Effect of the addition of soy lecithin and Yucca schidigera extract on the properties of gelatin and glycerol based biodegradable films

Gelatin-based films containing soy lecithin or Yucca schidigera extract and glycerol as plasticizer were produced by casting and characterized for their mechanical properties, water vapor permeability (WVP), water solubility, opacity and morphology. The addition of glycerol reduced the tensile strength, with a difference of ~ 68% between the values for the minimum and maximum concentrations evaluated, both for the plasticizer and the surfactant. Elongation values reached 52% and 40%, for films containing yucca extract and lecithin, respectively, when higher amounts of plasticizer and surfactant were added. Lower values of WVP were obtained when the intermediate concentration of glycerol (20 g plasticizer/100 g protein) was used, reaching 0.14 and 0.15 g mm/m² h kPa, respectively, for films containing yucca extract and lecithin. The solubility was not affected by adding plasticizer and / or surfactants. The morphologies of the inner sections of the films, regardless of type of surfactant used, were compact, without pores or phase separation, indicating efficient incorporation of the compounds added to the protein matrix.