Development of natural binders based on agricultural by-products to be applied in the landscaping industry

An alkaline extraction method was applied to extract polysaccharides from agricultural by-products: wheat bran (WB), corn fiber (CF), and okara, in order to substitute psyllium in novel binders. Physicochemical and molecular characterizations indicated WB had better gelling potentials than CF and okara, with a higher molecular weight (MW), higher intrinsic viscosities (IV), and better viscoelastic properties. Results from extrusion process showed WB extrudates had a great increase (more than 100%) in soluble dietary fiber (SDF) content, as well as higher apparent viscosities and MW after extrusion, especially for alkaline-pretreated samples. A rainfall simulation test (RST) approach was applied to evaluate the rainfall-erosion resistance capability of modified binders and compare them to psyllium-based formulas. Fly ash addition (2%) could greatly reduce the solid loss (SL) in RST. WB and modified WB samples did show much better SL results than CF and okara, although they did not achieve the level of psyllium-based binders. Yellow mustard gum (YMG) was also tested in RST and exhibited excellent binding potentials, which had similar SL results to the control and was even better with fly ash added.