Dual Modification of Red Lentil Starch: Enhancing Functionality for Environmental and Pharmaceutical Applications

This study explored the dual chemical modification of starch isolated from red lentils (Lens culinaris) to develop a biodegradable polymer with enhanced functionality for multifaceted applications. Native starch was isolated via combined salt–alkali treatment and sequentially modified through epichlorohydrin-mediated crosslinking, followed by cationization using glycidyl trimethylammonium chloride (GTAC). Utilizing a Quality by Design (QbD) strategy through Response Surface Methodology (RSM), the cationization endured fine-tuning to reach an optimal degree of substitution (DS = 0.572) under foremost conditions (GTAC: 2.1 mol, NaOH: 0.09 mol, reaction time: 18 h). Structural and functional characterization using FTIR, XRD, TGA, SEM, and zeta potential analysis confirmed the successful modification, indicating enhanced thermal stability, a transition to a more amorphous structure, and a moderately positive surface charge (+7.24 mV). The dual modified cationic lentil starch (CLS) demonstrated effective flocculation of kaolin suspensions, achieving a transmittance of up to 94%. Additionally, CLS showed significantly improved emulsion stability, maintaining over 70% stability after 24 h, compared to native starch, which dropped below 30%. These results emphasize the promising potential of CLS as an eco-friendly and high-performance alternative to synthetic polymers for water treatment and stabilization of emulsion-based formulations.