Transformation of ochratoxin A during bread-making processes

Ochratoxin A (OTA) – secondary metabolite of fungi from genera Aspergillus and Penicillium may mainly contaminate cereal-based food. Thermal processing (including baking) may reduce the levels of OTA, but may also produce racemic mixtures with the 2′R-ochratoxin A (2′R-OTA) isomer. In this study, the stability of OTA during rye bread production processes and pizza wheat base production processes (including dough kneading, dough fermentation, and baking) was investigated. The bread was prepared using a rye flour naturally contaminated with OTA (concentration 6.41±0.52 μg/kg) and yeast. The bread was baked for 40 min at 180°C, or for 70 min at 240°C. The pizza bases were prepared by using wheat flour artificially contaminated with OTA (concentration 8.0 or 18.0 μg/kg). The bases were baked for 8 min at 320°C or for 6 min at 370°C. No statistically significant changes in OTA concentration were found after the dough kneading and fermentation production process stages. OTA concentrations in the crumb of the baked breads and pizza bases were also similar to the concentrations in the fermented dough. However, OTA concentrations in the crust decreased as compared to the fermented dough by 25.6% for the bread baked at 180°C, 23% for the bread baked at 240°C, and 8.0%–25.4% for the pizza bases, depending on the OTA concentration in the dough and the baking temperature (lower concentrations were associated with higher temperatures). Partial degradation of OTA in the crust of the baked products was accompanied by slight OTA racemisation. Approximately 3.5% of the OTA in the crust of the rye bread baked at 240°C was transformed into 2′R-OTA, increasing its level to 0.18 μg/kg. Briefly, 2.2%–10.1% of the OTA in the crust of the pizza bases was transformed into 2′R-OTA, increasing its levels to 0.13–1.57 μg/kg, depending on the baking temperature (higher concentrations were associated with higher temperature). It is worth noting that so far, apart from a few studies on transformation of OTA during roasting of coffee beans, these mechanisms during baking of cereal-based products are practically unknown