DYNAMICS DESCRIPTION AND THERMODYNAMICS ANALYSIS OF POLYSACCHARIDES EXTRACTION PROCESS FROM FOXTAIL MILLET

Abstract

Polysaccharides was extracted from foxtail millet using hot water at the appropriate agitation rate and liquid to material ratio. The changing situations of polysaccharides mass concentration in the extraction solution with the extraction temperature and extraction time were measured. The experimental data obtained were fitted with the second-order dynamic model; the dynamic and thermodynamic parameters were calculated and analyzed. The results showed that the higher the extraction temperature, the shorter the time needed to reach the extraction equilibrium and the higher the polysaccharides equilibrium mass concentration. The extraction process of polysaccharides could be described with the second-order dynamic model. The apparent activation energy value was 44.34 kJ·mol-1. When the extraction temperature increased from 323 to 363 K, the half-life period value was shortened from 33.4 to 6.2 min, and the internal diffusion coefficient increased from 2.43×10-9 to 1.36×10-8 m2·min-1. The enthalpy value and entropy value of the extraction process was 25.92 and 100.06 J·mol-1·K-1 respectively, and the Gibbs free energy value were all less than zero, indicating that the extraction process was an endothermic, entropy increasing, spontaneous and irreversible process. Increasing the temperature was conducive to the process.

Keywords

• foxtail millet
• polysaccharides
• extraction
• model
• dynamics
• thermodynamics