Modelling thermal degradation of zearalenone in maize bread during baking.

The thermal degradation of zearalenone (ZEA) was investigated using a crust-like model, representing maize bread, which was prepared with naturally contaminated maize flour. Model samples were heated under isothermal conditions at the temperature range of 100-250°C. No reduction was observed at 100°C. Thermal degradation rate constants (k) were calculated as 0.0017, 0.0143 and 0.0216 min(-1) for 150, 200 and 250°C, respectively. Maize bread baked at 250°C for 70 min was used to test the capability of model kinetic data for the prediction of ZEA reduction. The time-temperature history in the crust and crumb parts was recorded separately. Partial degradation of ZEA at each time interval was calculated by means of the corresponding k-values obtained by using the Arrhenius equation, and the total reduction occurring at the end of the entire baking process was predicted. The reduction in the crumb and crust of bread was also experimentally determined and found to be consistent with the predicted values. It was concluded that the kinetic constants determined by means of the crust-like model could be used to predict the ZEA reduction occurring during baking of maize bread.

Thermal degradation of deoxynivalenol during maize bread baking.

The thermal degradation of deoxynivalenol (DON) was determined at isothermal baking conditions within the temperature range of 100-250°C, using a crust-like model, which was prepared with naturally contaminated maize flour. No degradation was observed at 100°C. For the temperatures of 150, 200 and 250°C, thermal degradation rate constants (k) were calculated and temperature dependence of DON degradation was observed by using Arrhenius equation. The degradation of DON obeyed Arrhenius law with a regression coefficient of 0.95. A classical bread baking operation was also performed at 250°C for 70 min and the rate of DON degradation in the bread was estimated by using the kinetic data derived from the model study. The crust and crumb temperatures recorded during bread baking were used to calculate the thermal degradation rate constants (k) and partial DON degradations at certain time intervals. Using these data, total degradation at the end of the entire baking process was predicted for both crust and crumb. This DON degradation was consistent with the experimental degradation data, confirming the accuracy of kinetic constants determined by means of the crust-like model.

Multiple-stage extraction strategy for the determination of deoxynivalenol in maize.

The effects of single- and multiple-stage extraction procedures on the extraction yield of deoxynivalenol (DON) from maize were studied. Naturally contaminated maize samples with different DON levels were used for analyses. In the multiple-stage procedure, extraction of the ground samples was sequentially performed up to five times with water as the extraction solvent. The extraction yield of DON was determined for each stage. When the results obtained by single-stage extraction were compared with the results from multiple-stage extraction, there was a considerable difference between the extraction yields. The results showed that a single-stage procedure underestimated the concentration in maize by a factor of up to 24% depending on the initial DON level. The extractability was an exponential function, which could be used to optimize the multiple extraction conditions during the analysis of maize for DON. In general, two extraction steps were acceptable for the extraction of approximately 90% of DON from maize. In the study, the effect of extraction time on the extractability was also investigated. The samples were extracted for different times at room temperature by single-stage extraction procedure. Although, 15-min extraction was more effective than the shorter or longer extraction procedures, the differences were not statistically significant (p > 0.05).