Single First-order Kinetics Model Research Articles

The particle sizes of milled wheat fractions affect the in vitro starch digestibility and quality parameters of wire-cut cookies made thereof.

Slow digestion of starch is linked to various health benefits. The impact of wheat particle size on in vitro starch digestibility and quality of wire-cut cookies was here evaluated by including four soft wheat fractions [i.e. flour (average diameter, 83 μm), fine farina (643 μm), coarse farina (999 μm) and bran (1036 μm)] in the recipe. The susceptibility of starch in these fractions to in vitro digestion decreased with increasing particle size, resulting in a 76% lower digestion rate for coarse farina than for flour as found with the single first-order kinetic model. Starch was protected from hydrolysis likely due to delayed diffusion of pancreatic α-amylase through the intact farina cell walls. When 20-65% starch in flour for the control cookie recipe was substituted with the same percentages in fine and coarse farina, the starch digestion rate decreased when substitution levels increased. A 62% lower digestion rate was found at 65% substitution with coarse farina. Cell wall intactness was largely preserved in the cookies and most of the starch appeared as ungelatinised granules. Further, the cookie spread ratio during baking was 48% and 33% higher and the cookies were 63% and 57% less hard than control cookies when made with 65% fine farina and 65% coarse farina, respectively. The relatively low specific surface area of large wheat particles resulted in low water absorption and less dense packing. In conclusion, encapsulation of starch by intact cell walls in coarse wheat fractions makes them promising ingredients when developing starchy food products for controlled energy release.

Combined techniques for revealing the mechanism beneath the inhibition effects of pectin on gluten digestibility using static in vitro gastro-duodenal protocols

In the current study, how pectin retards the digestibility of wheat gluten was investigated using a static in vitro gastric-duodenal model. The degree of protein hydrolysis was estimated using the o-phthaldialdehyde method, while the in vitro digestograms were mathematically fitted using a single first-order kinetics model. Peptides' profile, free amino acids compositions, gluten-pectin interactions and their effects on enzymatic activities of proteolytic enzymes as well as on the gluten secondary structures under digestive conditions were studied using combined techniques. Results showed that pectin could retard gluten digestibility through 1). preferential absorption to insoluble gluten aggregates by electrostatic interactions; 2). increasing the helix and reducing the β-sheet content of the solubilized gluten protein fractions in terms of their secondary molecular structures; 3). reducing pepsin activity by forming negatively charged pectin-gluten mixtures which then interacted with the positively charged pepsin molecules. The deeper insight into gluten-pectin interactions and their influences on gluten digestibility under gastrointestinal conditions provides important clues for developing effective forms of dietary fiber to improve the nutritional benefits of plant protein in individuals.

The particle sizes of milled wheat fractions affect the in vitro starch digestibility and quality parameters of wire-cut cookies made thereof.

Slow digestion of starch is linked to various health benefits. The impact of wheat particle size on in vitro starch digestibility and quality of wire-cut cookies was here evaluated by including four soft wheat fractions [i.e. flour (average diameter, 83 μm), fine farina (643 μm), coarse farina (999 μm) and bran (1036 μm)] in the recipe. The susceptibility of starch in these fractions to in vitro digestion decreased with increasing particle size, resulting in a 76% lower digestion rate for coarse farina than for flour as found with the single first-order kinetic model. Starch was protected from hydrolysis likely due to delayed diffusion of pancreatic α-amylase through the intact farina cell walls. When 20-65% starch in flour for the control cookie recipe was substituted with the same percentages in fine and coarse farina, the starch digestion rate decreased when substitution levels increased. A 62% lower digestion rate was found at 65% substitution with coarse farina. Cell wall intactness was largely preserved in the cookies and most of the starch appeared as ungelatinised granules. Further, the cookie spread ratio during baking was 48% and 33% higher and the cookies were 63% and 57% less hard than control cookies when made with 65% fine farina and 65% coarse farina, respectively. The relatively low specific surface area of large wheat particles resulted in low water absorption and less dense packing. In conclusion, encapsulation of starch by intact cell walls in coarse wheat fractions makes them promising ingredients when developing starchy food products for controlled energy release.

