Isolation of Galactoglucomannan from Apple Hemicellulosic Polysaccharides with Binding Capacity to Cellulose

The hemicellulose fraction which is soluble in 24% KOH solution (HC-II) from the cell-walls of apple flesh contained a small amount of galactoglucomannan in addition to a large amount of xyloglucan. A crude galactoglucomannan was isolated from the HC-II fraction with binding capacity to cellulose microfibrils. The crude galactoglucomannan fraction was treated with xyloglucanase to remove concomitant xyloglucan, followed by DEAE-Sephadex A-25 chromatography to give a purified galactoglucomannan fraction. Sugar composition analysis showed that the purified galactoglucomannan fraction consisted of Man, Glc and Gal in the molar ratio of 5.7:3.0:1.1. Methylation analysis suggested that a galactoglucomannan present in apple flesh had β-(1→4)-linked Glc and Man residues, some of which were branched at the O-6 position with Gal residues.