Deoxynivalenol (DON) and fumonisins B-type (FBs), mycotoxins synthesized by Fusarium spp., cause serious health problems after their intake. These compounds are frequently found in maize and wheat, the most consumed cereals worldwide and main hosts of Fusarium, making them a food safety problem. This work studies the effect of the maize/wheat-based breadmaking process on the concentrations of DON and FBs. Breads were made using contaminated maize flour (40 %) mixed with uncontaminated wheat flour (60 %). Three factors were analyzed: mycotoxin contamination level (DON: 1.20 or 0.8 mg/kg; FBs: 1.28 or 0.61 mg/kg), sourdough use (absence, artisan or commercial) and fermentation time (2 or 12 h). Doughs were baked at 200 °C for 40 min. DON and FBs were determined by HPLC-DAD and HPLC-FLD, respectively. Additionally, sourdough microbiota was identified. The only isolated yeast was Saccharomyces cerevisiae, while lactic acid bacteria showed great variability, being Lactobacillus plantarum the most common. FBs concentration remained stable during fermentation; while for DON, the highest change was observed in the loaves with an initial concentration of 1.20 mg/kg, commercial sourdough use and 12 h fermented, showing a 28 % increase in its concentration. After baking, mycotoxin reduction was observed under all conditions, except in the aforementioned one that still showed a 16 % of DON increase. Results indicate that the reduction of DON during breadmaking may not be enough to ensure food safety from borderline contaminated flour to meet legal limits. However, bread with FBs levels below the maximum limits can be produced, even when using contaminated flour. | This work was supported by the Spanish Ministry of Science and Innovation (project PID2020-114836RB-I00, funded by MCIN/AEI541/ 10.13039/501100011033). Alexandre Vicens-Sans acknowledges the EU through Project 101079173-FunShield4Med (HORIZON-WIDERA- 2021-ACCESS-03).