Evaluation of extrusion-modified fenugreek gum

The present study was carried out to investigate the molecular mass distribution, hydration, and emulsifying properties of extrusion-modified fenugreek gum. Fenugreek gum was extruded in a twin-screw extruder with four different zone 5 barrel temperatures (105, 120, 135, and 150 degrees C). To minimize the reduction in molecular weight of fenugreek gum during the extrusion process, an exit die was not used. High performance size exclusion chromatography revealed that extrusion cooking slightly changed the molecular mass distribution of the gum. Hydration properties of the gum, such as water dis-persibility, water solubility, water hydration viscosity, and water absorption rate, were significantly improved after extrusion cooking. The results suggested that extrusion processing of fenugreek gum could lead to some changes in the structure and functional groups, including disruption of the cell-wall structures and unfolding of the polysaccharide molecules, which could lead to the exposure of functional groups, such as hydrophilic groups, from inside, thereby improving the hydration properties. However, the extrusion process did not significantly affect the water holding capacity of the gum, nor significantly influence the emulsion capacity and stability of the gum. On the other hand, the extrusion process did noticeably remove the unpleasant flavor associated with the original fenugreek gum. (C) 2010 Published by Elsevier Ltd.