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Properties of new and aged montmorillonite-wheat gluten composite films
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
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2006 (English)In: Journal of Agricultural and Food Chemistry, ISSN 0021-8561, E-ISSN 1520-5118, Vol. 54, no 4, 1283-1288 p.Article in journal (Refereed) Published
Abstract [en]

The properties of new and aged glycerol-plasticized vital wheat gluten films containing ≤4.5 wt % natural or quaternary ammonium salt modified montmorillonite clay were investigated. The films were cast from pH 4 or pH 11 ethanol/water solutions. The films, aged for ≤120 days, were characterized by tensile testing, X-ray diffraction, and transmission electron microscopy. In addition, water vapor permeability (11% relative humidity) and the content of volatile components were measured. The large reduction in the water vapor permeability with respect to the pristine polymer suggests that the clay platelets were evenly distributed within the films and oriented preferably with the platelet long axis parallel to the film surface. The film prepared from pH 11 solution containing natural clay was, as revealed by transmission electron microscopy and X-ray diffraction, almost completely exfoliated. This film was consequently also the strongest, the stiffest, and the most brittle and, together with the pH 11 film containing modified clay, it also showed the greatest decrease in water vapor permeability. The large blocking effect of the clay had no effect on the aging kinetics of the films. During aging, the pH 4 and pH 11 film strength and the pH 4 film stiffness increased and the pH 4 film ductility decreased at the same rate with or without clay. This suggests that the aging was not diffusion rate limited, that is, that the loss of volatile components or the migration of glycerol or glycerol/wheat gluten phase separation was not limited by diffusion kinetics. The aging rate seemed to be determined by slow structural changes, possibly involving protein denaturation and aggregation processes.

Place, publisher, year, edition, pages
2006. Vol. 54, no 4, 1283-1288 p.
Keyword [en]
Wheat gluten, aging, montmorillonite, cast films, tensile properties, water vapor permeability
National Category
Chemical Sciences
URN: urn:nbn:se:kth:diva-5130DOI: 10.1021/jf0522614ISI: 000235627800043ScopusID: 2-s2.0-33644905614OAI: diva2:7915
Uppdaterad från submitted till published: 20101013. QC 20101013Available from: 2005-05-18 Created: 2005-05-18 Last updated: 2011-10-19Bibliographically approved
In thesis
1. Strategies to improve the aging, barrier and mechanical properties of chitosan, whey and wheat gluten protein films
Open this publication in new window or tab >>Strategies to improve the aging, barrier and mechanical properties of chitosan, whey and wheat gluten protein films
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Chitosan, Whey Protein Isolate (WPI) and vital wheat gluten (WG) are three biomaterials that have quite promising properties for packaging purposes. They have good film forming properties and good gas barrier properties in dry conditions. Moreover, because they are produced from industrial waste of food processing, they offer an ecological advantage over polymers made from petroleum. However, their physicochemical characteristics still must be improved for them to be of commercial interest for the food packaging industry. The purpose of this work was to study different strategies aiming to improve the water resistance and aging properties of these polymers, which are some of the key disadvantages of these materials.

The produced solution cast chitosan and WPI films were characterised with scanning electron microscopy (SEM), density measurements and thermogravimetry. The water vapour transmission rate was determined at a relative humidity of 11%. In the first part, mechanical properties of solid films and seals were assessed by tensile testing. WG film’s tensile properties and oxygen and water vapour permeabilities were measured as a function of aging time. The changes in the protein structure were determined by infrared spectroscopy and size-exclusion high-performance liquid chromatography and the film structure was revealed by optical and scanning electron microscopy. Gluten-clay nanocomposites were characterised by tensile testing, X-ray diffraction and transmission electron microscopy.

The incorporation of a hydrophobic biodegradable polymer, poly ( ε-caprolactone), PCL, in both chitosan and whey protein, yielded a significant decrease in water vapour transmission rate. It was observed that a certain amount of the PCL particles were ellipsoidal in chitosan and fibrous in WPI. The obtained data also indicated that the particle shape had an important influence in the water vapour transmission rate.

In the second part, the aging properties of WG films, plasticized with glycerol and cast from water/ethanol solutions with pH=4 or pH=11 were investigated. WG films made from alkaline solutions were mechanically more time-stable than the acidic ones, the latter being initially very ductile but turning brittle towards the end of the aging period. The protein solubility measurements indicated that the protein structure of the acidic films was initially significantly less aggregated than the in basic films. During aging the acidic films lost more mass than the basic films through slow evaporation of volatiles (water/ethanol) and through migration of glycerol to the paper support. The oxygen permeability was also lower for the basic films.

In the last part, the properties of new and aged glycerol-plasticized WG films at acidic and basic conditions containing ≤4.5 wt% natural or quaternary-ammonium-salt-modified montmorillonite were studied. Films of WG with montmorillonite were possible to produce by solution casting. The aging rate of acidic and basic films was unaffected by the incorporation of clay. However, the large reduction in water vapour permeability for most systems suggested that the clay sheets were evenly distributed within the films. The film prepared from basic solution and containing natural clay was almost completely exfoliated as revealed by transmission electron microscopy and X-ray diffraction. The best water vapour barrier properties were obtained by using modified clay.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. 68 p.
Trita-FPT-Report, ISSN 1652-2443 ; 2005:14
Chemistry, biodegradable polymers, chitosan, whey protein, wheat gluten, poly(ε-caprolactone), montmorillonite, food packaging, permeability, mechanical properties, aging, pH, solubility, migration, solution casting., Kemi
National Category
Chemical Sciences
urn:nbn:se:kth:diva-208 (URN)91-7178-049-1 (ISBN)
Public defence
2005-05-27, K2, Teknikringen 28, Stockholm, 10:00
QC 20101013Available from: 2005-05-18 Created: 2005-05-18 Last updated: 2010-10-13Bibliographically approved

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Olabarrieta, IdoiaGällstedt, MikaelHedenqvist, Mikael S.
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