CONCENTRATION-DEPENDENCE OF THE PROPERTIES OF GELATIN AND IOTA-CARRAGEENAN SYSTEMS AT THE GEL POINT

Iota-carrageenan and gelatin gel properties are studied through the ev olution of the frequency dependence of the storage and the loss moduli during gelation or melting near the critical point at several concent rations. The linear viscoelastic properties at the percolation thresho ld follow a power law G'(omega) proportional to G '' (omega) proportio nal to omega(Delta). The critical point is characterized by tan delta G ''/G' = tan(Delta.pi/2) independently of the frequency and it may be precisely located using the variation at several frequencies of tan d elta versus any parameter controlling the advancement of gelation or m elting (time, temperature or concentration). The effect of concentrati on has been studied and state diagrams [T = f(C)] are drawn for both b iopolymers. A detailed study of Delta versus polymer concentration is carried out: values of Delta in the range 0.72 - 0.36 are obtained and they are compared to published results and discussed.