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

- Two ultrasound-assisted extraction methods have been developed for mulberry pulp.
- Anthocyanins and total phenolic compounds have been studied.
- Extraction temperature and solvent composition were the most influential parameters.
- The new methods showed high reproducibility and repeatability.
- The applicability of the methods was evaluated in several mulberry jam samples.

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 °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 °C and 76%) and phenolic compounds (64 °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.