Kinetic models and process parameters for ultrasound-assisted extraction of water-soluble components and polysaccharides from a medicinal fungus

Abstract

This study was on the kinetics and process parameters for ultrasound-assisted extraction (UAE) of water-soluble components and polysaccharides (PS) from the dry mycelium of a medicinal fungus, Cordyceps sinensis Cs-HK1. Four process variables (factors) were evaluated at different levels, ultrasound intensity (2.44–44.1W/cm2), temperature (40–70°C), solid particle size (156.5–750μm), and solid-to-liquid ratio (1/30–1/70g/mL). The experimental data of yields versus time in most cases were fitted closely to two empirical kinetic models for solid–liquid extraction, parabolic diffusion equation (y=yo+y1t1/2) and power law (y=βtn) with high correlation coefficients (R2) of 0.95–0.99 for total extract yield, and 0.90–0.96 for PS yield. The PS yield was increased more significantly than the total extract yield with the ultrasound intensity. Reducing the particle size and increasing the extraction temperature led to a higher yield and extraction rate; increasing the solid-to-liquid ratio (or decreasing the liquid volume) increased the PS yield and extraction rate but had little influence on the total extract. Significant correlations were found between extraction rate (dy/dt) and ultrasound power density (P/V), and between extract yield (y) and energy density (Pt/V). The kinetic and process parameters are useful for rational design and efficient operation of UAE processes.