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RSM
Selected AbstractsUse of chemometric methodology in optimizing conditions for competitive binding partial filling affinity capillary electrophoresisELECTROPHORESIS, Issue 16 2008Ruth E. Montes Abstract This work expands the knowledge of the use of chemometric response surface methodology (RSM) in optimizing conditions for competitive binding partial filling ACE (PFACE). Specifically, RSM in the form of a Box,Behnken design was implemented in flow-through PFACE (FTPFACE) to effectively predict the significance of injection time, voltage, and neutral ligand (neutral arylsulfonamide) concentration, [Lo], on protein,neutral ligand binding. Statistical analysis results were used to create a model for response surface prediction via contour and surface plots at a given maximum response (,RMTR) to reach a targeted Kb,=,2.50×106,M,1. The adequacy of the model was then validated by experimental runs at the optimal predicted solution (injection time,=,2.3,min, voltage,=,11.6,kV, [Lo],=,1.4,,M). The achieved results greatly extend the usefulness of chemometrics in ACE and provide a valuable statistical tool for the study of other receptor,ligand combinations. [source] Antioxidant capacity of rapeseed meal and rapeseed oils enriched with meal extractEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 7 2010Aleksandra Szyd, owska-Czerniak Abstract Response surface methodology (RSM) was used to evaluate the quantitative effects of two independent variables: solvent polarity and temperature of the extraction process on the antioxidant capacity (AC) and total phenolics content (TPC) in meal rapeseed extracts. The mean AC and TPC results for meal ranged between 1181,9974,µmol TE/100,g and 73.8,814,mg sinapic acid/100,g of meal. The experimental results of AC and TPC were close to the predicted values calculated from the polynomial response surface models equations (R2,=,0.9758 and 0.9603, respectively). The effect of solvent polarity on AC and TPC in the examined extracts was about 3.6 and 2.6 times greater, respectively, than the effect of processing temperature. The predicted optimum solvent polarity of ,,=,78.3 and 63.8, and temperature of 89.4 and 74.2°C resulted in an AC of 10,014,µmol TE/100,g and TPC of 863,mg SAE/100,g meal, respectively. The phenolic profile of rapeseed meal was determined by an HPLC method. The main phenolics in rapeseed meal were sinapine and sinapic acid. Refined rapeseed oils were fortified with an extract , rich in polyphenols , obtained from rapeseed meal. The supplemented rapeseed oil had higher AC and TPC than the refined oil without addition of meal extracts. However, AC and TPC in the enriched oils decreased during storage. The TPC in the studied meal extracts and rapeseed oils correlated significantly (p<0.0000001) positively with their AC (R2,=,0.9387). Practical applications: Many bioactive compounds extracted from rapeseed meal provide health benefits and have antioxidative properties. Therefore, it seems worth to consider the application of antioxidants extracted from the rapeseed meal for the production of rapeseed oils with potent AC. Moreover, antioxidants extracted from the rapeseed meal were added to refined rapeseed oil in order to enhance its AC. AC was then tested by FRAP assay. FRAP method is based on the reduction of the ferric tripyridyltriazine (Fe3+ -TPTZ) complex to the ferrous tripyridyltriazine (Fe2+ -TPTZ), and it is simple, fast, low cost, and robust method. FRAP method does not require specialized equipment and can be performed using automated, semi-automatic, or manual methods. Therefore the proposed FRAP method can be employed by the fat industry laboratories to asses the AC of rapeseed oils and meal. [source] The Role of Strain in New Semiconductor DevicesADVANCED ENGINEERING MATERIALS, Issue 4 2009Alex Dommann HRXRD is a very sensitive and non destructive technique to determine the strain in thin layer materials such as electron guides or the strain induces by the second order package of SOCs. In reciprocal space mapping (RSM), it is possible to separate the elastic component of the scattered intensity from the diffuse one. As a consequence, it is possible to study diffuse scattering due to defects of the crystal lattice. As an example we show also RSM's of a high-speed SiGe pMOS structure. [source] Multi-objective turbomachinery optimization using a gradient-enhanced multi-layer perceptronINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 6 2009M. C. Duta Abstract Response surface models (RSMs) have found widespread use to reduce the overall computational cost of turbomachinery blading design