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Model Solutions (model + solution)
Selected AbstractsRHEOLOGICAL PROPERTIES OF CHEMICALLY MODIFIED RICE STARCH MODEL SOLUTIONSJOURNAL OF FOOD PROCESS ENGINEERING, Issue 2 2006C.S. RAINA ABSTRACT Native rice starches have poor resistance to shear, and fair stability to retrogradation with soft texture, which can be altered through chemical modifications. Starch from broken pieces of rice of three rice cultivars (PUSA-44, PR-106 and PR-114) was chemically modified by etherification and esterification reactions by different combinations of modification reagents to investigate the effect of modification on the rheological properties of rice starches. The modification resulted in shear stable gel with apparent pseudoplastic characteristics. The viscosity of starches increased upon acetylation and dual modification as a result of increase in solubility. However, cross-linking had shown the reverse effect. The flow behavior index (n) and consistency coefficient (k) were significantly (P , 0.05) improved upon modification in acetylated and dual-modified starches. The effect of modification on the rheological properties was observed in similar pattern in all the three rice cultivars but varied significantly in variety PUSA-44 may be because of its relatively higher amylose content. [source] THE FOULING AND CLEANING OF ULTRAFILTRATION MEMBRANES DURING THE FILTRATION OF MODEL TEA COMPONENT SOLUTIONSJOURNAL OF FOOD PROCESS ENGINEERING, Issue 3 2007DAN WU ABSTRACT Proteins and polyphenols are the principal fouling constituents in the ultrafiltration (UF) of black tea liquor. The aim of this study was to determine the relative importance of individual components in the fouling process, to investigate any synergetic interactions that were occurring and to compare the cleaning characteristics of different fouled membranes. A 30-kD molecular weight cutoff polysulfone UF membrane in dead-end mode was challenged with model solutions of tea components. Model solutions consisted of tea proteins, theaflavins (TFs), thearubigins and caffeine. Sodium hydroxide was used as a cleaning reagent. Permeate flux decline curves were presented for single components and mixtures. Individual component transfer fluxes and rejections were also presented. An unexpected finding was that protein in a mixture with TFs could permeate the membrane to a degree, while a protein solution in the absence of the polyphenol was completely rejected. The inspection of membranes fouled by different solutions revealed different foulant morphologies. Membrane cleaning with 0.2 wt % sodium hydroxide was generally found to be effective. [source] Solving, Estimating, and Selecting Nonlinear Dynamic Models Without the Curse of DimensionalityECONOMETRICA, Issue 2 2010Viktor Winschel We present a comprehensive framework for Bayesian estimation of structural nonlinear dynamic economic models on sparse grids to overcome the curse of dimensionality for approximations. We apply sparse grids to a global polynomial approximation of the model solution, to the quadrature of integrals arising as rational expectations, and to three new nonlinear state space filters which speed up the sequential importance resampling particle filter. The posterior of the structural parameters is estimated by a new Metropolis,Hastings algorithm with mixing parallel sequences. The parallel extension improves the global maximization property of the algorithm, simplifies the parameterization for an appropriate acceptance ratio, and allows a simple implementation of the estimation on parallel computers. Finally, we provide all algorithms in the open source software JBendge for the solution and estimation of a general class of models. [source] Optimal Monetary Policy with Price and Wage RigiditiesECONOMIC NOTES, Issue 1 2006Massimiliano Marzo In this paper, I search for an optimal configuration of parameters for variants of the Taylor rule by using an accurate second-order welfare-based method within a fully microfounded dynamic stochastic model, with price and wage rigidities, without capital accumulation. A version of the model with distortionary taxation is also explicitly tested. The model is solved up to second-order solution. Optimal rules are obtained by maximizing a conditional welfare measure, differently from what has been done in the current literature. Optimal monetary policy functions turn out to be characterized by inflation targeting parameter lower than in empirical studies. In general, the optimal values for monetary policy parameters depend on the degree of nominal rigidities and on the role of fiscal policy. When nominal rigidities are higher, optimal monetary policy becomes more aggressive to inflation. With a tighter fiscal policy, optimal monetary policy turns out to be less aggressive to inflation. Impulse-response functions based on second-order model solution