Formulation and Characterization of Film Based on Gum Exudates from Brea Tree (Cercidium praecox)

Abstract

In the present study, films and coatings for food applications based on a gum exudate from Brea tree (Cercidium praecox) were formulated and the influence of plasticizer content on their functional properties was evaluated. Brea gum is a renewable resource available in semi-desert areas, extracted by native people. Films were produced by casting method and characterized through water vapour permeability, mechanical (tensile strength and elongation at break), morphological and optical properties. Glycerol was used as plasticizer. Brea gum films presented good visual aspect, transparency and amber colour. Microscopic observation showed a dense and homogeneous structure. Film wettability increased with glycerol content due to hydrophilic nature of the plasticizer. Solubility of films in water increased with temperature. Water sorption isotherms of films at 25 °C showed that at high aw (above 0.50), the film matrix swells altering its structure and properties. Water vapour permeability remained practically constant up to 20% of glycerol content and then increases linearly with the plasticizer. The addition of glycerol decreased the opacity and tensile strength. The best film properties were obtained at 20% of glycerol concentration.