optimization. Recent developments have seen the successful use of gradient information alongside sampled response values in building accurate response surfaces. This paper describes the use of gradients to enhance the performance of the RSM provided by a multi-layer perceptron. Gradient information is included in the perceptron by modifying the error function such that the perceptron is trained to fit the gradients as well as the response values. As a consequence, the back-propagation scheme that assists the training is also changed. The paper formulates the gradient-enhanced multi-layer perceptron using algebraic notation, with an emphasis on the ease of use and efficiency of computer code implementation. To illustrate the benefit of using gradient information, the enhanced neural network model is used in a multi-objective transonic fan blade optimization exercise of engineering relevance. Copyright © 2008 John Wiley & Sons, Ltd. [source] Comparative study of the continuous phase flow in a cyclone separator using different turbulence models,INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 11 2005H. Shalaby Abstract Numerical calculations were carried out at the apex cone and various axial positions of a gas cyclone separator for industrial applications. Two different NS-solvers (a commercial one (CFX 4.4 ANSYS GmbH, Munich, Germany, CFX Solver Documentation, 1998), and a research code (Post-doctoral Thesis, Technical University of Chemnitz, Germany, September, 2002)) based on a pressure correction algorithm of the SIMPLE method have been applied to predict the flow behaviour. The flow was assumed as unsteady, incompressible and isothermal. A k,, turbulence model has been applied first using the commercial code to investigate the gas flow. Due to the nature of cyclone flows, which exhibit highly curved streamlines and anisotropic turbulence, advanced turbulence models such as Reynolds stress model (RSM) and large eddy simulation (LES) have been used as well. The RSM simulation was performed using the commercial package activating the Launder et al.'s (J. Fluid. Mech. 1975; 68(3):537,566) approach, while for the LES calculations the research code has been applied utilizing the Smagorinsky model. It was found that the k,, model cannot predict flow phenomena inside the cyclone properly due to the strong curvature of the streamlines. The RSM results are comparable with LES results in the area of the apex cone plane. However, the application of the LES reveals qualitative agreement with the experimental data, but requires higher computer capacity and longer running times than RSM. This paper is organized into five sections. The first section consists of an introduction and a summary of previous work. Section 2 deals with turbulence modelling including the governing equations and the three turbulence models used. In Section 3, computational parameters are discussed such as computational grids, boundary conditions and the solution algorithm with respect to the use of MISTRAL/PartFlow-3D. In Section 4, prediction profiles of the gas flow at axial and apex cone positions are presented and discussed. Section 5 summarizes and concludes the paper. Copyright © 2005 John Wiley & Sons, Ltd. [source] Calculation of turbulent fluid flow and heat transfer in ducts by a full Reynolds stress modelINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 2 2003Masoud Rokni Abstract A computational method has been developed to predict the turbulent Reynolds stresses and turbulent heat fluxes in ducts by different turbulence models. The turbulent Reynolds stresses and other turbulent flow quantities are predicted with a full Reynolds stress model (RSM). The turbulent heat fluxes are modelled by a SED concept, the GGDH and the WET methods. Two wall functions are used, one for the velocity field and one for the temperature field. All the models are implemented for an arbitrary three-dimensional channel. Fully developed condition is achieved by imposing cyclic boundary conditions in the main flow direction. The numerical approach is based on the finite volume technique with a non-staggered grid arrangement. The pressure,velocity coupling is handled by using the SIMPLEC-algorithm. The convective terms are treated by the van Leer scheme while the diffusive terms are handled by the central-difference scheme. The hybrid scheme is used for solving the , equation. The secondary flow generation using the RSM model is compared with a non-linear k,, model (non-linear eddy viscosity model). The overall comparison between the models is presented in terms of the friction factor and Nusselt number. Copyright © 2003 John Wiley & Sons, Ltd. [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] Recovery of rat submandibular salivary gland function following removal of obstruction: a sialometrical and sialochemical studyINTERNATIONAL JOURNAL OF EXPERIMENTAL PATHOLOGY, Issue 6 2006Samira M. Osailan Summary Functional recovery of the rat submandibular gland following ligation of the main excretory duct was examined. Rat submandibular glands were ligated for 1, 4 and 8 weeks using a micro-clip with a plastic tube. Micro-clips were removed and glands were allowed to recover for periods of 8, 16 and 24 weeks. Submandibular glands were stimulated with autonomimetic drugs (methacholine and isoprenaline) and salivas were collected from atrophic or de-ligated and contralateral control glands. Glands recovered almost full size (92% of control gland) following 24 weeks of de-ligation. Saliva volume secreted by ligated/de-ligated (RSM) and control (LSM) glands were similar with different doses of agonists. Protein output expressed per gram of tissue wet weight was similar from both ligated/de-ligated and control glands with all doses of agonist. Sodium and chloride levels were higher from de-ligated glands than contralateral control glands. Protein electrophoresis showed similar profiles of salivary proteins in all samples with some minor differences. Acinar cells in de-ligated glands showed a normal morphology, as indicated by light microscopy, whilst granular ductal cells were fewer and contained fewer secretory granules. Sodium potassium ATPase staining of striated ducts in de-ligated glands was similar to that of control glands. It can be concluded that rat submandibular glands can regenerate following severe atrophy and secrete normal amounts of saliva containing broadly a full profile of secretory proteins. In contrast to acinar cells, ductal cells appear not to recover full function. [source] Review article: Basic steps in adapting response surface methodology as mathematical modelling for bioprocess optimisation in the food systemsINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 9 2010Titus U. Nwabueze Summary Techniques involving choosing process combinations for optimisation without due consideration for relevant experimental designs is scientifically unreliable and irreproducible. Mathematical modelling, of which response surface methodology (RSM) is one, provides a precise map leading to successful optimisation. This paper identified key process variables, building the model and searching the solution through multivariate regression analysis, interpretation of resulting polynomial equations and response surface/contour plots as basic steps in adapting the central composite design to achieve process optimisation. It also gave information on appropriate RSM software packages and choice of order in RSM model and data economy in reducing the factorial experiments from large number parameter combinations to a far less number without losing any information including quadratic and interaction (if present) effects. It is expected that this paper will afford many food scientists and researchers the opportunity for adapting RSM as a mathematical model for achieving bioprocess optimisation in food systems. [source] The effect of low-temperature blanching on the quality of fresh and frozen/thawed mashed potatoesINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 5 2006Cristina Fernández Summary The effect of low-temperature blanching (LTB) prior to cooking on colour, textural, firmness and oscillatory parameters, sensory attributes and overall acceptability of either fresh or frozen/thawed mashed potatoes was studied using response surface methodology (RSM) to establish the optimum temperature and time for blanching in both types of mashed potatoes. A central composite rotatable design was used to study the effects of variation in levels of blanching temperature (57.93,72.07 °C) and time (15.86,44.14 min) on the quality parameters. Stationary points showing maximum thickening had critical temperatures (approximately 67,69 °C) and times (approximately 26,30 min) in the ranges of temperature and time used for each independent variable for both fresh and frozen/thawed mashed potato. Results showed a high correlation between structural reinforcement and overall acceptability under optimum experimental blanching conditions. This demonstrates the potential of this experimental approach in terms of tailoring physical properties to predetermined levels in order to meet consumer preferences in mashed potatoes, and of altering the changes that occur after freezing and thawing. [source] Two-stage computing budget allocation approach for the response surface