Fractionation and partial characterization of non-pectic polysaccharides from yellow mustard mucilage

A polysaccharide fraction was isolated from yellow mustard mucilage using pectinase hydrolysis and ammonium sulphate precipitation. Results indicated that ammonium sulphate precipitation produced a material with more glucose and less uronic acid compared to ethanol precipitation. Chemical, structural and rheological properties of the isolated fraction were investigated. Chemical analysis revealed that this material was mainly composed of glucose (61.1%); however, other sugars were also found, including galactose (13.8%), rhamnose (4.5%), mannose (13.1%) and xylose (7.5%). It also contained 6.9% of uronic acid. Methylation analysis indicated that this polysaccharide fraction consisted mainly of a β-1,4 linked glucosyl backbone. Rheological tests showed that the polysaccharide exhibited strong shear-thinning flow behaviour and weak gel structure. When the aqueous weak gel solution was subjected to an acid environment, the gel structure became stronger compared to more neutral conditions. This polysaccharide exhibited thermal stability over the temperature range from 5 to 90 °C.