Umran Uygun

Dissipation of organophosphorus pesticides in wheat during pasta processing

For investigating the carryover of some organophosphorus pesticide residues in the cereal food chain from grain to consumer, a study was set up on durum wheat, semolina and pasta. Pesticide-free durum wheat was placed into a small-scale model of a commercial storage vessel and treated with pesticides (malathion, fenitrothion, chlorpyrifos methyl, and pirimiphos methyl) according to the raw material legislation of Turkey. The residue levels of insecticides were determined in wheat, semolina, and spaghetti produced from stored wheat at various time intervals during five months of storage. A multiresidue analysis was performed using GC equipped with an NPD. The confirmation was performed by GC-MS. The residue levels of insecticides in wheat exceeded the maximum residue limits (MRLs) for wheat. The storage period was generally not effective enough to reduce the residues in wheat to levels below the MRLs. Although a considerable amount of the insecticides remained in the semolina, spaghetti processing significantly reduced residue concentrations in general. Pirimiphos methyl was the most persistent of the insecticides and comparatively less substantial loss occurred during milling and spaghetti processing due to its physicochemical properties.

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.

Degradation of chlorfenvinphos in carrots during storage

In order to investigate the degradation products of chlorfenvinphos, organically grown carrots were treated with the pesticide. After storage at 5 °C for 3 months, the following compounds were detected by gas chromatography-mass spectrometric (GC-MS) analysis: 1-(2′,4′-dichlorophenyl)ethan-1-ol, 2,4-dichlorobenzoic acid, and 2,2-dichloro-1-(2′,4′-dichlorophenyl) vinyl alcohol. The metabolic fate of the pesticide was also investigated by use of 14C-ring-labelled chlorfenvinphos which was prepared using o-[14C]dichlorobenzene as a starting material. After a month of storage at room temperature, the following compounds were determined in carrots and in sand in which the carrots were buried after treatment with [14C]chlorfenvinphos: 2,2′,4′-trichloroacetophenone, 2,4-dichloroacetophenone and 2-chloro-1-(2′,4′-dichlorophenyl)vinyl alcohol. Separation of radioactive compounds was performed using high-performance liquid chromatography and a radioactivity flow detector. The identification of compounds was carried out by GC-MS.

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.

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).