Louis M. Nwokocha

Hydrodynamic and rheological properties of Irvingia gabonensis gum

The polysaccharide component of Irvingia gabonensis endosperm was isolated and its hydrodynamic and rheological properties investigated. The polysaccharide is an arabinogalactan and contains small amounts of rhamnose, galacturonic acid, glucose and glucuronic acid. The polysaccharide displayed typical polyelectrolyte behaviour in solution. The intrinsic viscosity at infinite ionic strength, a measure of the hydrodynamic volume of the uncharged polysaccharide molecule, was obtained as 4.9 dl/g. The macromolecules have a semi flexible backbone with a Smidsrod stiffness parameter of 0.085. The polysaccharide exhibited non-Newtonian behaviour at all the concentrations (0.2% to 3.0% (w/v)) investigated. Cox-Merz plots showed that η(γ˙) and η(ω) were closely superimposable except at low shear rates and higher concentrations, where η>η. The high Mw (1.56 × 10(6)g/mol) and its random coil conformation show I. gabonensis polysaccharide has potential for application as a thickener.

Adhesive Properties of Cyanoethyl Starch

Cassava starch was cyanoethylated to different degrees of substitution (DS) and then used in adhesive preparations. The adhesives were used in bonding wood substrates and the adhesive strength of the bonded substrates was evaluated using a tensometer. The effects of the DS, solids content, pH and moisture on adhesive strength were investigated. The adhesive strength increased with increasing DS; with respect to the percentage solids, it increased to a maximum and then decreased again; with pH, it showed a minimum at a neutral pH; while it decreased with length of exposure to saturated moisture conditions. The experimental data were subjected to regression analysis to find the best fitting models. The results showed that the adhesive strength varied polynomially with DS (R 2 = 0.97), pH (R 2 = 1.0), percentage solids content (R 2 = 0.94), and exponentially with the length of exposure to saturated moisture conditions (R 2 = 0.96). Cyanoethylation significantly enhanced the adhesive property of starch (p < 0.05) and the cyanoethyl starch adhesives were found effective for bonding wood. However, cyanoethyl starch adhesive is not suitable as structural adhesive in a high moisture environment. The performance of cyanoethyl starch adhesive was compared with two commercial adhesive pastes.

Solution Properties of Brachystegia Eurycoma Seed Polysaccharide

Water soluble seed polysaccharides have a variety of applications in the Food Industry. They serve as viscosity modifiers, gelling agents, texturizers, binders and sugar/ice crystal growth inhibitors; polysaccharides from plants such as guar and locust bean are widely applied industrially because of their viscous characteristics. Brachystegia eurycoma belongs to the family Leguminosae. The use of Brachystegia eurycoma is currently limited to local culinary uses despite promising characteristics of the polysaccharide component of the seed; there is very little information on the properties of the polysaccharide which would stimulate expansion in its applications. In this investigation the researchers report on the seed composition, gum yield, molecular characteristics, and effect of temperature and small angle deformation on the properties of the seed polysaccharide.