Ultrasound-assisted extraction of β-D-glucan from hull-less barley: Assessment of physicochemical and functional properties

The present study was carried out to investigate the effect of ultrasound-assisted extraction (UAE) method on physicochemical and molecular properties of hull-less barley beta-D-glucan. With increasing sonication time, beta-D-glucan flow behavior index (n) and its extraction yield significantly increased while its consistency coefficient and lightness decreased. Sonication time had no significant effect on beta-D-glucan purity, emulsion and foam stabilizing effect and colour. Increasing pH from 5 to 9 significantly enhanced extraction yield, purity, consistency coefficient (k), emulsion stabilizing effect and yellowness of the final product. At higher pHs, flow behavior index (n) and redness and yellowness decreased. With increasing the amplitude, extracted P-D-glucan flow behavior index (n), redness significantly increased. In contrast, beta-D-glucan purity, emulsion stability, consistency coefficient (k) and yellowness decreased as a result of increase in sound amplitude. However, sound amplitude had no significant effect on beta-D-glucan lightness. Models presented in this study were highly significant and the correlation coefficient could be used for optimization of beta-D-glucan extraction from hull-less barley. Considering the importance and desirability of the response variables, the best results were obtained when the sonication time, amplitude and pH were 4.8 min, 50% and 9, respectively. beta-D-Glucans extracted by UAE had lower average molecular weight compared to those extracted by water extraction method. There was no difference between the chemical structures of beta-D-glucans extracted by UAE and conventional method. This means that short time ultrasonic extraction had no effect on chemical structure of beta-D-glucan. These results indicate that UAE method was a very effective tool for extraction of beta-D-glucan as a potential hydrocolloid agent for food industries. (C) 2016 Elsevier B.V. All rights reserved.