Active food packaging development: rambutan (Nephelium lappaceum L.) peel extract incorporated into starch-protein blend films

Abstract

Natural biopolymers, including carbohydrates, proteins, and fats, have gained significant interest in this emerging phase of a circular economy and sustainable environment. Blending multiple polymers helps overcome their poor mechanical and barrier properties, consequently enhancing their resemblance to commercially used synthetic plastics. This study develops biodegradable active packaging by incorporating rambutan peel extract (RPE) into corn starch-soy protein isolate blend films. Different concentrations of RPE (0%, 1%, 3%, and 5%) were added to the blend films and analysed for their physicochemical, mechanical, barrier, microstructure, and antioxidant properties. The incorporation of RPE produced significantly (p < 0.05) darker films with increased thickness while exhibiting similar (p ≥ 0.05) moisture content and water solubility. The extract significantly reduces (p < 0.05) the light transmittance and develops a more opaque film than the control. Even though the addition of 5% RPE showed a significant (p < 0.05) improvement in tensile strength (6.36 MPa) and flexibility (7.10%), the highest water vapour permeability (1.63 10⁻¹⁰ g m⁻¹ s⁻¹ Pa⁻¹) was recorded. Small voids and a heterogeneous internal structure were observed from the microstructure morphology of the active film in comparison to the smooth and homogeneous structure of the control film. A gradual increase in the RPE concentration has increased the antioxidant activities, including ABTS radical scavenging activity (24.32–77.98%), DPPH radical scavenging activity (11.05–66.75%), and ferric reducing antioxidant power, FRAP (26.41–73.59 mM Fe₂SO₄ per g sample), of the active starch-protein biodegradable films. The starch-protein blend films prepared in this study showed promising potential as a low-cost active biodegradable film material to improve the shelf life and quality of food products.