Impact of dough mixing pressure with Air and CO2 gases on dough and bread properties

• Bread dough mixing was carried in a pressure mixer with air and CO 2 as headspace gases. • The applied pressure was either atmospheric pressure or 0.5 bar gauge pressure. • A model was proposed to predict dough void fraction at end of fermentation. • CO 2 mixing yielded in less uniform crumb structure with disproportionation. • Air mixing yielded in bigger volume and a more uniform crumb structure. This study investigated the effect of controlling headspace pressure and gas atmosphere during dough mixing on dough aeration and bread quality. Using a specialized mixer, doughs were mixed with either air or CO 2 under atmospheric pressure and 0.5 bar gauge pressure. Dough aeration (void fraction) was monitored at key breadmaking stages; end of mixing, after sheeting and after fermentation with a target final void fraction of 0.75 for optimal bread volume. A predictive model estimated the expansion ratio needed to achieve this target void fraction. Although the target was not fully reached post-fermentation, doughs mixed with air at 0.5 bar gauge pressure demonstrated a higher ε F = 0.64 and SV of 4.54 cm 3 /g compared to those mixed with CO 2 at the same elevated pressure (ε F = 0.60 & SV = 3.55 cm 3 /g). Lower SV and larger, irregular gas bubbles in CO 2 doughs were attributed to gas bubble disproportionation and loss during sheeting, as well as the weakening of the gluten network due to oxygen depletion. The calculated N required to reach the target void fraction was slightly lower for air (3.20 ± 0.06) than for CO 2 (3.36 ± 0.06), suggesting more efficient gas retention and dough expansion under air-enriched conditions. These finding suggest that while CO 2 may stabilize gas bubbles during mixing, oxygen from air is essential for a strong gluten network and uniform breadcrumb structure. Controlling the mixing atmosphere and pressure, offer a promising approach for optimizing dough aeration and bread quality