Effects of Extraction Methods on Physicochemical Properties and Viscosity of Polysaccharides from Orange Peel

In order to take full advantage of the orange peel resource, polysaccharides were extracted from orange peel by hot buffer, chelating agent, dilute alkaline, concentrated alkaline, acid and enzyme extraction, respectively. The physicochemical properties and viscosity of the six polysaccharides were determined. The results showed that the six polysaccharides were mainly consisted of rhamnose, arabinose, galactose and glucose and traces of other monosaccharide. The six polysaccharides exhibited high total carbohydrate (89.74-98.08%), galacturonic acid content (GalA, 8.95-33.16%) and little proteins (<2%). Degree of methoxylation in polysaccharide obtained from orange peel by enzyme extraction and orange peel by acid extraction was higher than the others. They all showed good thermal stability under 84.5 degrees C and non-Newtonian flow behaviors. Polysaccharide obtained from orange peel by hot buffer extraction has higher viscosity than the others at the 0.5% concentration. Polysaccharide obtained from orange peel by dilute alkali extraction appeared the highest viscosity with the increase of concentration, which may be due to the smallest hydrodynamic diameter and the highest rhamnose content.