show a non-affine pattern when the economy is hit by shocks of different magnitude. [source] Electrochemical Detection of Cadmium and Lead Complexes with Low Molecular Weight Organic AcidsELECTROANALYSIS, Issue 3-5 2009Jaklová Dytrtová Abstract The Cd and Pb complexes with oxalic (OA) and citric acid (CA) were detected in model and soil solutions using cyclic and stripping voltammetry. A mixed complex consisting of Cd, Pb, and OA was found; its peak potential varied from ,582.0 to ,542.5,mV (vs. Ag/AgCl/KCl(3,mol L,1)). For mixed complex formation, the presence of PbOH+ species and Cd2+ in oxalic acid solution was necessary. Only the ,simple' complexes of CA with Pb and Cd were found in the model solution. The existence of all investigated metal complexes is confined to neutral pH range. The mixed complex was also found in real soil solutions. [source] Implementation of chemometric methodology in ACE: Predictive investigation of protein,ligand bindingELECTROPHORESIS, Issue 16 2007Grady Hanrahan Abstract An ACE predictive investigation of protein,ligand binding using a highly effective chemometric response surface design technique is presented. Here, Kd was estimated using one noninteracting standard which relates to changes in the electrophoretic mobility of carbonic anhydrase B (CAB, EC 4.2.1.1) on complexation with the ligand 4-carboxybenzenesulfonamide (CBSA) present in the electrophoresis buffer. Experimental factors including injection time, capillary length, and applied voltage were selected and tested at three levels in a Box,Behnken design. Statistical analysis results were used to create a mathematical model for response surface prediction via contour and surface plots at a given target response (Kd,=,1.19×10,6,M). As expected, there were a number of predicted solutions that reached our target response based on the significance of each factor at appropriate levels. The adequacy of the model was validated by experimental runs with the predicted model solution (capillary length,=,47,cm, voltage,=,11,kV, injection time,=,0.01,min) presented in detail as an example. [source] Stochastic analysis of crude oil procurement and processing under uncertain demand for bunker fuel oilINTERNATIONAL TRANSACTIONS IN OPERATIONAL RESEARCH, Issue 5 2006Bernardo Zimberg Abstract Bunker fuel oil (ifo), one of the products of petroleum refining, has a strong impact in the production process because it drives the availability of heavy residues that depend on the crude quality. A simplified stochastic model for the Administración Nacional de Combustibles Alcohol y Portland refinery, based on the uncertainty of the demand for ifo, is proposed for comparison with the current approach of deterministic demand. In this model, the benefits of the production process are maximized, taking decisions on the more suitable raw material, intermediate products and final blends in order to fulfill quality and demand requirements of final products. A specific case is analyzed where the maximum benefit is achieved when the most expensive crude quality is purchased, due to a lack of incentive to produce extra amounts of heavy fuel oil that must be exported at a non-attractive price. Results are compared with the solution of a deterministic model with mean demand. In addition, the stochastic model solution depicts how the refinery should operate for each scenario of ifo demand. [source] Effect of inhibitory compounds on the anaerobic digestion performance of diluted wastewaters from the alimentary industryJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 11 2009Rafael Camarillo Abstract BACKGROUND: Up to now the effect of inhibitory compounds on the anaerobic digestion performance of urban and industrial wastewaters has been mostly studied in fluidized bed and upflowing anaerobic sludge blanket (UASB) bioreactors but not in upflow packed-bed biodigesters. RESULTS: In this paper, response surface methodology (RSM) was used to quantify the effect of various inhibitory compounds (olive oil, ethanol and phenol) on chemical oxygen demand (COD) removal and biogas production rate from synthetic solutions and real industrial wastewaters by anaerobic digestion. The synthetic solutions possessed the same composition in these inhibitory compounds as diluted effluents from olive oil mill and winery industries. The process was performed in a laboratory scale digester containing anaerobic sludge from the Urban Reclamation Station of Toledo (Spain). The comparison of both individual factors and interactions between factors showed that the addition of olive oil at moderate concentrations (up to 0.5% w/w) did not change the performance of the process in comparison with that observed when feeding to the system a model solution (51.5% COD removal, 0.65 L biogas day,1). However, low concentrations of ethanol or phenol (250 and 150 mg L,1, respectively) almost completely inhibited the