Fabrication and Characterization of Sweet Potato Starch-based Bioplastics Plasticized with Glycerol

Background and Objective: Poor biodegradability and the contamination risk of petrochemical-based plastics encouraged the utilization of renewable resources to replace them due to their inexpensive, renewable, biodegradable and compostable properties.This study aimed to investigate the utilization of sweet potato sourced from Indonesia as a base material of bioplastic and its characteristics for food packaging application.Materials and Methods: Starch was extracted from sweet potato and bioplastics was prepared by mixing starch with glycerol using different starch:glycerol w/w ratio (2.5:1, 2.75:1, 3:1 and 3.5:1).Intermolecular interactions and microstructure of bioplastics were assessed by using FTIR and SEM, respectively.The physical and mechanical properties were evaluated by measuring the density, tensile strength and elongation at break.The relative hydrophobicity was examined by measuring the water contact angle.The biodegradability was also investigated with the aid of enzymatic degradation by microbes.Results: Microstructure of bioplastics showed the incomplete gelatinization with the increase of starch:glycerol ratio indicated by the visible inhomogeneous granules.FTIR spectra exhibited that the intermolecular interaction in bioplastics occurred through C-O-H, O-H, C-H aliphatic and C=O groups.Mechanical properties evaluation showed that bioplastic with 3.5:1 (starch:glycerol) ratio exhibited the highest tensile strength of 2.57 MPa with the lowest elongation of 6.27%.Bioplastic with 3.5:1 (starch:glycerol) ratio also showed the highest density and contact angle of 1.66 g cmG 3 and 50.1E, respectively.The fastest enzymatic degradation showed by the highest microbial growth was presented by bioplastic with 3.5:1 (starch:glycerol) ratio as well.Conclusion: Bioplastic with the highest sweet potato starch:glycerol ratio showed the most excellent physical, mechanical and biodegradability properties.