Impact of cold plasma on microbial load and quality properties of maize flour

The control of microbial contamination in flour represents a significant challenge for food safety. Traditional thermal methods often compromise product safety and quality as they cause undesirable changes. In addition, many existing technologies suffer from limitations such as uneven treatment, safety issues, and mainly superficial effects. To overcome these problems, a prototype system integrating atmospheric dielectric barrier discharges (DBD) cold plasma with mechanical fluidization was developed and applied to naturally contaminated maize flour for 5, 10, 20 and 30 min. Bacterial and fungal inactivation, physico-chemical properties, particle size distribution and microstructural properties were evaluated. A gradual reduction in mesophilic aerobic bacteria (MAB) was observed, with complete inactivation achieved after 30 min; however, bacterial regrowth was detected after 16 days of storage. Filamentous fungi were completely inactivated after 10 min and although partial recovery occurred during storage, fungal loads remained below those of the control. Fungal diversity was also altered, with Aspergillus flavus being more sensitive than Aspergillus oryzae. A notable reduction in water content and activity was observed for longer treatments. Modification of particle size and morphology likely occurred in the process with plasma associated to mechanical fluidization of flour. Overall, the effectiveness of ACP was influenced by treatment duration and fungal species, highlighting both its potential and limitations in flour decontamination, without detrimental effects on the selected physical quality attributes of the product.