methanogenic phase. Moreover, a strong interaction between ethanol and phenol concentrations on COD removal was observed. CONCLUSION: The experimental results showed quantitatively the importance of some inhibitory compounds on anaerobic treatment of both synthetic solutions and real wastewaters from olive oil mill and winery industries. Inhibitory effects are closely related to both the organic loads and the anaerobic bioreactor used. Copyright © 2009 Society of Chemical Industry [source] Recovery of Aroma Compounds from Dilute Model Blueberry Solution by PervaporationJOURNAL OF FOOD SCIENCE, Issue 9 2003M. PENG ABSTRACT Pervaporation (PV) is a membrane-separation process showing unique capability of separating target compound(s) from dilute systems. Experiments were performed on a bench-scale flat sheet PV unit with a model solution to evaluate separation factor of 6 constituent aroma compounds (1-hexanol, 1-heptanol, trans-2-hexenal, ethyl acetate, linalool, and d-limonene), representing some of typical flavoring ingredients from blueberry juice. The results showed that separation factor was in the range of 70 to 430, depending on molecule size and polarity property of the compounds. Except for 1-heptanol, all compounds showed no significant coupling effect in the mixture system. The effect of temperature was also examined for a given feed-flow rate. Keywords: pervaporation, membrane, aroma compounds, blueberry, multicomponent diffusion [source] Mechanistic understanding of degradation in bioerodible polymers for drug deliveryAICHE JOURNAL, Issue 12 2002Domenico Larobina A new model was developed to understand the mechanism of erosion in bioerodible polymers, which is essential to accurately predict drug release and precisely design controlled release devices. This model takes into account the phenomenon of microphase separation observed for polyanhydrides of certain copolymer compositions, and assumes that erosion is dominated by degradation and, thus, in a system with a fast eroding and a slow eroding species, two rate constants,one for each species,essentially control the evolution of the polymer microstructure. Expressions were derived for the fraction of each monomer released, as well as for the porosity in the system. A partition coefficient accounts for thermodynamic partitioning of a drug into the microdomains. The solutions of the model equations were fitted to experimental data on monomer release kinetics from two polyanhydride systems to obtain the erosion rate constants. Drug release kinetics experiments are compared to the model solution for drug release, and the partition coefficient of the drug is obtained from the fits. The comparisons to the data are promising, while pointing out the limitations of the model. The model does not account for oligomer formation prior to monomer release or for the dependence of the rate constants on parameters such as the degree of crystallinity, the local pH, and the polymer molecular weight. [source] MODELING OF SWEET, BITTER AND IRRITANT SENSATIONS AND THEIR INTERACTIONS ELICITED BY MODEL ICE WINESJOURNAL OF SENSORY STUDIES, Issue 5 2006CANAN NURGEL ABSTRACT Interactions between taste and irritant sensations elicited by model ice wine solutions were investigated, including the use of U and ,, models for predicting the perceived intensity of these sensory interactions. Fifteen solutions of varying ethanol and sugar concentrations representative of commercial ice wine values were evaluated in two trials by a trained sensory panel (n = 12) for perceived sweetness, bitterness and heat intensities. Sweetness perception of lower sugar-concentration level in ice wine model solution was affected by ethanol concentration. The sweetness intensities of the sugar and ethanol mixtures are higher than the sweetness intensities of sugar solutions. The ,, index indicates a slight synergy between ethanol and sugar on sweetness perception. The bitterness intensities elicited by ethanol,sugar mixtures are lower than those elicited by unmixed ethanol solutions. The ,, index indicates inhibition of ethanol and sugar perception on bitterness perception. Suppression of heat sensation was found in model base wine solutions across sugar and ethanol concentrations. [source] A kinetic study of the reactions of (+)-catechin with aldehydes derived from toasted oakJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 11 2007Marie-Françoise Nonier Abstract The reactions between (+)-catechin and representative oak wood furanic (furfuraldehyde, 5-hydroxymethylfurfuraldehyde and 5-methylfurfuraldehyde) and phenolic (vanillin and syringaldehyde) aldehydes in a wine-like model solution were studied and the corresponding condensation kinetics at pH 3.0 and 3.5 were compared. A comparative study on the reactivity of these two representative families of aldehydes towards (+)-catechin showed a large difference between them. When