Application of ohmic and vacuum-assisted ohmic heating technologies for proofing composite millet-based doughs: Assessment of techno-functional properties, rheological behavior, and modeling of proofing kinetics

Abstract

This study presents a comprehensive investigation into the techno-functional properties, rheological behaviors, and the application of ohmic heating (OH) and vacuum-assisted ohmic heating (VAOH) as novel proofing techniques for composite millet-based bread doughs. Composite millet flours (CMF) were obtained by substituting refined wheat flour (RWF) with 20, 40, and 60% (w/w) mixed millet flour (finger and kodo millet flours in 1:1 ratio). Techno-functional and color attributes of flours were analyzed along with rheological characterization of the respective doughs. Furthermore, conventional proofing (35 °C), OH proofing (10, 15, 20, 25, and variable V), and VAOH proofing (20, 40, and 60 kPa) were performed. Expansion ratio (ER) obtained during proofing was fitted to the Gompertz model, demonstrating high accuracy (R²: 0.96–0.99). An increment in storage and loss modulus was observed with increasing millet content in the doughs. Stress relaxation test unveiled that doughs with higher millet substitution presented a greater resistance to deformation. Conventional proofing resulted in lower ER particularly for CMF doughs. OH proofing significantly (p < 0.05) reduced the time lag (t_lag) and improved expansion with increasing voltage. However, maintaining temperature homogeneity near 35 °C at higher voltages was challenging, so a voltage-time combination (variable V) was devised. For further improvement, VAOH proofing was performed that resulted in a 42.80% and 45.33% reduction in t_lag at 40 kPa (with variable V) for 40% and 60% CMF doughs, respectively, compared to OH proofing at variable V. This technological approach demonstrated scalable potential for improving proofing dynamics in composite millet-based dough systems.