Ultrasound-assisted extraction of β-glucans from barley

The effect of operational variables on the ultrasound assisted extraction (UAE) of beta-glucans from barley has been studied. The selected sonication variables were amplitude, time and cycle, and their combination represents different amounts of energy. The RSM Box-Behnken approach has been used to maximize both extraction yield and molecular weight (MW) of extracted beta-glucans. The final results of the UAE reveal that the extraction yield depends on amplitude and especially on time: nevertheless MW decreases with time. The maximum extraction yield (66.1%) is achieved when delivering the maximum amount of energy (962.5 kJ/L), leading at the same time to the lowest MW (269 kDa). A reduction in the intensity of the treatment (energy output of 170 kJ/L) decreases the extraction yield up to 44.3% but increases the beta-glucan MW to 461 kDa. The UAE process slightly improves the extraction yield of beta-glucans and their MW compared to that obtained in a stirred tank extraction (3 h, 55 degrees C and 1000 rpm), the main effect of ultrasounds is related with the reduction of process time and energy consumption (3 min versus 3 h and 170 kJ/L versus 1460 kJ/L), what means a real process intensification, very interesting for the scale-up of the process. (C) 2012 Elsevier Ltd. All rights reserved.