| Structural and functional properties of beta-glucan purified from a cereal beta-glucan concentrate which is manufactured by a novel patented technique were investigated. The objective of this thesis is to investigate the fine structure and functional characteristics of cereal beta-glucans while acknowledging the intimate relationship between structure and function from both rheological and physiological perspectives.; Nuclear magnetic resonance (NMR) spectroscopy revealed that the chemical structure of beta-glucan purified from barley fiber concentrate was similar to that reported in the literature. Fine structural NMR investigations elucidated that beta-glucan is associated with phosphate moieties in both oat and barley concentrates (degree of substitution (DS) = 0.011 and 0.005, respectively), thus documenting for the first time that beta-glucan may be associated with a negative charge. The higher prevalence of negatively charged phosphate moieties in oat beta-glucan compared to barley may help to explain the higher solubility of oat beta-glucan (6.6-fold greater than barley beta-glucan at 37°C).; Rheological properties such as flow behavior, viscosity, viscoelasticity and thixotropy of solutions of beta-glucan purifed from barley fiber concentrate and 12 common food gums, alone and in combinations, were characterized using an oscillatory rheological measurements. Pure gums and gum combinations were evaluated at 0.5 and 0.75% (w/w) total gum concentration in aqueous medium, whereas the beta-glucan-gum ratio was kept at 90/10 or 80/20 (w/w). Viscosity synergism was observed for beta-glucan solutions in combination with xanthan, iota-carageenan, and carboxymethyl cellulose. In addition, beta-glucan/xanthan gum blends demonstrated improved shear tolerance, gelling tendency and improved phase stability and viscosity stability (pH 3.5).; To evaluate the ability of cereal beta-glucan to lower serum cholesterol levels in the body, in vitro adsorption of bile acids was chosen as an indicator of physiological functionality. A new quantitative method for determining bile acid adsorption of soluble fibers was developed, which was simpler, faster, and could accommodate higher throughput than conventional methods. beta-Glucan purified from the fiber concentrate adsorbed bile acids significantly (p≤0.5) better than any of the twelve gums studied. This body of work establishes the potential of the beta-glucan concentrate to serve as a cholesterol-lowering food ingredient in addition to being an excellent thickener. |
