Valorization of mulberry (Rubus glaucus) by-products: ultrasound-assisted extraction of total anthocyanins

In this study, the objective was to establish parameters of optimization of the factors such as solvent concentration, extraction time and liquid-to-solid ratio in ultrasound-assisted extraction (UAE) of total anthocyanins from mulberry by-products. The study sample corresponds to mature fruits that did not comply with the size demanded by the market (by-product). Three independent variables including extraction time (6-74 min), liquid-solid ratio (33-66.16 mL/g), and ethanol concentration (63-96%) were investigated. A rotatable central composite design (CCD) and response surface methodology (RSM) was used to investigate the effect of process variables. The optimum conditions of ultrasound-assisted extraction obtained through response surface methodology were as follow: extraction time, 20 min; liquid to solid ratio, 60:1 mL/g, and ethanol concentration, 90%, allowed to obtain a maximum concentration of 259.66 mg/L. To validate the optimized model, the experimental values were compared with the predicted values to check the adequacy of the model. Ultrasound extraction was 13.60% higher than maceration technique and reduces the time from 24h to 20 minutes. The results show that ultrasonic-assisted extraction as a promising agro-industrial process in the recovery of anthocyanins from mulberry by-products.