methodINTERNATIONAL TRANSACTIONS IN OPERATIONAL RESEARCH, Issue 6 2007J. Peng Abstract Response surface methodology (RSM) is one of the main statistical approaches to search for an input combination that optimizes the simulation output. In the early stages of RSM, an iterative steepest ascent search procedure is frequently used. In this paper, we attempt to improve this procedure by considering a more realistic case where there are computing budget constraints, and formulate a new computing budget allocation problem to look into the important issue of allocating computing budget to the design points in the local region of experimentation. We propose a two-stage computing budget allocation approach, which uses a limited budget to estimate the response surface in the first stage and then uses the rest of the budget to improve the lower bound of the estimated response at the center of the next design region in the second stage. Several numerical experiments are carried out to compare the two-stage approach with the regular factorial design, which allocates budget equally to each design point. The results show that our two-stage allocation outperforms the equal allocation, especially when the system noise is large. [source] Response surface methodology to optimize the nutritional parameters for enhanced production of jasmonic acid by Lasiodiplodia theobromaeJOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2008P.C. Dhandhukia Abstract Aims:, To find out the cumulative effect of the nutritional parameters and to enhance the production of jasmonic acid (JA) in static fermentation by Lasiodiplodia theobromae using response surface methodology (RSM). Method and Results:, Malt extract, sucrose, NaNO3 and MgSO4.7H2O were analysed by a 30-trial central composite design using RSM for optimizing their concentrations in the medium and the effect of their mutual interaction on JA production. Sucrose and NaNO3 were found highly significant in influencing the JA production. Malt extract and MgSO4.7H2O showed an effect on the JA production in interaction with other variables. When the optimum values of the parameters obtained through RSM (19·95 g l,1 malt extract, 50 g l,1 sucrose, 7·5 g l,1 NaNO3 and 3·51 g l,1 MgSO4.7H2O) were applied, 32% increase in JA production (299 mg l,1) was observed in comparison with 225 mg l,1 of JA produced with same media components not analysed by RSM and subsequently validated the statistical model. Conclusions:, Increase in JA production was achieved by optimizing the nutritional parameters. Significance and Impact of the Study:, This is the first report of using RSM for optimizing a medium for JA production. It resulted in an increase in JA production without augmentation of costly additives. [source] Optimization of a medium for enhancing nicotine biodegradation by Ochrobactrum intermedium DN2JOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2006Y.J. Yuan Abstract Aims:, To optimize a medium for nicotine degradation by Ochrobactrum intermedium DN2 in presence of yeast extract, glucose and Tween 80 using response surface methodology (RSM). Methods and Results:, In this study, the effects of yeast extract, glucose and Tween 80 on nicotine degradation were investigated in flasks using a novel nicotine-degrading bacterium, O. intermedium DN2. A full factorial central composite design was applied in the design of experiments and in the analysis of the experimental data. The results showed that the most significant variable influencing nicotine degradation was yeast extract, followed by glucose, and then Tween 80. Moreover these three factors interacted with each other and combined to produce positive effects on nicotine degradation. The experimental data also allowed the development of an empirical model (P < 0·0001) describing the inter-relationship between independent and dependent variables. By solving the regression equation, the optimal values of the variables were determined as: yeast extracts 0·094%, glucose 0·101% and Tween 80 0·080%. Using the medium obtained, about 1220 mg l,1 of nicotine was degraded (95·55%) within 10 h at the specific biodegradation of 116·59 mg l,1 h,1 in 30-l bioreactor containing 25-l tobacco extract. Conclusions:, An optimal medium of nicotine degradation by the strain DN2 was obtained. Significance and Impact of the Study:, RSM proved to be reliable in developing the model, optimizing factors and analysing interaction effects. The results provide better understanding on the interactions between yeast extract, glucose and Tween 80 for nicotine biodegradation. [source] Use of sweet sorghum juice for lactic acid fermentation: preliminary steps in a process optimizationJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 6 2010Kata Hetényi Abstract BACKGROUND: Lactic acid has many applications in the chemical industries and it can be produced economically by microorganisms using biomass raw materials of different origins. Sweet sorghum juice is a high sugar content raw material with potential for lactic acid production because after hydrolysis of its sucrose content the remaining glucose and fructose can supply the carbon demand of most lactic acid bacteria. However, satisfying the nitrogen and B-vitamin needs of the bacteria by supplementation with yeast extract and/or other alternative nitrogen-containing supplements can make the process too expensive. RESULTS: Using a statistical optimization process much of the yeast extract can be replaced by a cheaper alternative nitrogen source, namely wheat gluten. This resulted in a fermentation with 99% lactic acid yield and 3.04 g L,1 h,1 volumetric productivity. CONCLUSION: Using response surface methodology (RSM) media optimization was performed for lactic acid fermentation with an industrially acceptable result, reducing the costs of raw materials by half, replacing yeast extract by an alternative nitrogen source and applying yeast extract only as a source of micro-elements (vitamins, salts, etc.) Copyright © 2010 Society of Chemical Industry [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] Optimization and analysis of nickel adsorption on microwave irradiated rice husk using response surface methodology (RSM)JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 2 2009Magesh Ganesa Pillai Abstract BACKGROUND: The removal of heavy metals using adsorption techniques with low cost biosorbents is being extensively investigated. The improved adsorption is essentially due to the pores present in the adsorbent. One way of improving the porosity of the material is by irradiation of the precursor using microwaves. In the present study, the adsorption characteristics of nickel onto microwave-irradiated rice husks were studied and the process variables were optimized through response surface methodology (RSM). RESULT: The adsorption of nickel onto microwave-irradiated rice husk (MIRH) was found to be better than that of the raw rice husk (RRH). The kinetics of the adsorption of Ni(II) from aqueous solution onto MIRH was found to follow a pseudo-second-order model. Thermodynamic parameters such as standard Gibbs free energy (,G°), standard enthalpy (,H°), and standard entropy (,S°) were also evaluated. The thermodynamics of Ni(II) adsorption onto MIRH indicates that it is spontaneous and endothermic in nature. The response surface methodology (RSM) was employed to optimize the design parameters for the present process. CONCLUSION: Microwave-irradiated rice husk was found to be a suitable adsorbent for the removal of nickel(II) ions from aqueous solutions. The adsorption capacity of the rice husk was found to be 1.17 mg g,1. The optimized parameters for the current process were found as follows: adsorbent loading 2.8 g (100 mL),1; Initial adsorbate concentration 6 mg L,1; adsorption time 210 min.; and adsorption temperature 35 °C. Copyright © 2008 Society of Chemical Industry [source] Lipase-catalyzed ethanolysis of soybean oil in a solvent-free system using central composite design and response surface methodologyJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 6 2008Rafael Costa Rodrigues Abstract BACKGROUND: In this work we describe the synthesis of ethyl esters, commonly known as biodiesel, using refined soybean oil and ethanol in a solvent-free system catalyzed by lipase from Thermomyces lanuginosus. Central composite design and response surface methodology (RSM) were employed to optimize the biodiesel synthesis parameters, which were: reaction time, temperature, substrate molar ratio, enzyme content, and added water, measured as percentage of yield conversion. RESULTS: The optimal conditions obtained were: temperature, 31.5 °C; reaction time, 7 h; substrate molar ratio, 7.5:1 ethanol:soybean oil; enzyme content, 15% (g enzyme g,1 oil); added water, 4% (g water g,1 oil). The experimental yield conversion obtained under these conditions was 96%, which is very close to the maximum predicted value of 94.4%. The reaction time-course at the optimal values indicated that 5 h was necessary to obtain high yield conversions. CONCLUSION: A high yield conversion was obtained under the optimized conditions, with relative low enzyme content and short time. Comparison of predicted and experimental values showed good correspondence, implying that the empirical model derived from RSM can be used to adequately describe the relationship