Dissipation kinetics of tebuconazole on Malus domestica (Golden Delicious and Jonathan) in an apple orchard from north-eastern Romania

Tebuconazole (TEB) dissipation behavior on Golden Delicious and Jonathan leaf, bark, peel and flesh apple samples was investigated in the present work. The interest fungicides were sequentially applied as a spray in four foliar applications, in full agreement with an apple orchard-protection program recommended by Bayer. For studying TEB dissipation, apple tree related samples were collected in advance (reference) and as soon as applications dried out (3 h), and then at 2, 5, 7.5, 10, and 15 day after the treatment. Reference apple tree samples were analyzed by gas chromatography tandem mass spectrometry for their corresponding chemical and phytochemical composition. Tebuconazole dissipation on apple leaf, bark and peel could be adequately described by a single first-order kinetic model. In apple flesh samples traces of TEB were not detected. Higher TEB dissipation rate constant was observed in apple leaf than in peel and bark apple samples. The half-life time of TEB varies in the 2.71–16.03 d range and might reach a critical value of 1 d under the most reactive circumstances. The results obtained in the present study show that the dissipation parameters are sensitive to the composition of used combined fungicide formulations and also to their corresponding applied dose.

Isolation, screening, and crude oil degradation characteristics of hydrocarbons-degrading bacteria for treatment of oily wastewater.

The aim of this study was to isolate hydrocarbons-degrading bacteria for treatment of oily wastewater from long-standing petroleum-polluted sediments in Bohai Bay, China. Six hydrocarbons-degrading bacteria were screened and identified as Pseudomonas sp. and Bacillus sp. A new approach using a combination of various bacterial species in petroleum biodegradation was proposed and evaluated for its degradation characteristics. Gas chromatography-flame ionization detection (GC-FID) analysis showed that mixed bacterial agents (YJ01) degraded 80.64% of crude oil and 76.30% of crude oil alkanes, exhibiting good biodegradation effect. Besides, after 14 days of culture, the biodegradation assessment markers, pristane and phytane, showed significant degradation rates of 46.75% and 78.23%, respectively. Kinetic analysis indicated that the degradation trends followed a single first-order kinetics model and the degradation half-life (t1/2) of 15 g/L crude oil was significantly shorter (5.48 days). These results indicated that YJ01 could degrade a wider range of hydrocarbons as well as some recalcitrant hydrocarbon components, and can be applied for bioremediation and treatment of oil-contaminated environment.

Comparison Of Empirical Models For Estimating The Mineralization Potential Of Soil Nitrogen

Modeling is an attempt to describe a natural event mathematically. The modeling of N mineralization process has a dual interest, agronomical and ecological. The objective of this study is to evaluate several mathematical models to describe the nitrogen mineralization process of soil samples. These samples were collected from 34 sites spatially distributed in the semi-arid region of El-Madher (the Aures area, north-east of Algeria). Using an auger, the systematic surveys have been carried out and composite samples of soils were collected in the field, and subjected to physical and chemical analyzes. In order to track the kinetic organic nitrogen mineralization, similar samples were collected and taken into cool boxes have been incubated in laboratory, sieved (2 mm) and stored at 4°C before use and then incubated at 28°C for 56 weeks. To facilate comparison, all results have been statistically analyzed, by nonlinear regression and analysis of variance method. Four empirical models were tested to fitt the value found experimentally. The linear kinetics model Nm=k t Ni, the single first-order kinetics model (MI) Nm = Ni e-kt + No (1 - e-kt), the double first-order and the exponential kinetics model (MII) Nm=Ni e-kt + No (1 - e-kt) + e-ht and the hyperbolic kinetics model (MH) Nm=NoH.t/(Tc+t) Ni were used to simulate the cumulative mineralized N (NH4+-N and NO3- -N) in the laboratory incubation. In order to test the performance and robustness of the different models three goodness of fit (coefficient of determination R2, Root Mean Square RMS and Mean Relative Error RMSE) were used. Moreover, the parameters obtained by the different models determined the predictions of nitrogen mineralization. The best results were obtained using the double first-order and exponential kinetics model. The results showed no significant difference between nitrogen mineralized for 56 weeks and nitrogen predicted by various models. However, the N predicted by the MII appears to be the best compared to other models. Indeed, the overestimation of nitrogen potentially mineralizable (N0) obtained by this model was relatively lower than other models. This has been confirmed by the study of multiple correlations between net mineral nitrogen and nitrogen predicted by each model. Thus, the results obtained showed a strong positive correlation between mineralized nitrogen values and those of nitrogen predicted by the different models. The correlation coefficients values indicate the folowing order MII (r = 0.878)> MI (r = 0.748)> MH (r = 0.709). The MII model has, therefore, highlighted that two pools of organic matter that mineralize simultaneously were detected in soil. One pool is stable and the other one is labile. One pool evolves with first-order kinetics and the other with exponential kinetics.

