Influence of cassava starch and carnauba wax on physical properties of cashew tree gum-based films

• Films were prepared from cassava starch, cashew tree gum (CTG) and carnauba wax (CW).
• The hydrophobic CW improved water vapor barrier and water resistance of films.
• CW impaired the film transparency because it formed a non-miscible phase.
• The relative proportions of cassava starch and CTG did not affect film properties.

Composite cast films were prepared from different proportions of cashew tree gum (70–85%), cassava starch (15–30%), and carnauba wax (0–15%), according to a simplex-centroid mixture design, and some physical properties were modeled as functions of the mixture components. Water vapor permeability and water solubility were decreased by carnauba wax, indicating that the presence of carnauba wax may be interesting for applications which require good water barrier and resistance. On the other hand, carnauba wax presented plasticizing effect on the composite films, lowering glass transition temperature, and decreasing film strength and stiffness while enhancing elongation. The film opacity was increased as a function of carnauba wax concentrations, which may impair the applicability of emulsion films when a high transparency is required. The relative proportions of cassava starch and cashew tree gum did not present significant effects on the physical properties of the resulting films within the ranges studied, probably because both components are polysaccharides with some similar properties when forming films.

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