Ultrasonic-assisted extraction, calcium alginate encapsulation and storage stability of mulberry pomace phenolics

Mulberry pomace (MP) is a rich source of natural phenolic compounds. Ultrasonic-assisted extraction coupled with an orthogonal array design was employed for efficient extraction of the phenolic compounds. The optimized extraction conditions were using a solid (viz. MP) to liquid (75% ethanol, pH 3) ratio of 1: 20, and extracting at 50 degrees C for 90 min with ultrasonic power of 180 W. The total phenolic content (TPC) and DPPH scavenging capacity (EC50) of the extract were 69.914 +/- 0.164 mg GAE/g sample and 0.078 +/- 0.006 mg/mL, respectively. The MP extract (MPE) was subsequently encapsulated by extrusion technique in calcium alginate beads and the TPC and encapsulation efficiency for the lyophilized beads which initially stored in concentrated MPE reached 81.456 +/- 0.333 mg GAE/g dry weight of beads and 43.40% +/- 0.18%, respectively. The in vitro release profiles of phenolic compounds in water from encapsulated wet and lyophilized calcium alginate beads showed prolonged release behavior during 180-min dissolution, which followed Fickian diffusion mechanism. During 30-day storage at 4 degrees C, lyophilized beads showed favorable stability in the TPC, implying that they played a protective role on the encapsulated phenolic compounds. In conclusion, lyophilized calcium alginate beads loaded with MPE could be used as carriers of natural phenolics and nutraceutical ingredients.