incubated separately with (+)-catechin at both pH values, the reactions were faster with furanic aldehydes than with phenolic aldehydes. In mixtures containing (+)-catechin and individual aldehydes, new compounds were identified by high-performance liquid chromatography (HPLC)/UV,visible detection, some of which were characterised by liquid chromatography/electrospray ionisation mass spectrometry (LC/ESI-MS). The increase in solution absorbance with time was closely linked to these new products. Copyright © 2007 Society of Chemical Industry [source] Balanced boundary layers used in hurricane modelsTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 635 2008Roger K. Smith Abstract We examine the formulation and accuracy of various approximations made in representing the boundary layer in simple axisymmetric hurricane models, especially those that assume strict gradient wind balance in the radial direction. Approximate solutions for a steady axisymmetric slab boundary-layer model are compared with a full model solution. It is shown that the approximate solutions are generally poor in the inner core region of the vortex, where the radial advection term in the radial momentum equation is important and cannot be neglected. These results affirm some prior work and have implications for a range of theoretical studies of hurricane dynamics, including theories of potential intensity, that employ balanced boundary-layer formulations. Copyright © 2008 Royal Meteorological Society [source] Phenol Removal through Chemical Oxidation using Fenton ReagentCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 5 2007Y. Yavuz Abstract In this study, phenol, aromatic, and non-biodegradable organic matter were investigated and found to be removed from the model solution through chemical oxidation using Fenton reagent. The effects of the initial phenol concentration, hydrogen peroxide, and ferrous sulfate concentrations on the removal efficiency were investigated. Performance of the chemical oxidation process was monitored with phenol and COD (Chemical Oxygen Demand) analyses. In the experimental studies, phenol removal of over 98,% and COD removal of nearly 70,% were achieved. The optimum conditions for Fenton reaction both for initial phenol concentrations of 200 and 500,mg/L were found at a ratio [Fe2+]/[H2O2] (mol/mol) equal to 0.11. According to the results, chemical oxidation using Fenton reagent was found to be too effective, especially for phenol removal. However, this method has limited removal efficiency for COD. [source] Kinetics and Mechanism of Ni(II) Chelation in Model and Real Solutions of Xylem Sap of Quercus ilexELECTROANALYSIS, Issue 22 2007Margarida, Maria Correia, Santos Abstract The kinetics of formation and dissociation of Ni(II) complexes with oxalic and citric acids was studied by cyclic voltammetry in model solutions of xylem sap of Q. ilex (the dominant tree growing on serpentine soils of Northeast Portugal) using representative concentrations, pH and ionic strength. The role of magnesium on complex formation was analyzed from solutions where Mg is present at concentration levels found in the xylem sap of Q. ilex growing on both nonserpentine and serpentine soils. Kinetics studies were also done in diluted solutions of real xylem sap samples, spiked with increasing amounts of magnesium. The values obtained for the apparent rate constants were those anticipated by the proposed model. To test the validity of the methodology and mechanisms, formation rate constants, kf (M,1 s,1) of Ni(II) complexes with citrate and oxalate were evaluated that compare with the values from Eigen mechanism. [source] Cross-cultural assessment of eating disorders: psychometric properties of a Spanish version of the Bulimia Test-Revised,EUROPEAN EATING DISORDERS REVIEW, Issue 6 2007Mayra N. Berrios-Hernandez Abstract The purpose of this study was to examine the psychometric properties of a Spanish version of the Bulimia Test-Revised (BULIT-R). The goal was to test the factor-structure equivalence of the BULIT-R across two samples of college students from two different cultures, Spain and the US. Researchers using exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) have reported different model solutions for the factor-structure of the BULIT-R: a one-factor model, a four-factor model, a five-factor model and a six-factor model. For the two samples, CFA did not support any of the models previously reported in the literature. EFA supported a six- and a four-factor models for the US and Spanish samples, respectively. © 2007 John Wiley & Sons, Ltd and Eating Disorders Association. [source] Impact of Simulation Model Solver Performance on Ground Water Management ProblemsGROUND WATER, Issue 5 2008David P. Ahlfeld Ground water management models require the repeated solution of a simulation model to identify an optimal solution to the management problem. Limited