The Effect of Hydration Levels on the Rheological and Thermomechanical Properties of Different Gluten-Free Flours

The growing demand for gluten-free products has increased the need for a better understanding of the rheological behavior of alternative flours and their suitability for bakery applications. This study aimed to evaluate the effect of different hydration levels on the rheological properties of gluten-free flours and compare their behavior with that of wheat flour. Rice flour, corn flour, chickpea flour, buckwheat flour, and wheat flour were analyzed using Mixolab 2 at hydration levels of 55%, 58%, and 60%. The resulting torque curves were examined to assess dough development, stability, and behavior during mixing and heating. Differences among flour types were observed throughout dough development and protein weakening. One-way ANOVA identified significant flour-type effects for all 19 Mixolab variables at 55% and 60% hydration and for 17 of 19 variables at 58%, where T(C4) and γ-slope were not significant. Across the three common hydration levels, two-way ANOVA showed significant main effects of flour type and hydration for every variable and significant flour × hydration interactions for all variables (p ≤ 0.035), confirming flour-specific hydration responses. Among the gluten-free flours, buckwheat maintained the most stable and comparatively robust torque profile, rice was particularly sensitive at 60% hydration, and corn and chickpea showed pronounced structural weakening during heating, most notably chickpea. A focused principal component analysis (PCA) of the five directly measured torque points (C1–C5), using the hydration levels common to all flour types, identified a dominant first component that explained 76.9% of the total variance. The first two axes together accounted for 94.3% and provided a concise two-dimensional representation of flour-specific and hydration-dependent differences. These findings highlight the importance of hydration management in gluten-free formulations and provide useful information for optimizing bakery processes involving alternative flours.