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Antimicrobial compression-moulded wheat gluten films containing potassium sorbate
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
2012 (English)In: Food Research International, ISSN 0963-9969, E-ISSN 1873-7145, Vol. 45, no 1, 109-115 p.Article in journal (Refereed) Published
Abstract [en]

Antimicrobial glycerol-plasticized wheat gluten (WG) films containing potassium sorbate (PS) were successfully produced by compression moulding; a thermoplastic process involving high temperature and high pressure. Antifungal properties of the films were tested against Aspergillus niger and Fusarium incarnatum by the agar diffusion assay. The results indicated that films containing more than 10 wt.% PS showed antimicrobial activity against A. niger while films containing 2.5 wt.% or more of PS showed antimicrobial activity against F. incarnatum. It was also found that when the film was exposed to an absorbing medium (the agar solution), most of the PS was released, an interesting feature for edible active packaging. Despite the loss, a very promising result was that, without seeding of spores, the films resisted microbial growth for at least one week when the films were left in the agar solution. X-ray diffraction and field emission scanning electron microscopy revealed that the PS crystals were dissolved in the wheat gluten material. In addition to the antimicrobial properties, dynamic mechanical, tensile, PS loss, water vapour transmission rate and oxygen permeability data also indicated that PS acted as a plasticiser in the wheat gluten film.

Place, publisher, year, edition, pages
2012. Vol. 45, no 1, 109-115 p.
Keyword [en]
Wheat gluten, Potassium sorbate, Compression moulding, Antifungal, Mechanical properties, Plasticiser
National Category
Polymer Technologies
Identifiers
URN: urn:nbn:se:kth:diva-92363DOI: 10.1016/j.foodres.2011.10.012ISI: 000300745700015Scopus ID: 2-s2.0-80855132466OAI: oai:DiVA.org:kth-92363DiVA: diva2:516135
Note
QC 20120417Available from: 2012-04-17 Created: 2012-04-02 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Wheat Gluten -Based Materials and Composites: Extrusion, Casting and Antimicrobial Properties
Open this publication in new window or tab >>Wheat Gluten -Based Materials and Composites: Extrusion, Casting and Antimicrobial Properties
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The use of bio-based polymers as packaging materials has gained much attention due to increasing environmental concerns regarding non-biodegradable petroleum-derived plastics. Wheat gluten (WG) is a valuable renewable resource for the production of bio-based materials because of its low price, biodegradability, good film-forming properties and good gas barrier properties under dry conditions. This study presents the processing and development of WG-based materials and composites.

The first part presents a novel approach to obtain high quality WG films in a solvent-free extrusion process. Extrudability of WG was significantly improved by using urea and the films were flexible with remarkable barrier properties. Results indicated that urea-containing films were aggregated/polymerized and contained a considerable amount of b-sheet structure with a high degree of hydrogen bonding.  Adding urea changed the protein structure, and it was found that urea seemed to work as a plasticiser, as observed by the way in which the barrier and mechanical properties changed with increasing urea concentration (Paper I).

In the second part, wheat gluten/montmorillonite (WG/MMT) nanocomposite films were prepared in a solvent-free extrusion process with urea. The oxygen permeability (OP) and water vapor transmission rate (WVTR) of the films were lowered by the use of montmorillonite clay. At the same time, the stiffness of the films increased without any critical loss of extensibility and the thermal stability of the extrudates was improved by the addition of the clay. Results indicated that the clay particles were layered mainly in the plane of the extruded films and the clay existed as individual platelets, intercalated tactoids and agglomerates (Paper II).

The third part describes the development of WG/silica hybrid materials obtained by the sol-gel process. The presence of silica constrained the WG component to such an extent that moisture-induced aggregation/denaturation was small. Results suggested that the constraint came from interactions between the silica and wheat gluten phases, mainly due to hydrogen bond interactions. A substantial improvement in the thermal properties was observed as the silica content increased. It was found that reduction of the moisture diffusivity in the presence of silica can be explained by the geometrical impedance imposed by the interpenetrating silica phase (Paper III).

The fourth part focuses on thermoplastically produced antimicrobial wheat gluten materials. Antimicrobial WG films containing potassium sorbate (PS) were successfully produced by compression moulding. Films containing more than 10 wt.% PS showed antimicrobial activity against Aspergillus niger while films containing 2.5 wt.% or more PS showed antimicrobial activity against Fusarium incarnatum. It was observed that when no seeding with spores was adopted, the PS films, in contrast to the PS-free films, resisted antimicrobial growth for at least one week. It was also found that PS was dissolved in WG films and that when the films were exposed to an agar solution most of the PS was released. In addition to the antimicrobial properties, results also indicated that PS acted as a plasticiser in the WG films (Paper IV).

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. 55 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2013:6
Keyword
wheat gluten, extrusion, urea, montmorillonite, sol-gel process, hybrid materials, casting, compression moulding, potassium sorbate, antifungal, plasticiser, thermal, mechanical and barrier properties.
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-119786 (URN)978-91-7501-637-5 (ISBN)
Public defence
2013-04-12, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20130322

Available from: 2013-03-22 Created: 2013-03-22 Last updated: 2013-04-11Bibliographically approved

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