Influence of Herbicide Triasulfuron on Soil Microbial Community in an Unamended Soil and a Soil Amended with Organic Residues.

The effect of organic amendments and pesticides on a soil microbial community has garnered considerable interest due to the involvement of microorganisms in numerous soil conservation and maintenance reactions. The aim of this work was to assess the influence on a soil microbial community of the simultaneous application of the herbicide triasulfuron at three doses (2, 10, and 50 mg kg-1), with an organic amendment [sewage sludge (SS) or green compost (GC)]. Dissipation kinetics, soil microbial biomass, dehydrogenase activity (DHA) and respiration, and the profile of phospholipid fatty acids (PLFAs) extracted from the soil, were determined in unamended (S) soil and amended (S+SS and S+GC) ones. Triasulfuron dissipation followed the single first-order kinetics model. Half-life (DT50) values were higher in the amended soils than in the unamended one for the 10 and 50 mg kg-1 doses. The dissipation rates were lower in the S+GC soil for the three herbicide doses applied. In general, soil biomass, DHA and respiration values increased in SS- and GC-amended soils compared to the unamended one. DHA values decreased (S and S+SS) or increased (S+GC) with the incubation time of soil with herbicide at the different doses applied. Respiration values increased with the herbicide doses applied and decreased with the incubation time, although maximum values were obtained for soils treated with the highest dose after 70 days of incubation. PLFA analysis indicated different effects of triasulfuron on the soil microbial community structure depending on the organic amendments. While the increasing triasulfuron doses resulted in deeper alterations in the S soil, the time after triasulfuron application was the most important variation in the S+SS and S+GC soils. The overall results indicate that the soil amendment has an effect on herbicide dissipation rate and the soil microbial community. Initially, a high dose of triasulfuron had detrimental effects on the soil microbial community, which is important in the case of the long-term use of this compound.

Evaluation and simulation of nitrogen mineralization of paddy soils in Mollisols area of Northeast China under waterlogged incubation.

BackgroundUnderstanding the nitrogen (N) mineralization process and applying appropriate model simulation are key factors in evaluating N mineralization. However, there are few studies of the N mineralization characteristics of paddy soils in Mollisols area of Northeast China.Materials and methodsThe soils were sampled from the counties of Qingan and Huachuan, which were located in Mollisols area of Northeast China. The sample soil was incubated under waterlogged at 30°C in a controlled temperature cabinet for 161 days (a 2: 1 water: soil ratio was maintained during incubation). Three models, i.e. the single first-order kinetics model, the double first-order kinetics model and the mixed first-order and zero-order kinetics model were used to simulate the cumulative mineralised N (NH4+-N and TSN) in the laboratory and waterlogged incubation.Principal resultsDuring 161 days of waterlogged incubation, the average cumulative total soluble N (TSN), ammonium N (NH4+-N), and soluble organic N (SON) was 122.2 mg kg-1, 85.9 mg kg-1, and 36.3 mg kg-1, respectively. Cumulative NH4+-N was significantly (P < 0.05) positively correlated with organic carbon (OC), total N (TN), pH, and exchangeable calcium (Ca), and cumulative TSN was significantly (P < 0.05) positively correlated with OC, TN, and exchangeable Ca, but was not significantly (P > 0.05) correlated with C/N ratio, cation exchange capacity (CEC), extractable iron (Fe), clay, and sand. When the cumulative NH4+-N and TSN were simulated, the single first-order kinetics model provided the least accurate simulation. The parameter of the double first-order kinetics model also did not represent the actual data well, but the mixed first-order and zero-order kinetics model provided the most accurate simulation, as demonstrated by the estimated standard error, F statistic values, parameter accuracy, and fitting effect.ConclusionsOverall, the results showed that SON was involved with N mineralization process, and the mixed first-order and zero-order kinetics model accurately simulates the N mineralization process of paddy soil in Mollisols area of Northeast China under waterlogged incubation.

