Characterization and environmental footprint of crosslinked faba bean starch-based ecofilms reinforced with tunicate cellulose nanocrystals

Abstract

The growing demand for sustainable materials has intensified efforts to valorize by-products such as faba bean starch (FBS), a co-product of seed fractionation currently lacking high-value applications. This study investigates the development of ecofilms from crosslinked air classified (65 % starch content) and isolated (95 % starch content) FBS, reinforced with tunicate cellulose nanocrystals (t-CNCs, 0–6 wt% relative to starch dry weight). Isolated FBS films exhibited superior moisture resistance, with an 8.13 % reduction in water vapor permeability (WVP) at 6 wt% t-CNC, while air classified films showed increased WVP upon t-CNC inclusion. Water solubility ranged from 34.35 % to 53.92 %, and the water contact angle decreased slightly due to hydrogen bonding facilitated by surface hydroxyl groups of the starch and t-CNC. Tensile strength (TS) improved to 3.41 MPa in isolated FBS films at 4 wt% t-CNC threshold compared to 2.95 MPa at 4 wt% t-CNC for air FBS classified films, with elongation at break maintained between 20 and 40 % in all the films. SEM analysis revealed increased surface roughness at higher t-CNC concentrations, FTIR confirmed successful component blending, and XRD indicated amorphous film structures. Antimicrobial activity showed efficacy against food spoilage pathogen (E. coli), while thermal stability (97 % weight retention at 150 °C), and a low carbon footprint underscore the films' suitability for sustainable food packaging. These results position crosslinked FBS/t-CNC ecofilms as high-performance, sustainable alternatives to conventional plastics, advancing the development of eco-friendly materials for diverse applications.