Rice Straw Based Thickening Agent for Dysphagia Supplements

The increasing prevalence of dysphagia among elderly and neurologically impaired populations highlights the urgent need for safe and stable texture-modified diets. Starch, the conventional thickening agent, is prone to rapid enzymatic breakdown by salivary amylase, resulting in compromised viscosity and safety risks during swallowing. Carboxymethyl cellulose (CMC), a cellulose derivative, offers superior viscosity stability and resistance to enzymatic degradation. This study aimed to synthesize CMC from underutilized agricultural waste, namely rice straw, and evaluate its potential as a sustainable thickening agent for dysphagia supplements in comparison with commercial pharmaceutical-grade CMC. Cellulose was extracted from rice straw, carboxymethylated, and incorporated into supplement formulations. The products were characterized using Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and rheological analysis with rotational and shear rheometry. Rice straw-derived CMC achieved a degree of substitution (DS) of 0.79, while commercial CMC displayed a higher DS of 1.3. Both types of CMC resisted amylase-induced degradation, in contrast to starch solutions, which exhibited a loss of more than 97% in viscosity. Rheological results confirmed pseudoplastic behavior; commercial CMC showed higher viscosity (1460 cP, honey-like), whereas rice straw CMC demonstrated lower but more stable viscosity (268 cP, nectar-like). The novelty of this research lies in valorizing rice straw, an abundant agricultural residue, into a functional biopolymer for dysphagia-oriented nutrition. Practically, this approach provides a safer alternative to starch-based thickeners while promoting sustainable resource utilization, thereby addressing both clinical nutrition challenges and environmental concerns.