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Adhesive properties of wheat gluten after enzymatic hydrolysis or heat treatment - A comparative study
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.ORCID iD: 0000-0002-8348-2273
2012 (English)In: Industrial crops and products (Print), ISSN 0926-6690, Vol. 38, no 1, 139-145 p.Article in journal (Refereed) Published
Abstract [en]

Wheat gluten, among other plant proteins, constitutes an attractive raw material for sustainable alternatives to today's petroleum-based wood adhesives. Nevertheless, the bonding performance, and especially the water resistance, of these plant proteins need to be improved to turn them into competitors equal in merit to today's petroleum-based products. The aim of this study was to investigate if mild hydrolysis or heat treatment of wheat gluten will improve its adhesive properties. Wheat gluten was hydrolyzed with the enzyme Alcalase (degree of hydrolysis 0.3-5.5%), or heat treated at different temperatures (50, 70, and 90 degrees C) and varying time intervals (15 min to 24 h). Alkaline water dispersions of these modified wheat gluten samples were used as adhesives to bond together wood substrates of beech at a press temperature of 110 degrees C and a press time of 15 min. The tensile shear strengths of the substrates were measured for comparison of bond strength and resistance to cold water. The substrates were evaluated according to a slightly modified version of the European Standard EN 204. Lower levels of hydrolysis (0.3-0.6%) and most of the heat treatments at 90 degrees C resulted in improved bond strength and water resistance. Nevertheless, the adhesive properties, especially the water resistance, need to be further improved to fulfill today's requirements for wood adhesives.

Place, publisher, year, edition, pages
2012. Vol. 38, no 1, 139-145 p.
Keyword [en]
Wood adhesives, Wheat gluten, Enzymatic hydrolysis, Heat treatment, Plant protein, Mechanical properties
National Category
Agricultural Sciences Biological Sciences
URN: urn:nbn:se:kth:diva-94037DOI: 10.1016/j.indcrop.2012.01.021ISI: 000302433400021ScopusID: 2-s2.0-84857023182OAI: diva2:525231
QC 20120507Available from: 2012-05-07 Created: 2012-05-07 Last updated: 2012-05-14Bibliographically approved
In thesis
1. Exploring the Wood Adhesive Performance of Wheat Gluten
Open this publication in new window or tab >>Exploring the Wood Adhesive Performance of Wheat Gluten
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The increasing environmental concern has reawakened an interest in materials based on renewable resources as replacement for petroleum-based materials. The main objective of this thesis was to explore plant proteins, more specifically wheat gluten, as a binder in wood adhesives intended for typical solid wood applications such as furniture and flooring.

Alkaline and acidic dispersions of wheat gluten were used as wood adhesives to bond together beech wood substrates. Soy protein isolate was used as a reference. The tensile shear strengths of the substrates were measured for comparison of bond strength and resistance to cold water. AFM in colloidal probe mode was used to investigate nanoscale adhesion between cellulose and protein films. Wheat gluten was divided into the two protein classes; glutenins and gliadins, and their adhesive performance was compared with that of wheat gluten. Heat treatment and mild hydrolysis were investigated as means for improving bonding performance of wheat gluten. The treated wheat gluten samples were analysed by SE-HPLC and 13C-NMR to correlate molecular size distribution and structural changes with bonding performance.

Soy protein isolate is superior to wheat gluten, especially in regards to water resistance. However, the bond strength of wheat gluten is improved when starved bond lines are avoided. The AFM analysis reveals higher interfacial adhesion between soy protein isolate and cellulose than between wheat gluten and cellulose. These results partly explain some of the differences in bonding performance between the plant proteins. Soy protein isolate contains more polar amino acid residues than wheat gluten and possibly interacts more strongly with cellulose. Furthermore, the bond performances of wheat gluten and glutenin are similar, while that of gliadin is inferior to the others, especially regarding water resistance. The extent of penetration of the dispersions into the wood material has a large impact on the results. The bonding performance of gliadin is similar to the others when over-penetration of the dispersion into the wood material is avoided. Moreover, the bond strength of the wheat gluten samples heated at 90°C was in general improved compared to that of wheat gluten. A small improvement was also obtained for some of the hydrolyzed wheat gluten samples (degree of hydrolysis: 0-0.6 %). The improvements in bonding performance for the heat treated samples are due to polymerization, while the improvements for the hydrolyzed samples are due to denaturation. The 13C-NMR analysis of the treated samples confirms some degree of denaturation.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. 74 p.
Trita-CHE-Report, ISSN 1654-1081 ; 2012:23
plant protein, wood adhesive, mechanical properties, wheat gluten, soy protein isolate, gliadin, glutenin, adhesion, hydrolysis, heat treatment, AFM
National Category
Polymer Technologies
urn:nbn:se:kth:diva-94883 (URN)978-91-7501-348-0 (ISBN)
Public defence
2012-06-01, Sal K2, Teknikringen 28, KTH, Stockholm, 10:00 (English)
QC 20120514Available from: 2012-05-14 Created: 2012-05-11 Last updated: 2012-05-14Bibliographically approved

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