Factors influencing bactericidal efficacy using atmospheric cold plasma (ACP) against Escherichia coli in wheat flour

This study aimed to evaluate operating factors that influence the bactericidal efficacy of atmospheric cold plasma (ACP) using wheat flour contaminated with Escherichia coli. It also investigated how non-optimized operating factors of ACP could affect wheat flour properties. Five operating factors (container volume, flour weight, shaking RPM, treatment time, and gas flow rate) were evaluated for the bactericidal effect of ACP using the Box-Behnken design. In addition, thermal and pasting properties were measured to assess the effect of non-optimized ACP operating conditions on wheat flour quality. ACP operating factors (volume of the container, shaking RPM, and treatment time) had significant effects on reducing E. coli in wheat flour (p < 0.05). The bactericidal effect also depended on the distance and contact area between the plasma jet and sample. The temperature at the flour surface increased (max. 70 ℃) when ACP treatment didn't provide sufficient space and optimized duration. Thermal, pasting, and gelling properties of ACP treated-wheat flour in a 10 mL container increased significantly compared to untreated wheat flour. Large amounts of samples, long processing time, and insufficient space contributed to overheating which leads to denaturation or change of the wheat flour properties. The present study proposed important data for industrial sterilization of wheat flour using ACP.