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).

An application of linear regression technique for predicting bulgur yield and quality of wheat cultivars.

Grains of 26 Turkish wheat cultivars and advanced breeding lines were used in this study. Simple correlations between a number of quality parameters to predict bulgur yield and bulgur cooking quality were determined. Highly significant correlations between bulgur yield and each of the thousand-kernel weight and the sum of the grain over 2.8 + 2.5 mm sieves were obtained for both durum and bread wheat samples (p < 0.01). The regression equations showed that the models involving two variables (the thousand-kernel weight and the thickness of the grain for durum wheat samples; the thousand-kernel weight and the length of the grain for bread wheat samples) resulted in the highest R2 values. For an assessment of the influence of all factors on bulgur cooking properties (total organic matter: TOM and colorimetric test values), simple and multiple regression analyses were used to find equations that predict best the relationship between various quality parameters and bulgur cooking properties. The models involving two variables; the vitreousness and the dry gluten contents for the durum wheat samples and SDS sedimentation test value and wheat protein content for the bread wheat samples resulted in the highest R2 for the TOM value.

Commercial milling of suni bug (Eurygaster spp.) damaged wheat.

In some wheat growing countries, considerable quantities of commercial wheat are rendered unusable in standard milling because of pre-harvest damage of the grain by protease-injecting insects. The possibility of mitigating the detrimental effects of bug damage by eliminating the mill streams of lower quality from straight run flour was investigated. The changes in the amount of damaged kernels by cleaning and washing prior to milling were also examined. Dry cleaning decreased the level of insect damage from 26.4% to 23.0%. A further improvement to 12.8% was obtained by removing the light-density bug-damaged kernels by washing. There were substantial differences among the mill streams of the commercial mill as evaluated by the standard and modified sedimentation tests and standard alveograph test. The best streams were those from the first, second, third and fourth reductions.

Effects of wheat maturation stage and cooking method on dietary fiber and phytic acid contents of firik, a wheat-based local food.

Samples of two durum wheat cultivars (cvs. Duraking and Ege 88) at different maturation stages (13, 16, 19, 22, 25 days post anthesis) were processed into firik (a wheat-based specialty food) using two different cooking methods: roasting (scorching) on flames and boiling at atmospheric pressure. Both the acid detergent and neutral detergent fiber contents of the firiks produced from two durum wheat samples decreased significantly (p < 0.01) with maturation. Total P contents of the firiks of both cultivars produced by both methods showed a significant downward trend within the period of maturation while their phytic acid contents showed a significant upward trend (p < 0.01). It was possible to obtain a reduced phytic acid, high fiber product from the wheats harvested at early stages of maturation (13 and 16 days after anthesis).

The effect of zinc-supplemented bread consumption on school children with asymptomatic zinc deficiency.

BACKGROUND: Zinc deficiency has been seen in developing countries in which grain-based vegetable protein is consumed more often than animal protein. This study was done to emphasize the importance of zinc-fortified foods and to investigate bioavailability of zinc in zinc-fortified bread. METHODS: Serum zinc concentrations in healthy 7- to 11-year-old school children were determined. In 24 of 101 children serum zinc concentrations were below 65 micrograms/ul. These 24 children with asymptomatic zinc deficiency were divided into two equal groups. The 12 children with low serum zinc concentrations received the zinc-fortified bread providing 2 mg/kg/day elemental zinc acetate for 90 days (zinc-supplemented group), whereas the other 12 children received the same quality bread with no zinc fortification (control group). RESULTS: By the end of the period, the zinc-supplemented group had significantly higher serum and leukocyte zinc concentrations (p < 0.01) and the weight, serum albumin levels, and alkaline phosphatase increased (p < 0.01). Immune functions improved, evidenced by conversion of delayed hypersensitivity skin reactions. Zinc-fortified bread (2 mg/kg/day) caused no side effects or manifestations of zinc toxicity. CONCLUSIONS: The results indicate that the bioavailability of zinc in the bread is satisfactory. The use of zinc-fortified bread was found to be an economical and readily accessible method to eliminate zinc deficiency and to prevent further occurrence.