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Freeze-Dried Wheat Gluten-Based Foams
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents wheat gluten foams as an alternative to the available commercialfoams. Polymeric foams, like all plastics, are mostly made from petroleum, and this isaffecting the environment negatively with the emission of greenhouse gases and generation oflandfills. During the past decades, there has been a drive to replace petroleum-based plasticswith alternatives made from renewable resources. Wheat gluten has interesting and promisingproperties as an alternative resource. As a large by-product in Europe from the biofuelindustry it is largely available and at a low price.In order to develop an insulation material based on this renewable resource, foammaterials have been made by freeze-drying frozen mixtures consisting of either acommercially available wheat gluten powder or various protein rich fractions of gliadins orglutenins extracted from the commercial powder. Some of the foams were further modifiedwith the addition of glycerol as plasticizer or bacterial cellulose as a reinforcing fiber. Theresulting cellular structure was shown to depend on the initial gluten concentration, and thefraction and type of additive used. The wheat gluten foam materials contained mainly an openpore structure with average pore diameters ranging from 20 to 70 μm.The addition of glycerol and/or bacterial cellulose changed the foam structure, theprotein structure and the mechanical properties. The addition of 20 wt.% glycerol wassufficient to plasticize the foam and to achieve a low modulus and a high strain recovery, butwith glycerol the average pores size increased due to the difference in freezing conditions.The bacterial cellulose gave a small and insignificant increase in stiffness and also a moreuniform cell structure. In addition, the glycerol-containing samples had a more polymerizedprotein structure, whereas the foams containing fibers had a lower degree of polymerization.Foams made from a glutenin rich fraction were much stiffer and stronger than gliadinrich foams. The glutenin rich foams had a higher degree of polymerization than the latter,foam the relatively mild heat treatment.The gluten foams were promising as insulation materials. The thermal conductivityvalues were 0.04-0.05 (W/m⋅°C), and were close to that of commercially available closed cellpolystyrene and polyurethane foams, that both have values at ca. 0.03 (W/m⋅°C).The wheat gluten foams showed also promising combustion properties with longignition times, no material dripping and a large content of residual char. The glycerolcontainingfoam however, exhibited a more rigorous bubbling and a larger flame.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , 73 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2012:1
Keyword [en]
Foams, Wheat gluten, Glutenin, Gliadin, Renewable, Freeze-drying, Pore structure, Baceterial cellulose, Glycerol, Mechanical properties, Thermal conductivity, Combustion properties
National Category
Polymer Technologies
Identifiers
URN: urn:nbn:se:kth:diva-51511ISBN: 978-91-7501-205-6 (print)OAI: oai:DiVA.org:kth-51511DiVA: diva2:464374
Public defence
2012-01-19, F3, Lindstedtsvägen 26, KTH, Stcokholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20111220Available from: 2011-12-20 Created: 2011-12-13 Last updated: 2011-12-20Bibliographically approved
List of papers
1. Novel Foams Based on Freeze-Dried Renewable Vital Wheat Gluten
Open this publication in new window or tab >>Novel Foams Based on Freeze-Dried Renewable Vital Wheat Gluten
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2010 (English)In: Macromolecular materials and engineering (Print), ISSN 1438-7492, E-ISSN 1439-2054, Vol. 295, no 9, 796-801 p.Article in journal (Refereed) Published
Abstract [en]

A new way of producing rigid or semi-rigid foams from vital wheat gluten using a freeze-drying process is reported. Water/gluten-based mixtures were frozen and freeze-dried. Different foam structures were obtained by varying the mixing process and wheat gluten concentration, or by adding glycerol or bacterial cellulose nanofibers. MIP revealed that the foams had mainly an open porosity peaking at 93%. The average pore diameter ranged between 20 and 73 mm; the sample with the highest wheat gluten concentration and no plasticizer had the smallest pores. Immersion tests with limonene revealed that the foams rapidly soaked up the liquid. An especially interesting feature of the low-wheat-concentration foams was the "in situ'' created soft-top-rigid-bottom foams.

