RuBisCO-based protein and film from Rumex patience L.: Effects of green extraction and NADES plasticization on structural and functional properties.

Abstract

Growing interest in sustainable food packaging has driven the development of bio-based films from underutilized plant proteins. Rumex patientia L. (edible dock), a perennial leafy plant rich in RuBisCO, represents a promising yet largely untapped source of functional film-forming proteins. This study aimed to develop and characterize RuBisCO-enriched edible films using green extraction techniques and innovative plasticization strategies. Proteins were extracted using classical alkaline extraction (CAE) and ultrasound-assisted extraction (UAE), followed by plasticization with either glycerol or a natural deep eutectic solvent (NADES; choline chloride:glycerol, 1:2 mol/mol). Soy protein and corresponding films served as a reference. Extracted proteins and films were analyzed for physicochemical, structural, and functional properties using FTIR, SEM, XRD, as well as water interaction and antioxidant assays. UAE significantly enhanced protein solubility (83.5 % at pH 9) and reduced particle size (∼590.2 nm), leading to films with improved tensile strength (4.10 MPa), elongation (∼135.78 %), and the lowest water vapor permeability (6.36 × 10-11 g·m/m2·s·Pa). CAE-NADES films exhibited the highest crystallinity and bioactivity, achieving 0.518 mg GAE/g total phenolic content and 37.66 % DPPH radical scavenging activity. XRD analysis revealed that both NADES and classical extraction promoted tighter molecular packing, while ultrasound enhanced matrix flexibility. In contrast, soy protein films showed higher permeability and minimal antioxidant capacity. These results highlight the potential of leaf-derived RuBisCO as a sustainable protein source for multifunctional films. The combined use of UAE and NADES provides a tunable strategy to improve structural integrity, barrier performance, and bioactivity for advanced food packaging applications.