Isolation and functional properties of hemicelluloses from oil palm trunks

Approximately 80% (dry weight) of the total hemicelluloses (xylan) was extracted from oil palm trunks (opt). analysis of opt gave the following composition (dry basis): 42%-45% cellulose,26%-29% hemicelluloses and 16%-18% lignin. optimisation of the aqueous extraction was done using the following parameters: 3.0 m alkali concentration,40°c temperature,4 hr soaking time,50 g sample with <0.32 mm fibre/dust sieve size. extracted hemicelluloses were found to have a higher quantity of hemicellulose a (50%) as compared to hemicellulose b (30%). xylose was found to be the major sugar in each of the fractions,with glucose,arabinose and mannose as minor constituents. the carbohydrate composition of the hemicellulose fraction consisted of xylan,to which other carbohydrates were attached. it was found that hemicellulose b had a higher molecular weight than hemicellulose a,while the intrinsic viscosity for both hemicelluloses was in the range of 0.6-0.7 dl g-1. both hemicelluloses were not completely soluble in water at elevated temperature,and their water-holding capacity was less than 10%. opt hemicelluloses exhibited pseudoplastic flow behaviour ('shear thinning') and were affected by shear rate and temperature. the extracted hemicelluloses also had a low digestibility using xylanase enzyme.