Mathematical prediction of imidacloprid persistence in two Croatian soils with different texture, organic matter content and acidity under laboratory conditions

In the present laboratory study, persistence of imidacloprid (IMI) as a function of initial insecticide concentration and soil properties in two Croatian soils (Krk sandy clay and Istria clay soils) was studied and described mathematically. Upon fitting the obtained experimental data for the higher concentration level (5 mg/kg) to mathematical models, statistical parameters (R 2, scaled root mean squared error and χ 2 error) indicated that the single first-order kinetics model provided the best prediction of IMI degradation in the Krk sandy clay soil, while in the Istria clay soil biphasic degradation was observed. At the lower concentration level (0.5 mg/kg), the biphasic models Gustafson and Holden models as well as the first-order double exponential model fitted the best experimental data in both soils. The disappearance time (DT50) values estimated by the single first-order double exponential model (from 50 to 132 days) proved that IMI can be categorized as a moderately persistent pesticide. In the Krk sandy clay soil, resulting DT50 values tended to increase with an increase of initial IMI concentration, while in the Istria clay soil, IMI persistence did not depend on the concentration. Organic matter of both experimental soils provided an accelerating effect on the degradation rate. The logistic model demonstrated that the effect of microbial activity was not the most important parameter for the biodegradation of IMI in the Istria clay soil, where IMI degradation could be dominated by chemical processes, such as chemical hydrolysis. The results pointed that mathematical modeling could be considered as the most convenient tool for predicting IMI persistence and contributes to the establishment of adequate monitoring of IMI residues in contaminated soil. Furthermore, IMI usage should be strictly controlled, especially in soils with low organic matter content where the risk of soil and groundwater contamination is much higher due to its longer persistence and consequent leaching and/or moving from soil surface prior to its degradation.

Degradação do herbicida sulfentrazone em dois solos de Mato Grosso do Sul

Realizou-se este trabalho com o objetivo de avaliar a degradação do herbicida sulfentrazone em dois solos (Latossolo Vermelho Distroférrico típico e Neossolo Quartzarênico Órtico típico) utilizados na cultura da cana-de-açúcar, em Mato Grosso do Sul, e avaliar também a influência da temperatura, umidade e profundidade na taxa de degradação. Os experimentos de degradação foram realizados utilizando-se solos incubados em diferentes condições de umidade (50 e 80% da capacidade de campo - CC), temperatura (30 e 40 ºC) e profundidade (0-30 e 50-70 cm). Os resultados das concentrações remanescentes do sulfentrazone no solo foram, em função do tempo, ajustados aos modelos de cinética de primeira ordem (SFO) e ao de cinética de primeira ordem para multicompartimentos (FOMC). O sulfentrazone foi menos persistente em condições de maior umidade (80% da CC), temperatura mais elevada (40 ºC) e em horizontes superficiais do solo (0-30 cm). A degradação do sulfentrazone para a maioria das condições estudadas foi melhor descrita pelo modelo FOMC. Os valores de meia-vida para o sulfentrazone nas diferentes condições de umidade, temperatura e profundidades avaliadas, variaram de 34 a 116 dias.

Toxicokinetic variation in 15 freshwater arthropod species exposed to the insecticide chlorpyrifos

Recent advances in modeling the processes of the toxicity of chemicals-toxicokinetics (TK) and toxicodynamics (TD)-are improving environmental risk assessment (ERA) through prediction of effects from time-varying exposure. This has been achieved by linking chemical fate and toxicological effects mechanistically, based on internal concentrations, through the tissue residue approach. However, certain questions remain: for example, how do TK and TD differ among species and how does this relate to differences in species sensitivity? In a series of experiments, we studied the TK of [(14)C]chlorpyrifos in 15 freshwater arthropod species, two of which were studied in juvenile and adult life stages. Uptake (k(in)) and elimination (k(out)) rate constants were fitted using a one-compartment single first-order kinetic model. The application of two complementary parameter estimation methods facilitated the calculation of bioconcentration factors (BCF) with prediction intervals and 95% depuration times (t(95)) for all tested species. Extremely slow elimination was observed in some species as well as high overall variation in k(in), k(out), BCF, and t(95) across the tested aquatic arthropod species. This variation has implications for the development of TKTD approaches in ERA, including assessing fluctuating exposure concentrations and the interpretation of observed toxicity responses in the laboratory and in the field.

