Multivariate Chemometric and <scp>FTIR</scp> Insights Into the Effects of Rice Bran Extracts on Brown Rice Protein Bars

Protein bars are widely consumed functional snacks, yet their stability and sensory quality can deteriorate during storage. This study examined the impact of incorporating aqueous and ethanolic rice bran extracts-rich sources of phenolic compounds with antioxidant and antimicrobial properties-into brown-rice-based protein bars and evaluated their quality, molecular characteristics, and functional performance. Ethanolic extract, which contained 1.85-fold higher total phenolics than the aqueous extract, produced the most pronounced improvements. Bars fortified with 1% ethanolic extract showed a 37.27% increase in DPPH radical scavenging activity and a 25.74% increase in ferric reducing antioxidant power reducing power compared to the control, alongside a 46.6% reduction in peroxide value, demonstrating enhanced oxidative stability. These molecular effects translated into favorable textural changes, including a 53.63% reduction in hardness and a 28.35% decrease in gumminess, accompanied by an 8.55% improvement in overall sensory acceptability. FTIR spectroscopy demonstrated meaningful alterations in secondary structures, including reduced α-helix content and increased β-turn and random coil proportions in ethanolic treatments, indicating partial protein unfolding. These molecular changes corresponded strongly with texture and sensory improvements, as confirmed by multivariate analyses (Principal Component Analysis and Partial Least Squares Regression). Collectively, the results highlight that ethanolic rice bran extract more effectively enhances antioxidant performance, structural properties, and consumer acceptability than aqueous extract. The findings not only underscore its potential as a natural preservative and functional ingredient in high-protein snacks but also support the valorization of rice bran as a sustainable source of nutraceutical compounds.