Frequency dependence of viscoelastic properties of some physical gels near the gel point

The sol-gel and gel-sol transitions of three biopolymer gelling systems (gelatin, iota-carrageenan and xanthan-carob) have been studied by dynamic measurements. At the gel point a power law dependence of the storage (G') and loss (G”) moduli on frequency is observed, with an exponent varying from 0.5 to 0.65. The variation of log(tg^δ = G”/G') versus the gelation (or melting) parameter (time or temperature) at different frequencies leads to a precise determination of the gel point.