Development of sweet potato starch-based thin films to produce biodegradable packaging materials

Abstract

Starch-based bioplastics are widely used due to their renewability, sustainability, and cost-effectiveness. On the other hand, native starch films have some barriers to creating good and effective products because of their excessive water absorption and weak mechanical characteristics. In this study it was developed an acid hydrolyzed, sweet potato starch-based thin film as a biodegradable packaging material, and the physiochemical properties of the acid hydrolyzed thin films were also investigated. The sweet potato starch was extracted, and acid hydrolyzed by HCl for 30, 60, and 90 minutes. The results of Fourier Transform Infrared spectrometry (FTIR) show that increasing the acid reaction time considerably reduces water absorption and that the best acid reaction time is resolved at 60 minutes. Films were prepared through gelatinization, using glycerin as a plasticizer. The thin films were characterized through FTIR, X-ray diffraction (XRD), and thermogravimetric analysis (TGA) tests. The FTIR test results indicate that in acid reaction, moisture absorbance decreases. The water absorption test results showed that after 24 hours, the acid hydrolyzed sweet potato starch films have lower water absorption than the native sweet potato starch thin films, with 26. 39% and 46.88%, respectively. The acid hydrolyzed film will increase the strength to 5.7 MPa and reduce elongation. It is conclusive that acid hydrolyzed starch-based thin films have increased tensile strength and durability due to their lower water absorption. Further, these films are introduced as non-toxic, low-cost, and biodegradable materials for packaging applications.