Tensile and water vapour properties of calcium-crosslinked alginate-cashew tree gum films

In this study, sodium alginate films were blended with cashew tree gum (CTG) and immersed in CaCl2 solution. The influence of CTG concentration and immersion time in CaCl2 on tensile properties, water vapour permeability and water solubility (WS) of alginate films was evaluated. Glycerol-plasticized alginate/CTG films were cast on glass plates, which were then immersed in a 2% CaCl2 solution to crosslink alginate. CTG concentration in the film solution and immersion time in CaCl2 bath were varied according to a central composite design. Tensile strength, Young's modulus, WS and water vapour barrier of the films were favoured by higher immersion times in CaCl2 and lower CTG concentrations. The negative CTG effects on such properties have been attributed to competition between the polysaccharides for interactions with calcium ions, reducing crosslinking density and loosening the film structure. On the other hand, this loosening effect resulted in higher film flexibility at higher CTG concentrations.