014), p. 469-476
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  • Description: The present study shows that application of high hydrostatic pressure of 600 MPa for 15 min at ambient temperature on condensed bovine serum albumin systems (BSA) with up to 80% w/w solids content has a limited effect on the conformational structure of the protein, as compared to thermal treatment. This was demonstrated throughout the experimental concentration range using small-deformation dynamic oscillation, differential scanning calorimetry and infrared spectroscopy. BSA possesses seventeen disulfide linkages per molecule, which constitutes a stable arrangement with high energy requirements for substantial structure alteration. Upon cooling, pressurised materials undergo vitrification and networks exhibit comparative mechanical strength to that of thermally treated counterparts. The mechanical manifestation of the glass transition region and glassy state for atmospheric and pressurised samples was examined by the method of reduced variables and the combined framework of WLF/free volume theory producing disparate predictions of the glass transition temperature for the two types of polymeric network. © 2013 Published by Elsevier Ltd.

Unexpected high pressure effects on the structural properties of condensed whey protein systems

- Dissanayake, Muditha, Kasapis, Stefan, Chaudhary, Vinita, Adhikari, Benu, Palmer, Martin, Meurer, Barbara

  • Authors: Dissanayake, Muditha , Kasapis, Stefan , Chaudhary, Vinita , Adhikari, Benu , Palmer, Martin , Meurer, Barbara
  • Date: 2012
  • Type: Text , Journal article
  • Relation: Biopolymers Vol. 97, no. 12 (2012), p. 963-973
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  • Description: We show that application of high hydrostatic pressure (600 MPa for 15 min) on condensed whey protein (WP) systems (e.g., 80% w/w solids content) results in unexpected structure-function behavior when compared with conventional thermal treatment. Unraveling the relaxation properties in first-order thermodynamic transitions, the manifestation of glass transition phenomena and the preservation of native conformation in condensed preparations were recorded using small-deformation dynamic oscillation in shear, modulated differential scanning calorimetry, and infrared spectroscopy. Informed temperature application results in the formation of continuous networks at the denaturation temperature, which undergo vitrification at subzero temperatures. In contrast, high-pressure-treated WPs resist physicochemical denaturation, hence preserving the native conformation of secondary and tertiary structures. This was rationalized on the basis of a critical concentration threshold where transfer of water molecules to nonpolar residues in the protein interior is minimized because of low moisture content and restricted molecular mobility. The physical state and morphology of these high-solid preparations were further examined by the combined framework of reduced variables and Williams, Landel, and Ferry equation/free volume theory. Theoretical treatment of experimental observations unveils the dynamic range of the mechanical manifestation of the glass transition region in samples subjected to heat or pressure. In addition to preserving native conformation, WPs subjected to high pressure form glassy systems at parity with the structural functionality of the thermally treated counterparts. © 2012 Wiley Periodicals, Inc.
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