The phase behaviors of alginate/xanthan mixtures and their influence on the critical gelation of alginate induced by Ca2+ ions were investigated.At a fixed concentration of alginate (0.5 wt%) and with increasing xanthan concentration

the mixtures exhibited compatible

phase separating and liquid crystalline behaviors.The formation of liquid crystals was found to occur at much lower xanthan concentrations in mixtures than that in pure xanthan solution

suggesting that the presence of alginate promoted the formation of xanthan liquid crystals.This was attributed to the increase in the effective concentration of xanthan as a result of segregative phase separation of alginate/xanthan.Via glucono--lactone (GDL)-induced in situ release of Ca2+ from Ca-EDTA

the viscoelastic properties of alginate/xanthan mixtures at different levels of Ca2+ (f =[Ca2+]/[COO-])were measured.Analysis by the Winter-Chambon criteria showed that the critical gel point (fgel) decreased with increasing xanthan concentration.Accompanying phase separation

fgel decreased dramatically while it turned to increase in the liquid crystalline region.Comparison of the relaxation critical exponents obtained from the Winter-Chambon method and relaxation modulus suggested that the addition of xanthan led to the loss of structural self-similarity for alginate gels at the critical points.Phase separation resulted in a more compact critical gel structure whereas liquid crystalline formation made it relatively looser.