Elucidation of the structural changes of sesame hull hemicelluloses during roasting

Abstract

In this investigation, the hemicellulose fractions were isolated from sesame hulls before and after roasting at 160 °C, 180 °C, 200 °C, and 220 °C. The structural properties of the hemicelluloses were comparatively investigated by analytical techniques including FT-IR, sugar compositions analysis, molecular weight analysis, thermal analysis, and NMR. Roasting at temperatures from 180 to 220 °C resulted in higher yields of hemicelluloses subsequently isolated from sesame hulls by the alkaline method. The results of sugar analysis and average molecular weight analysis of the hull hemicelluloses revealed that the side chain sugar units such as arabinose and rhamnose of the hemicelluloses are more easily degraded after roasting during the roasting. That the main chains of hemicelluloses in the cell wall of sesame seed hulls did not change significantly. The investigation provides new information about the mechanisms of the structural changes that occur in sesame hull hemicelluloses during roasting.

Keywords: Hemicelluloses; Roasting; Sesame hull; Structure.