Characterization of bio-based plastic made from a mixture of Momordica charantia bioactive polysaccharide and choline chloride/glycerol based deep eutectic solvent

Abstract

Momordica charantia bioactive polysaccharide (MCBP) was used as an alternative source for the production of bio-based plastics (BPs) with choline chloride/glycerol-based deep eutectic solvent (DES) as a plasticizer. In this study, MCBP was initially extracted using 0.1 M citric acid at temperature 80 °C for 2 h, precipitated using ethanol, and then lyophilized. Subsequently, seven BPs were prepared: MCBP without plasticizer (MCBP), with 1% (w/w) of glycerol (MCBP-G), or with 1% (w/w) of DES at different choline chloride/glycerol molar ratios (i.e. 1.5:1, 1:1, 1:1.5, 1:2, and 1:3). The properties of these BPs were then investigated. Results showed that the tensile strains, stresses and moduli were in the range of 1.3–13.3%, 4.8–19.1 MPa and 132–2487 MPa, respectively. The melting temperatures were found in the range of 92.6–111.4 °C whereas the moisture absorptions and water vapour transmission rates (WVTR) of BPs were 1.4–6.5% and 3.6–5.4 mg/m2·s, respectively. The results also showed that these BPs exhibited bioactivities, such as microbial inhibitory activity (19.5–32.3 mm), free radical scavenging activity (10.3–18.3%) and ferric reducing antioxidant power (FRAP, 16.1–20.0 mM). In addition, it was observed that using DES as a plasticizer had improved the properties of BP, such as tensile strain (354.7–937.5%), melting temperature (4.6–20.3%), radical scavenging activity (0.6–88.6%), FRAP (0.9–18.7%) and antimicrobial activity (12.3–33.6%) compared to MCBP, due to the fact DES has caused different degrees of plasticization via hydrogen bonds and ionic bonds with the polymer chains, and induced a lower pH condition. Therefore, it was suggested that these BPs with DES could contribute to food preservation properties.