Production of edible film from buckwheat starch modified with fatty acids

Food polymers such as proteins, polysaccharides and lipids in the generally recognized as safe (GRAS) class and various plasticizers capable of increasing the flexibility of the resultant polymeric films are employed in the production of edible films. Among the polysaccharides, starch stands out because of its economical advantages. Starch-based films however are generally hygroscopic nature leading to the poor barrier and mechanical properties. In order to improve these properties, several applications such as cross-linking of starch or forming complexes of starch with other natural polymers can be performed. In this study, the film production parameters in the preparation of edible films from buckwheat starch, and amylose-lipid complexes formed by using different fatty acids were optimized. Capric acid and myristic acid were used as fatty acids and sorbitol was used as the plasticizer. The optimal conditions yielding the buckwheat starch and amylose-lipid complex films with desired mechanical properties were determined via the optimization of three different parameters (sorbitol concentration, pH and the temperature of the film forming solution) important in the film preparation. After optimization, the films having superior mechanical properties were characterized in terms of physical, barrier and optical properties. The ALC films were found to be more elastic yet had lower tensile strength when compared to the BS films. The physical, mechanical, optical and barrier properties of the films prepared at optimal conditions were investigated. The tensile strength, elongation at break and elastic modulus of films produced from natural buckwheat starch and modified starch by capric and myristic acid were found to be 0.339, 0.139, 0.08 MPa, 45.62, 99.44, 127.94 % and 0.062, 0.051, 0.0015 MPa, respectively. When the films were evaluated in terms of water vapour permeability, water solubility and moisture content, the water vapour permeability of the films was determined as 0.312, 0.147, 0.196 g mm/m2 h kPa, while the water solubility and moisture contents of the BS and ALC films were not significantly different from each other. As a result, the tensile strength, elastic modulus and water vapour permeability of the modified films were lower than the natural buckwheat starch films but the elongation value was higher.