Optimization of Functional Gluten‐Free Cake Formulation Using Rice Flour, Coconut Flour, and Xanthan Gum via D‐Optimal Mixture Design

ABSTRACT

Prolamins in wheat, barley, and rye cause celiac disease (CD), non‐celiac gluten sensitivity (NCGS), and wheat allergies (WA). Although rice can be a suitable alternative, gluten‐free rice flour products are less technologically advanced. However, coconut flour and xanthan gum could enhance product quality, fiber content, and functional properties. This study employed a response surface D‐optimal mixture design to investigate the impact of substituting Sadri Hashemi rice flour (RF) (15.60%–31.19%) with low‐fat desiccated coconut flour (CF) (0%–15.59%) and xanthan gum (XG) (0%–0.31%) in 17 runs based on batter weight. Eleven responses were analyzed and exhibited significant and valid models (p < 0.0001), with satisfactory coefficient of determination (R² > 0.85) values and non‐significant lack of fit (p > 0.1). Substitution at all levels significantly increased batter viscosity (R² = 0.990) and specific weight (R² = 0.995). Differences in cake crumb color (ΔE) decreased when RF was substituted with CF, while maximum ΔE elevation was observed with 0.31% XG due to synergistic effects with 5.09% CF (R² = 0.974). Increasing the RF/XG ratio (0% CF) resulted in decreased water activity (a_w), while increasing CF increased a_w synergistically (R² = 0.986). Moisture and texture hardness increased significantly with RF substitution up to 7.518% CF and 0.170% XG and 8.944% CF and 0.285% XG, respectively (R² = 0.976 and 0.993). The volume index decreased with CF and XG (R² = 0.989). Sensory acceptances were reduced by increasing XG while improved with optimal CF levels, predicted at 6.415% (R² = 0.997), 6.784% (R² = 0.999), 9.001% (R² = 0.999), and 5.924% (R² = 0.999) for color, taste, texture, and overall acceptance, respectively. Two‐sided prediction interval confirmation runs with 95% confidence (p ≤ 0.05) validated the models' accuracy and prediction of optimized combinations. The optimized gluten‐free cake formula (23.395% RF, 7.795% CF, 0% XG) achieved an 88.0% desirability score. Developing valid regression models facilitates a comprehensive investigation of cake quality and sensory properties, ensuring a viable gluten‐free product for individuals with gluten‐related disorders.