precision in simulation model calculations can cause optimization algorithms to produce erroneous solutions. Experiments are conducted on a transient field application with a streamflow depletion control management formulation solved with a response matrix approach. The experiment consists of solving the management model with different levels of simulation model solution precision and comparing the differences in optimal solutions obtained. The precision of simulation model solutions is controlled by choice of solver and convergence parameter and is monitored by observing reported budget discrepancy. The difference in management model solutions results from errors in computation of response coefficients. Error in the largest response coefficients is found to have the most significant impact on the optimal solution. Methods for diagnosing the adequacy of precision when simulation models are used in a management model framework are proposed. [source] Optimization of ingredients for the formulation of a direct acidified whey based lassi-like beverageINTERNATIONAL JOURNAL OF DAIRY TECHNOLOGY, Issue 2 2008KALYANI NAIR Samples of direct acidified whey based lassi like beverage were prepared with different proportions of guar gum, CMC and inulin and were examined for sensory and physical attributes. The optimisation was carried out using central composite rotatory design (CCRD) of response surface methodology (RSM). Response surface analysis revealed that sensory scores for flavour, consistency, colour and appearance and overall acceptability of lassi like beverage varied from 6.50 to 7.25, 6.16 to 7.12, 6.20 to 7.41 and 5.96 to 7.20 respectively. The results of analysis showed that all the examined model solutions had significant influence on the different parameters indicating that the statistical model designed for these attributes fitted well in all the aspects of model efficiency check (R2 >85%). [source] Multiplicative random regression model for heterogeneous variance adjustment in genetic evaluation for milk yield in SimmentalJOURNAL OF ANIMAL BREEDING AND GENETICS, Issue 3 2008M.H. Lidauer Summary A multiplicative random regression (M-RRM) test-day (TD) model was used to analyse daily milk yields from all available parities of German and Austrian Simmental dairy cattle. The method to account for heterogeneous variance (HV) was based on the multiplicative mixed model approach of Meuwissen. The variance model for the heterogeneity parameters included a fixed region × year × month × parity effect and a random herd × test-month effect with a within-herd first-order autocorrelation between test-months. Acceleration of variance model solutions after each multiplicative model cycle enabled fast convergence of adjustment factors and reduced total computing time significantly. Maximum Likelihood estimation of within-strata residual variances was enhanced by inclusion of approximated information on loss in degrees of freedom due to estimation of location parameters. This improved heterogeneity estimates for very small herds. The multiplicative model was compared with a model that assumed homogeneous variance. Re-estimated genetic variances, based on Mendelian sampling deviations, were homogeneous for the M-RRM TD model but heterogeneous for the homogeneous random regression TD model. Accounting for HV had large effect on cow ranking but moderate effect on bull ranking. [source] THE FOULING AND CLEANING OF ULTRAFILTRATION MEMBRANES DURING THE FILTRATION OF MODEL TEA COMPONENT SOLUTIONSJOURNAL OF FOOD PROCESS ENGINEERING, Issue 3 2007DAN WU ABSTRACT Proteins and polyphenols are the principal fouling constituents in the ultrafiltration (UF) of black tea liquor. The aim of this study was to determine the relative importance of individual components in the fouling process, to investigate any synergetic interactions that were occurring and to compare the cleaning characteristics of different fouled membranes. A 30-kD molecular weight cutoff polysulfone UF membrane in dead-end mode was challenged with model solutions of tea components. Model solutions consisted of tea proteins, theaflavins (TFs), thearubigins and caffeine. Sodium hydroxide was used as a cleaning reagent. Permeate flux decline curves were presented for single components and mixtures. Individual component transfer fluxes and rejections were also presented. An unexpected finding was that protein in a mixture with TFs could permeate the membrane to a degree, while a protein solution in the absence of the polyphenol was completely rejected. The inspection of membranes fouled by different solutions revealed different foulant morphologies. Membrane cleaning with 0.2 wt % sodium hydroxide was generally found to be effective. [source] DEGRADATION KINETICS OF ANTHOCYANIN IN ETHANOLIC SOLUTIONSJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 5 2006KUO-CHAN TSENG ABSTRACT The objective of this