Thermal analysis of Moroccan phosphates 'Youssoufia' in an oxidative atmosphere by TG and DSC

A non-isothermal experimental study using thermogravimetry (TG) and differential scanning calorimetry (DSC) was conducted for investigation the oxidation reactivity of natural phosphate and its demineralised products. The analyses were carried out in oxygen atmosphere and at different heating rate (5, 10, 20, 30, 50, 60°C min-1) up to 1000°C. The results indicated that the material washed with HCl from the original phosphate, mainly apatite and carbonates of calcium and magnesium, as well as with HCl/HF, silicates minreals, had an inhibition effect during oxidation reactions of organic material. The increase of the heating rate shifted the reactions to higher temperatures. In addition, kinetic parameters were determined by assuming a single first-order kinetic model, using the Coats-Redfern method. The influences of demineralization process of natural phosphate and the heating rate were examined and discussed.

Thermoanalytical Study of O,O'-dibenzoyl-(2R, 3R)-Tartaric Acid SMC

A non-isothermal experimental study using thermogravimetry (TG) and differential scanning calorimetry (DSC) was conducted for investigation the oxidation reactivity of natural phosphate and its demineralised products. The analyses were carried out in oxygen atmosphere and at different heating rate (5, 10, 20, 30, 50, 60°C min-1) up to 1000°C. The results indicated that the material washed with HCl from the original phosphate, mainly apatite and carbonates of calcium and magnesium, as well as with HCl/HF, silicates minreals, had an inhibition effect during oxidation reactions of organic material. The increase of the heating rate shifted the reactions to higher temperatures. In addition, kinetic parameters were determined by assuming a single first-order kinetic model, using the Coats-Redfern method. The influences of demineralization process of natural phosphate and the heating rate were examined and discussed.

MODELING THERMAL SOFTENING KINETICS OF POTATOES USING FRACTIONAL CONVERSION OF RHEOLOGICAL PARAMETERS

Texture degradation in potatoes was investigated during heating of cylindrical test samples, 15 mm diameter and 30 mm long, in water at 60, 70, 80 and 90C by mechanical testing. The rheological parameters obtained from the axial and radial compression, creep and stress relaxation tests decreased exponentially with an increase in heating duration and temperature approaching steady levels corresponding to the remaining texture after prolonged heating. A single first‐order kinetic model described the changes in various rheological parameters due to thermal softening of potatoes using fractional conversion technique indicating very high values of the coefficient of determination (R2 &gt; 0.97). In general, the visco‐elastic test parameters were relatively more sensitive to texture degradation in potatoes in comparison with the quasi‐static test parameters. Overall comparison showed that elasticity and viscosity parameters in Kelvin component of the 4‐element model (E2 and η2) from creep tests and elasticity moduli from axial and radial compression tests (Ea and Er) best presented the texture degradation kinetics in potatoes with R2 ranging from 0.98 to 0.99.

Thermogravimetrically and differential scanning calorimetrically derived kinetics of oil shale pyrolysis

Thermogravimetry (TG) and differential scanning calorimetry (d.s.c.) were used to investigate the kinetics of non-isothermal pyrolysis of Aleksinac oil shale from Yugoslavia. The samples used included oil shale, demineralized oil shale and bitumen extracted from the original, as well as from the thermally treated oil shale. Kinetic parameters were determined by assuming a single first-order kinetic model, using the integral method for TG analysis, and ASTM procedure E-698 for d.s.c. analysis. The influence of cracking catalyst addition was examined with respect to the overall kinetics and to conversion in particular temperature regions. Higher values of kinetic parameters were obtained by d.s.c. analysis, and the reasons for the differences between those and the TG results are discussed.