Hemicellulose is a heterogeneous polymer of different polysaccharides mainly present in the secondary cell wall. The most common type of polysaccharide is xylan which co-exists with other polysaccharides such as arabinan, galactan and mannan. Arabinan is the second most abundant polysaccharide present in hemicellulose after xylan in most plants. Other polysaccharides are often present in small amounts. The proportions of these polysaccharides differ significantly depending on their source and method of extraction (Chandrakant and Bisaria 1998).

The crystallinity index of hemicellulose is lower than cellulose, primary because of the highly branched structure and presence of acetyl group within the polymer chain. In addition, the degree of polymerization of hemicellulose is between 150-200 monomeric units (Harmsen et al. 2010).