Optimization of the ultrasound-assisted extraction of anthocyanins and total phenolic compounds in mulberry (Morus nigra) pulp

New ultrasound-assisted extraction methods for the determination of anthocyanins and total phenolic compounds present in mulberries have been developed. Several extraction variables, including methanol composition (50-100%), temperature (10-70 degrees C), ultrasound amplitude (30-70%), cycle (0.2-0.7 s), solvent pH (3-7) and solvent-solid ratio (10:1.5-20:1.5) were optimized. A Box-Behnken design in conjunction with a response surface methodology was employed to optimize the conditions for the maximum response based on 54 different experiments. Two response variables were considered: total anthocyanins and total phenolic compounds. Extraction temperature and solvent composition were found to be the most influential parameters for anthocyanins (48 degrees C and 76%) and phenolic compounds (64 degrees C and 61%). The developed methods showed high reproducibility and repeatability (RSD < 5%). Finally, the new methods were successfully applied to real samples in order to investigate the presence of anthocyanins and total phenolic compounds in several mulberry jams. (C) 2016 Elsevier Ltd. All rights reserved.