Bio-based plastic films prepared from potato peels using mild acid hydrolysis followed by plasticization with a polyglycerol

Abstract

Non-biodegradable, petroleum-derived polymers are widely used for packaging applications despite their negative impact on the environment. This scenario has motivated the development of new alternatives that follow the circular economy concept. Potato peel (PoP) is the main byproduct of the industrial processing of potatoes and is rich in starch. In this work, PoP was hydrolyzed in a mild acid medium, gelatinized in different amounts of one of two plasticizers, glycerol (G) or polyglycerol-3 (G3), and films were obtained by casting followed by compression molding. The results indicate that G3-plasticized films presented higher thermal resistance and reduced water vapor permeability than the G-plasticized PoP films. The mechanical properties of the G3-plasticized films were also improved with respect to G-plasticized films, reaching an elastic modulus of 432 MPa, a tensile strength of 12.7 MPa, and an elongation of 18.4 % when using 20 wt.% of G3 plasticizer. Besides, G3-plasticized films presented higher water solubility (30–45 %) than G-plasticized ones (18–25 %). The suitability of the films prepared with 20 wt.% of G3 as packaging for dry foods was evaluated by measuring the total migration of its components in the Tenax food simulant and its oxygen permeability. The migration results (8.6 mg/dm2) comply with the current regulation for food contact materials. Nevertheless, the oxygen permeability (5.5 × 103 cm3 μm m−² day-1 kPa−1) was unsuitable for long-term protection of food susceptible to oxidation, and for this reason, the developed materials would be appropriate for packaging of dry food where the oxygen barrier is not fundamental.