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Fig. 1 The chemical structures of alginate, cationic guar gum, and chitosan. G gulosyluronic units, M mannosyluronic units
85 mm). The water evaporated from the molds at room temperature during the course of a few days, resulting in model films of the different polysaccharides. The films were then carefully removed from the petri dishes.
polyelectrolyte titration using a particle charge ana- lyzer. The cationic guar gum powder was dissolved in distilled water to a concentration of 0.5 wt% with the aid of boiling and agitation. Sorbitol was obtained from Sigma–Aldrich and directly dissolved in distilled water to a concentration of 20 wt%. Sorbitol was required as a softener during film casting.
Testing of model polysaccharide films
The thickness of the model films were measured using a Lorentzen & Wettre thickness tester with an accuracy of 0.1 l m. Small ‘‘dog bone’’ shaped test pieces were cut from the polysaccharide model films. The linear area of the test piece was 4 mm in width and 30 mm in length. The tensile tests were performed with an Instron 8872 apparatus, controlled by Blue- hill3 software. The chosen straining speed was 2 mm/ min. The tensile tests were performed at least three
Methods
Preparation of model films from polysaccharides
The solvent casting of the polysaccharide model films were performed similarly to a previously reported method (Rhim 2012). The polysaccharide solution was mixed with sorbitol solution and the mixture was then poured into Teflon-coated petri dishes (diameter
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