study was to investigate the degradation kinetics of anthocyanin in ethanolic model solutions simulating wine and liqueur in aging or long-term storage. Malvidin-3-glucoside, as the predominant anthocyanin in many cultivars of grape, was chosen to represent anthocyanins. The results from high performance liquid chromatography analysis show that the disappearance of malvidin-3-glucoside follows apparent first-order kinetics, and accelerates with the increase in ethanol concentration. The Ea values were found to be 22.80, 24.45, 24.35 and 22.75 kcal/mole at 0, 10, 30 and 50% ethanol concentrations, respectively. We propose that the decreased stability of anthocyanin at an elevated ethanol concentration is a result of a decreased extent of self-association in the solution. [source] Extraction of propionic acid from model solutions: Effect of pH, salts, substrate, and temperatureAICHE JOURNAL, Issue 7 2009Amit Keshav Abstract Propionic acid can be successfully produced from fermentation broth once an efficient recovery method is available for the produced acid. Reactive extraction in this regard is a promising recovery method. pH, salt, substrate, and temperature studies are crucial in the extraction of propionic acid, because these parameters varied in actual fermentation broth. With this regard, effects of these were studied. Extraction from model solutions and salt or substrate containing systems is lower than what was obtained from normal aqueous solutions. Reason of this is the varying degree of hindrances of the salts on extraction of the acid. pH has very large effect on extraction efficiency of the extracting system. At pH > pKa of acid, very low extraction was obtained. Temperature was found to have no effect on the extraction from model solutions used. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Determination of cyprodinil and fludioxonil in the fermentative process of must by high-performance liquid chromatography,diode array detectionJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 11 2008Luis Vaquero-Fernández Abstract BACKGROUND: A quantitative, selective and sensitive high-performance liquid chromatographic method is described for the analysis of new fungicides cyprodinil, fludioxonil and their commercial formulation Switch in model solutions of must and wine, as well as samples during alcoholic fermentation. A study of the dissipation of residues was carried out. RESULTS: The proposed method is based on liquid,liquid extraction (LLE) followed by high-performance liquid chromatography and diode array detection. Dichloromethane was the most appropriate solvent for extracting cyprodinil and fludioxonil in samples. Quality parameters of the proposed method presented good recovery (ca. 97% for almost all compounds) and precision (between 4.8% and 5.4%), and limits of quantification were lower than maximum residue limits (MRLs) in grapes. CONCLUSIONS: There is no matrix effect in the analysis of cyprodinil and fludioxonil. The application of the fermentative process on cyprodinil and fludioxonil fungicides causes a decrease in the concentrations of these compounds. This decrease is slightly higher, the higher the initial concentration, without observing the appearance of any product in degradation. Fludioxonil shows a higher reduction when the compounds are presented together in Switch. Copyright © 2008 Society of Chemical Industry [source] Inhibition of browning by antibrowning agents and phenolic acids or cinnamic acid in the glucose,lysine modelJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 8 2005Eun-Jung Kwak Abstract The effects of antibrowning agents and phenolic acids or cinnamic acid on the inhibition of browning were investigated with a glucose,lysine model. Six antibrowning agents (cysteine, glutathione, sodium sulfite, pentasodium tripolyphosphate, citric acid and oxalic acid) and four phenolic acids (ferulic, hydroxybenzoic, syringic and vanillic acids) were used. In order to investigate the antibrowning capacity of these agents, model solutions containing glucose, lysine and an antibrowning agent were heated at 50 °C in the presence of FeCl2, before being stored in nitrogen or air at 4 °C or 30 °C. Browning was accelerated to some degree during storage in air at 30 °C. In the case of storage at 4 °C, however, no browning was detected in nitrogen after four weeks. Citric acid was the most efficient antibrowning agent during storage in air at 30 °C and inhibited browning to 36% after four weeks. However, its antibrowning capacity was increased by 8,15% in the presence of any of the phenolic acids or cinnamic acid, essentially independently of concentration in the range 10 µM to 10 mM or the type of phenolic acid. Copyright © 2005 Society of Chemical Industry [source] Detection of phenolic oxidation products in cider apple juice by high-performance liquid chromatography electrospray ionisation ion trap mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 9 2004S. Bernillon Juice was prepared from cider apples of the cultivar "Kermerrien" under oxidative conditions. After isolation by solid-phase extraction, the phenolic fraction was subjected to high-performance liquid chromatography/electrospray ionisation mass spectrometry. SIM scans were performed at m/z values obtained in model solutions. The oxidation products, resulting from coupling between a molecule of caffeoylquinic acid and caffeoylquinic acid, catechin or dimeric flavan-3-ol, were detected. Copyright © 2004 John Wiley & Sons, Ltd. [source] Recovery and separation of cell lysate proteins using hydrogels guided by aqueous two-phase extraction principlesBIOTECHNOLOGY & BIOENGINEERING, Issue 2 2002Christopher S. Putka Abstract The addition of poly(ethylene glycol) and salts to clarified cell lysates of Thiosphaera pantotropha increases sorption of microbial proteins into dextran hydrogels, consistent with the thermodynamics of aqueous two-phase extraction. Addition of 12 wt% PEG-10,000 to the lysate increased total sorption of protein by the dextran gel from 5.2 mg/g dextran to 37 mg/g; addition of either 0.1 M potassium iodide or tetrabutylammonium fluoride along with PEG to the lysate increased protein sorption to more than 63 mg/g, a 12-fold increase. SDS-PAGE demonstrated that the type of salt added controls which proteins are absorbed by the gel. Previously demonstrated only with model solutions, these results suggest another approach to recovery and separation strategies for proteins produced by fermentation. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 80: 139,143, 2002. [source] Prediction of ice content in biological model solutions when frozen under high pressureBIOTECHNOLOGY PROGRESS, Issue 2 2009B. Guignon Abstract High pressure is, at least, as effective as cryoprotective agents (CPAs) and are used for decreasing both homogenous nucleation and freezing temperatures. This fact gives rise to a great variety of possible cryopreservation processes under high pressure. They have not been optimized yet, since they are relatively recent and are mainly based on the pressure,temperature phase diagram of pure water. Very few phase diagrams of biological material are available under pressure. This is owing to the lack of suitable equipment and to the difficulties encountered in carrying out the measurements. Different aqueous solutions of salt and CPAs as biological models are studied in the range of 0°C down to -35°C, 0.1 up to 250 MPa, and 0,20% w/w total solute concentration. The phase transition curves of glycerol and of sodium chloride with either glycerol or sucrose in aqueous solutions are determined in a high hydrostatic pressure vessel. The experimental phase diagrams of binary solutions were well described by a third-degree polynomial equation. It was also shown that Robinson and Stokes' equation at high pressure succeeds in predicting the phase diagrams of both binary and ternary solutions. The solute cryoconcentration and the ice content were calculated as a function of temperature and pressure conditions during the freezing of a binary solution. This information should provide a basis upon which high-pressure cryopreservation processes may be performed and the damages derived from ice formation evaluated. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] Surfactant Effects on Aeration Performance of Stirred Tank ReactorsCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 10 2008M. Martinov Abstract The effect of surfactants on aeration performance in stirred tank reactors (STR) at high rates of foaming is studied. The volumetric oxygen transfer coefficient (kLa) and foaming activity estimated as foaming height (Hf) were determined. Biotechnology of lipopeptide biosurfactants from aerobic organisms, e.g., Bacillus subtilis were addressed. Using model solutions of known foam-generating properties, high-molecular weight surfactin and low-molecular weight sodium dodecyl sulphate (SDS), as well as impellers of different types, with flat and fluid-foil blades, clues on the concentration dependence of STR oxygen transfer and foaming as well as options for foam reduction in the presence of biosurfactant were sought. In response to a two-fold decrease of surface tension by surfactin, kLa values decreased up to 30,% but remained within the range expected for the mixing system in water; the experiments with SDS showing stronger dependence on surfactant concentration and surface tension. Mixing of surfactant media by a standard six-blade disc turbine (RT) imposed rate limitations on gassing. A low-shear impeller Narcissus (NS) could be used to avoid bulk foam outflow, while preserving kLa values that remained unchanged. The ,power per unit volume' correlation of kLa in stirred tanks is tested in the presence of surfactin. [source] | |||||||||||||||||||||||||||||||