Optimization of Formulation and Process Parameters for Soy Protein-Based Edible Film Using Response Surface Methodology

Edible film based on soy protein isolate, plasticized with glycerol, has been developed by casting method and effects of formulations and process parameters were studied using response surface methodology. The independent variables selected for study were concentration of soy protein isolate (SPI) (6, 8, 10%), concentration of glycerol (40, 50, 60% of SPI) as plasticizer and pH (8, 9, 10) of film-forming solution. The responses selected for the study were thickness, tensile strength, elongation at break and Young’s modulus. The three optimized combinations were obtained using the criteria of maximum tensile strength and elongation at break but minimum thickness and Young’s modulus. These optimized combinations were further used in the study of properties of edible film like moisture content, oxygen permeability and water vapor permeability The best combinations of variables for selected response functions were obtained by keeping SPI concentration constant at 8.65% along with plasticizer concentration of 60% and pH 9.0. The evaluation of effect of optimized formulations on properties of edible film showed that SPI decreased the moisture content and oxygen permeability while it increased water vapor permeability.