Process Optimization of Ultrasound-Driven Extraction of Phytochemicals from Litchi (Litchi Chinensis) Peel through Response Surface Analysis

Abstract

This research focuses on a pulsed-mode ultrasound-assisted extraction (PUAE) technique aimed at increasing the extraction of phenolic compounds from litchi (Litchi chinensisSonncv. Shahi) peel. Initially, one factor at a time (OFAT) experiments were performed to determine the optimum particle size and solvent concentration, resulting<250 µm particle size and 50% ethanol solution as the greatest extraction potential. The optimization of three key process parameters ultrasound power, stirring speed, and sonication duration was performed using response surface-based experiments (RSM) integrated with an experimentaldesign named Box–Behnken (BBD). The effects of these variables were evaluated based on five responses:total phenolic content (TPC), total flavonoid content (TFC), DPPH radical scavenging activity (AOX), total condensed tannin (TCT) and ferric reducing antioxidant power (FRAP). The developed regression models had high R² values (over 0.87) alongside non-significant lack-of-fit, ensuring reliability. Most responses were dominated by significant linear effects of ultrasound power and sonication time, while stirring rpm was largely inconsequential. The conditions reached were set at ultrasound power of 599.99 W, stirring of 654.99 rpm, and 15.00 min sonication time which produced values of 97.25 ± 0.96 mg GAE/g TPC, 90.03 ± 1.59 mg QE/g TFC, 85.78 ± 0.06% AOX, 24.69 mg TE/g FRAP, and 64.00 ± 1.02 mg CE/g TCT with an overall desirability of 0.94.High pressure liquid chromatography(HPLC) of the extract was analysed to established the presence of several major phenolic constituents.The study affirms PUAE as a green, efficient,and novel method for valorisingshahilitchi peel for nutraceutical and functional food applications.