Properties of Extruded Vital Wheat Gluten Sheets with Sodium Hydroxide and Salicylic Acid

Abstract

This paper presents a novel approach to improve the barrier and mechanical properties of extruded glycerol-plasticized vital wheat gluten sheets. The sheets were extruded with a single screw extruder at alkaline conditions using 3-5 wt % NaOH. Salicylic acid (SA), known to improve the extrudability of wheat gluten, was also added alone or in combination with NaOH. Oxygen transmission rate and volatile mass measurements, tensile tests, protein solubility, glycerol migration, infrared spectroscopy, and electrophoresis were used to assess the properties of the extrudate. Electrophoresis showed that the gluten/glycerol sheet and the sheet with 3 wt % NaOH and 1 wt % SA contained the same building blocks in terms of proteins and protein subunits, although the protein solubility in these samples was different. The oxygen barrier, at dry conditions, was improved significantly with the addition of NaOH. On the other hand, the addition of salicylic acid yielded poorer barrier properties. The extrudate was placed on a blotting paper and its aging properties were investigated during the first 120 days. It was observed that the extrudate with 3 wt % NaOH had the most suitable combination of properties (low oxygen permeability, large strain at break, and relatively small aging-induced changes in mechanical properties); the reason is probably due to low plasticizer migration and an optimal protein aggregation/polymerization.

Biobased Materials Production from Biodiesel Residuals of Rapeseed

“…Protein polymerization properties have, in several studies, been shown to be the main determinant of tensile properties of gluten materials [5,13]. The present study gave very little evidence of any higher degree of polymerization of the rapeseed proteins in the rapeseed residuals used.…”

“…The most well known of those, being evaluated in a number of studies, is the wheat gluten, a residue from the starch/bioethanol industry and the protein-rich part from wheat after the starch and other carbohydrates have been washed away [11,12]. Gluten residue from the bioethanol industry has a high protein content (around 78%) and is possible to both compression mold and injection mold into materials of relatively high quality in terms of strength and barrier properties [5,13,14]. Examples of other plant proteins that have been reported to have potentials for materials production are soy and corn proteins [8,15,16].…”

“…Most essential for determination of the quality of biomaterials are the composition of the proteins in the plant used and the possibilities of these proteins to polymerize [4][5][6]. Therefore, suitability of proteins, from different types of crops, has to be evaluated according to their usefulness for production of biomaterials for different end-uses.…”

“…Such opportunities will give added value to the rapeseed industry, including the RME production, implicating increased sustainability. To our 2 ISRN Materials Science knowledge, rapeseed residuals have been evaluated in a one study as regards the use of bio-based materials production [7], although a number of other plant proteins have been tested, gluten, soy, and zein being the most commonly used and the most prosperous ones [5,6,8,9].…”

Injection-molded nanocomposites and materials based on wheat gluten

“…wheat gluten is high due to its high molar mass and aggregated structure. Nevertheless, it has been shown, by us and others, that plasticized wheat gluten can be compression molded and extruded into films, troughs and plates [3][4][5][6][7][8]. These methods, however, provide rather limited ways of shaping the material/product into more or less complicated three dimensional (3D) items.…”