Atmospheric Cold Plasma Treatment of Hard Wheat Flour and Soft Wheat Flour: Effects on Thiol Group Oxidation and Dough Rheology

Abstract Wheat flour quality depends largely on gluten protein cross-linking, which determines dough rheology, processing performance, and end product characteristics. Chemical oxidants are commonly used to modify gluten structure during wheat flour processing, but their use raises health and regulatory concerns. This study evaluated atmospheric cold plasma (ACP) as a novel, non-thermal treatment alternative for modifying hard wheat flour (HWF) and soft wheat flour (SWF). Flours were treated using a dielectric barrier discharge (DBD) ACP system at 50, 60, and 70 kV for 5, 6, and 7 min each with oxygen-rich modified air. The oxidative strength of ACP treatments was measured through methylene blue color discoloration with > 96% reduction, while protein oxidation in wheat flour was assessed by quantifying free thiol (-SH) groups. ACP treatment significantly reduced -SH content from 17.5 to 9.8 nmol mg −1 protein in HWF and from 13.9 to 9.5 nmol mg −1 protein in SWF at 70 kV, 7 min, indicating disulfide bond formation. Rheological analysis through frequency sweep and creep-recovery tests fitted to the Burgers model showed a strong correlation between thiol oxidation and viscoelastic enhancement. At 70 kV, 7 min of treatment, HWF dough exhibited a storage modulus (G′) of 57.8 kPa, which was significantly higher than control. While SWF showed comparable improvement of G′ of 39.3 kPa. Similarly, in creep and recovery behavior, ACP treatment significantly reduced compliance values. In HWF, ACP treatment reduced maximum creep compliance from 247.13 × 10 −3 Pa −1 to 63.45 × 10 −3 Pa −1 , confirming greater resistance to deformation and a stronger gluten network. These findings demonstrate that ACP-induced protein oxidation enhanced dough behavior without excessive cross-linking, demonstrating its potential as a clean-label alternative to chemical oxidants for wheat flour processing.