Keyword
fibers, foams, glycerol, pore structure, wheat gluten
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-26297 (URN)10.1002/mame.201000049 (DOI)000282742000002 ()2-s2.0-77956919539 (Scopus ID)
Note
QC 20101123Available from: 2010-11-23 Created: 2010-11-21 Last updated: 2017-12-12Bibliographically approved
2. Mechanical Properties and Network Structure of Wheat Gluten Foams
Open this publication in new window or tab >>Mechanical Properties and Network Structure of Wheat Gluten Foams
2011 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 12, no 5, 1707-1715 p.Article in journal (Refereed) Published
Abstract [en]

This Article reports the influence of the protein network structure on the mechanical properties of foams produced from commercial wheat gluten using freeze-drying. Foams were produced from alkaline aqueous solutions at various gluten concentrations with or without glycerol, modified with bacterial cellulose nanosized fibers, or both. The results showed that 20 wt % glycerol was sufficient for plasticization, yielding foams with low modulus and high strain recovery. It was found that when fibers were mixed into the foams, a small but insignificant increase in elastic modulus was achieved, and the foam structure became more homogeneous. SEM indicated that the compatibility between the fibers and the matrix was good, with fibers acting as bridges in the cell walls. IR spectroscopy and SE-HPLC revealed a relatively low degree of aggregation, which was highest in the presence of glycerol. Confocal laser scanning microscopy revealed distinct differences in HMW-glutenin subunits and gliadin distributions for all of the different samples.

Keyword
FUNCTIONAL-PROPERTIES, Protein-Composition, STORAGE, REACTIVITY
National Category
Medical Biotechnology (with a focus on Cell Biology (including Stem Cell Biology), Molecular Biology, Microbiology, Biochemistry or Biopharmacy) Cell and Molecular Biology
Identifiers
urn:nbn:se:kth:diva-33985 (URN)10.1021/bm200067f (DOI)000290246400035 ()2-s2.0-79955859873 (Scopus ID)
Note

QS 20110523

Available from: 2011-05-23 Created: 2011-05-23 Last updated: 2017-12-11Bibliographically approved
3. Thermal Conductivity and Combustion Properties of Wheat Gluten Foams
Open this publication in new window or tab >>Thermal Conductivity and Combustion Properties of Wheat Gluten Foams
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2012 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 4, no 3, 1629-1635 p.Article in journal (Refereed) Published
Abstract [en]

Freeze-dried wheat gluten foams were evaluated with respect to their thermal and fire-retardant properties, which are important for insulation applications. The thermal properties were assessed by differential scanning calorimetry, the laser flash method and a hot plate method. The unplasticised foam showed a similar specific heat capacity, a lower thermal diffusivity and a slightly higher thermal conductivity than conventional rigid polystyrene and polyurethane insulation foams. Interestingly, the thermal conductivity was similar to that of closed cell polyethylene and glass-wool insulation materials. Cone calorimetry showed that, compared to a polyurethane foam, both unplasticised and glycerol-plasticised foams had a significantly longer time to ignition, a lower effective heat of combustion and a higher char content. Overall, the unplasticised foam showed better fire-proof properties than the plasticized foam. The UL 94 test revealed that the unplasticised foam did not drip (form droplets of low viscous material) and, although the burning times varied, self-extinguished after flame removal. To conclude both the insulation and fire-retardant properties were very promising for the wheat gluten foam.

Keyword
combustion, foam, freeze-drying; glycerol, thermal conductivity, wheat gluten
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-52889 (URN)10.1021/am2017877 (DOI)000301968400066 ()22332837 (PubMedID)2-s2.0-84859149208 (Scopus ID)
Note
QC 20120420. Updated from manuscript to article in journalAvailable from: 2011-12-20 Created: 2011-12-20 Last updated: 2017-12-08Bibliographically approved
4. Freeze-dried forms made from wheat glutenin- and gliadin-rich fractions
Open this publication in new window or tab >>Freeze-dried forms made from wheat glutenin- and gliadin-rich fractions
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(English)Manuscript (preprint) (Other academic)
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-52894 (URN)
Note
QS 2011Available from: 2011-12-20 Created: 2011-12-20 Last updated: 2011-12-20Bibliographically approved

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