Physicochemical properties of nanocomposite films made from sorghum‐oxidized starch and nanoclay

The aim of this study was to evaluate the incorporation of nanoclay in the polymer matrix of native and oxidized sorghum starches films. The nanocomposite films were prepared by the casting technique and the physicochemical, water vapor barrier, mechanical, and morphological properties, as well the contact angle with water and the distribution of the nanoclay in the film were evaluated. The oxidized starch films showed a higher tensile strength, stiffness, and angle of contact with water, as well as a greater morphological homogeneity on the cross section when compared to native starch films. The nanoclay resulted in a significant (p ≤ 0.05) decrease in tensile strength, elongation, and stiffness in the films. The water vapor permeability was reduced with the addition of nanoclay to the native starch films; however, the oxidized starch film did not change. The nanoclay in the native starch films increased the contact angle from 19.2 to 26.1° at 7.5% of nanoclay. However, in the oxidized starch films the contact angle reduced from 29.1 to 18.3° with 7.5% of nanoclay and increased the presence of microfissures. The sorghum starches and nanoclay films have good potential for use in packaging, due to the good water vapor barrier, morphological properties, and an overall good appearance. The addition of nanoclay in sorghum starch films can contribute to the development of more water‐resistant films to be applied in food with high moisture.