Properties of Aged Montmorillonite-Wheat Gluten Composite Films
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- 作者：Idoia Olabarrieta ; Mikael Gä ; llstedt ; Iban Ispizua ; Jose-Ramon Sarasua ; and Mikael S. Hedenqvist
- 刊名：Journal of Agricultural and Food Chemistry
- 出版年：2006
- 出版时间：February 22, 2006
- 年：2006
- 卷：54
- 期：4
- 页码：1283 - 1288
- 全文大小：524K
- 年卷期：v.54,no.4(February 22, 2006)
- ISSN：1520-5118
文摘
The properties of new and aged glycerol-plasticized vital wheat gluten films containing 
ges/entities/le.gif">4.5 wt %natural or quaternary ammonium salt modified montmorillonite clay were investigated. The films werecast from pH 4 or pH 11 ethanol/water solutions. The films, aged for ges/entities/le.gif">120 days, were characterizedby tensile testing, X-ray diffraction, and transmission electron microscopy. In addition, water vaporpermeability (11% relative humidity) and the content of volatile components were measured. Thelarge reduction in the water vapor permeability with respect to the pristine polymer suggests that theclay platelets were evenly distributed within the films and oriented preferably with the platelet longaxis 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 thepH 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, thepH 4 and pH 11 film strength and the pH 4 film stiffness increased and the pH 4 film ductility decreasedat the same rate with or without clay. This suggests that the aging was not diffusion rate limited, thatis, that the loss of volatile components or the migration of glycerol or glycerol/wheat gluten phaseseparation was not limited by diffusion kinetics. The aging rate seemed to be determined by slowstructural changes, possibly involving protein denaturation and aggregation processes.Keywords: Wheat gluten; aging; montmorillonite; cast films; tensile properties; water vapor permeability