Optimization of ultrasound assisted beta-glucan extraction from barley and its application in a model food

In this study, β-glucan, a functional component of barley, was obtained by ultrasound assisted extraction (UAE) and the process parameters were optimized to maximize both β-glucan recovery and reduced viscosity using Response Surface Methodology (RSM) Box Behnken approach. The selected process variables were ultrasound amplitude (50-90%), extraction time (4-20 min) and flour/solvent ratio (0.05-0.20, w/w). The optimum points were determined as 90% of amplitude, 6 min of extraction time and 0.05 (w/w) of flour/water ratio (F/W) which resulted a β-glucan recovery of 38.15 % and a reduced viscosity of 5388 ml/g. The findings revealed that β-glucan recovery increased and the reduced viscosity decreased with increasing amplitude and time. The effect of pretreatment applied to barley flour was also investigated and found to have a considerable effect on β-glucan recovery, reduced viscosity and gum yield. In addition, UAE were compared with conventional extraction (CE) in terms of physicochemical, rheological, molecular and structural properties as well as energy and time requirements in a detailed characterization study. The UAE process significantly improved the β-glucan recovery, gum yield and water solubility compared to that obtained in CE (3 h, 55 °C and 1000 rpm). It also reduced the process time and energy consumption (6 min versus 3 h and 169 kJ/L versus 8910 kJ/L). However, reduced viscosity and molecular weight (MW) were considerably lower in UAE due to the molecular degradation effect of ultrasound. Lastly, β-glucan was incorporated into simit (a bagel-like product) and the final product was characterized based on the sensorial and physical properties along with starch hydrolyze index (HI), predicted glycemic index (pGI) and dietary fiber content. The results indicated that incorporation of β-glucan in the product formulation improved the dietary fiber proportion and lowered the hydrolyze index and glycemic index. Although simit samples were considered acceptable in terms of physical and sensory properties, it is concluded that there is a need for further improvement of sensory attributes.