Mechanical properties of gels formed by mixtures of mucilage gum (Opuntia ficus indica) and carrageenans

The mechanical properties of gels formed by either mixtures of mucilage gum from Opuntia ficus indica and K-carrageenan or i-carrageenan have been examined using dynamic shear and uniaxial compression measurements. A total polymer concentration of 2% (w/w) was used, the proportion of mucilage gum varying from 0 to 80% (w/w) and KCl or CaCl2 in the range from 12 to 60 mM. For the mixed gels of i-carrageenan and mucilage gum, no enhancement of the mechanical properties with respect to the pure i-carrageenan was observed. For the kappa-carrageenan/mucilage gum system, at an 80/20 ratio and 12 mM KCl, higher gel rigidity than the pure K-carrageenan gels was observed and failure stress and strain increases as mucilage gum concentration increases. A peak in the Young's modulus was also observed for these last conditions suggesting a synergistic interaction. The main feature of the mucilage is to enhance elasticity on the final gels. (C) 2002 Elsevier Science Ltd. All rights reserved.