Oxidation-dependent functionality of l-ascorbic acid in vacuum-mixed dough: Linking gluten redox regulation, water...

l-Ascorbic acid (L-AA) is an oxidation-dependent dough improver, but its functionality under oxygen-limited vacuum mixing remains unclear. This study separately evaluated the effects of L-AA level, vacuum degree, mixing time, and resting time on L-AA oxidation, gluten redox status, water distribution, dough mechanical properties, and cooked dough sheet texture. Although the calculated headspace oxygen content exceeded the stoichiometric requirement for complete oxidation, L-AA remained incompletely oxidized, consistent with limited transfer of oxygen from the gas phase into the aqueous phase of the dough. Nevertheless, L-AA effectively promoted gluten redox regulation by reduced free sulfhydryl groups and increased disulfide bonds, confirming that it remained functional under vacuum. Moderate vacuum mixing, particularly at 0.06 MPa vacuum degree, enhanced water immobilization and dough strength. When vacuum degree increased from 0 to 0.06 MPa, T₂₁ decreased from 2.79 to 2.13 ms and from 2.52 to 2.07 ms in the 120 and 250 mg/kg L-AA groups, respectively, while toughness and extensibility increased from 4.22 N and 40.65 mm to 4.59 N and 48.83 mm in the 120 mg/kg L-AA group. Dough mechanical properties and cooked texture generally reached their optimal values after 240 s of medium-speed mixing, whereas further mixing caused deterioration. Structural equation modeling identified L-AA level as the strongest predictor of gluten redox status. Gluten redox status was positively associated with dough strength, which was the principal predictor of cooked dough sheet texture. These findings distinguish the roles of oxygen limitation, mechanical input, and post-mixing equilibration in the functionality of L-AA under vacuum mixing, providing a mechanistic basis for precise dough quality regulation.