Effect of Glycerol on Physical and Mechanical Properties of Wheat Starch Edible Films

In this research, edible films were produced using native wheat starch with different concentrations of glycerol (0, 20, 30, 40 and 50% of starch dry weight basis). Starch films were prepared by casting after gelatinization. The effects of glycerol on the microstructure, crystallinity, solubility in water, moisture absorption, water vapor permeability, optical and mechanical properties of the films at 25C and relative humidity range of 11-84% were investigated. The increase of glycerol content led to increase in film solubility, lightness, more compact structures and water absorption at 25C. The lowest water vapor permeabilities were found for the films with 20 and 30% glycerol. Glycerol did not change X-ray patterns of starch films; however, the degree of crystallinity reduced. In general, for all starch films stress at break and Young's modulus decreased and elongation increased when glycerol concentration and/or RH increased. Practical Application The inclusion of glycerol into starch films prepared by casting can increase film solubility, lightness, water absorption and produce more compact structures. Glycerol up to 30% reduced the water vapor permeability of starch films and more glycerol increased this parameter. Glycerol decreased stress at break and Young's modulus of starch films; however, elongation increased. Glycerol is able to improve some mechanical properties of the starch films.