Brea Gum (from Cercidium praecox) as a structural support for emulsion-based edible films

Abstract

Brea gum (BG) is an exudate gum obtained from the Cercidium praecox tree. It is an acidic polysaccharide, made up of 75 g/100 g of hydrolysable sugars, such as L-arabinose, D-xylose, D-glucuronic acid and 4-O-methyl-D-glucuronate. The purpose of this study was to investigate the role of BG as a structural agent in the formulation of emulsion based films. Beeswax (BW) and glycerol (Gly) were added as moisture barrier and plasticizer, respectively. Mechanical and optical properties, microstructure and water vapour permeability were studied. The concentration of BW and Gly was ranged from 0 to 40 g/100 g in a dry basis with respect to BG. We found that, regardless the BW concentration, films with 0 g/100 g Gly were too brittle and they could not be handled. In contrast, films with 40 g/100 g Gly were too tacky and gummy, consequently they could not be unpeeled. Only those films with 20 g/100 g Gly (and 0, 20 and 40 g/100 g of BW) were assayed. Increasing BW concentration resulted in better vapour permeability, to the detriment of its mechanical properties; meanwhile it had no influence in colour parameters. BG may be considered to be a structural support for emulsion based films, being 20 g/100 g of Gly the satisfactory amount of plasticizer.