Post-heat treatment effects on alginate films reinforced with carrot pomace-derived cellulose nanofibers for sustainable quick-dissolving applications

This study introduces an innovative and sustainable strategy to combat plastic pollution and promotes a circular economy by transforming carrot juice industry waste into cellulose nanofibers (CNFs). These CNFs are then seamlessly integrated into biodegradable alginate, improving its mechanical strength and water resistance. Furthermore, we present a novel, eco-friendly heat treatment technique for crosslinking the CNFs with alginate matrices, effectively eliminating the need for chemical crosslinkers, and paving the way for more environmentally friendly material solutions. Notably, incorporating 5 wt% CNFs into alginate films, followed by post-heat treatment at 110 °C for 15 min, resulted in a remarkable increase in tensile strength from 6.27 ± 0.81 MPa (Alg) to 9.68 ± 0.63 MPa (Alg_5%CNF_110), representing a 54% improvement in mechanical properties. This heat treatment also significantly enhanced hydrophobicity, as evidenced by the water contact angle increasing from 88.48° ± 2.77° (Alg) to 108.33° ± 5.42° (Alg_5%CNF_110), indicating improved water resistance. The effectiveness of the crosslinking was confirmed by FTIR analysis, which revealed a C = O stretch at 1747 cm⁻¹. Additionally, properties such as moisture content and solubility time were positively influenced by the CNF content and heat treatment. Importantly, all bio-nanocomposite films exhibited excellent compatibility with mammalian NIH 3T3 fibroblast cells, highlighting their safety and biocompatibility. These findings position Alg_CNF bio-nanocomposite films as promising candidates for quick-dissolving applications, supporting sustainable alternatives across various industries including packaging, personal care products, and biomedical uses.