Dynamic rheological properties of Yam starch/hectorite composite gels

The rheological properties of composite gels of starch extracted from Yam roots (Discorea sp) and hectorite (a mineral clay belonging to the smectite group) were studied in aqueous solutions as a function of hectorite concentration. The elastic (G') and viscous (G") moduli of the composite gels were dependent on the clay content, and for all samples G' was greater than G". Composite gels with clay contents of < 30% presented higher G', G" and viscosities vertical bar eta*vertical bar when compared with pure starch gel, while those with a content of 50% showed lower values. The addition of hectorite significantly inhibited the creeping properties in relation to pure starch at 25 degrees C but, after heating/cooling cycles between 25 and 85 degrees C, this effect was not observed and the composite gel showed similar behavior to that of pure starch. (c) 2005 Society of Chemical Industry.