Ultrasound-assisted extraction of β-glucans from barley

Abstract

The effect of operational variables on the ultrasound assisted extraction (UAE) of β-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 β-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 β-glucan MW to 461 kDa. The UAE process slightly improves the extraction yield of β-glucans and their MW compared to that obtained in a stirred tank extraction (3 h, 55 °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.