between the reaction parameters and the response (yield conversion) in lipase-catalyzed biodiesel synthesis. Copyright © 2008 Society of Chemical Industry [source] Lipase-mediated methanolysis of soybean oils for biodiesel productionJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 1 2008Xin Chen Abstract BACKGROUND: Biodiesel is increasingly perceived as an important component of solutions to the important current issues of fossil fuel shortages and environmental pollution. Biocatalysis of soybean oils using soluble lipase offers an alternative approach to lipase-catalyzed biodiesel production using immobilized enzyme or whole-cell catalysis. The central composite design (CCD) of response surface methodology (RSM) was used here to evaluate the effects of enzyme concentration, temperature, molar ratio of methanol to oil and stirring rate on the yield of fatty methyl ester. RESULTS: Lipase NS81006 from a genetically modified Aspergillus oryzae was utilized as the catalyst for the transesterification of soybean oil for biodiesel production. The experimental data showed that enzyme concentration, molar ratio of methanol to oil and stirring rate had the most significant impact on the yield of fatty methyl ester; a quadratic polynomial equation was obtained for methyl ester yield by multiple regression analysis. The predicted biodiesel yield was 0.928 (w/w) under the optimal conditions and the subsequent verification experiments with biodiesel yield of 0.936 ± 0.014 (w/w) confirmed the validity of the predicted model. CONCLUSION: RSM and CCD were suitable techniques to optimize the transesterification of soybean oil for biodiesel production by soluble lipase NS81006. The related lipase NS81006 reuse stability, chemical or genetic modification, and transesterification mechanism should be taken into consideration. Copyright © 2007 Society of Chemical Industry [source] Optimization of growth medium for the production of ,-amylase from Bacillus amyloliquefaciens using response surface methodologyJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 4 2006M Saban Tanyildizi Abstract The optimization of nutrient levels for the production of ,-amylase by Bacillus amyloliquefaciens was carried out using response surface methodology (RSM) based on the 23 factorial central composite design (CCD). This procedure limited the number of actual experiments performed while allowing for possible interactions between three components. RSM was adopted to derive a statistical model for the effect of starch, peptone and yeast extract (YE) on ,-amylase production. The P -value of the coefficient for linear effects of starch and YE concentration was <0.0001, suggesting that this was the principal experimental variable, having the greatest effect on the production of ,-amylase. The optimal combinations of media constituents for maximum ,-amylase production were determined as 12.61 g L,1 starch, 2.83 g L,1 peptone and 1.25 g L,1 YE. The optimization of the medium resulted not only in a 34% higher enzyme activity than unoptimized medium but also in a reduced amount of the required medium constituents. Copyright © 2006 Society of Chemical Industry [source] Modeling Randomness in Judging Rating Scales with a Random-Effects Rating Scale ModelJOURNAL OF EDUCATIONAL MEASUREMENT, Issue 4 2006Wen-Chung Wang This study presents the random-effects rating scale model (RE-RSM) which takes into account randomness in the thresholds over persons by treating them as random-effects and adding a random variable for each threshold in the rating scale model (RSM) (Andrich, 1978). The RE-RSM turns out to be a special case of the multidimensional random coefficients multinomial logit model (MRCMLM) (Adams, Wilson, & Wang, 1997) so that the estimation procedures for the MRCMLM can be directly applied. The results of the simulation indicated that when the data were generated from the RSM, using the RSM and the RE-RSM to fit the data made little difference: both resulting in accurate parameter recovery. When the data were generated from the RE-RSM, using the RE-RSM to fit the data resulted in unbiased estimates, whereas using the RSM resulted in biased estimates, large fit statistics for the thresholds, and inflated test reliability. An empirical example of 10 items with four-point rating scales was illustrated in which four models were compared: the RSM, the RE-RSM, the partial credit model (Masters, 1982), and the constrained random-effects partial credit model. In this real data set, the need for a random-effects formulation becomes clear. [source] RESPONSE SURFACE METHODOLOGY FOR STUDYING THE QUALITY CHARACTERISTICS OF COWPEA (VIGNA UNGUICULATA)-BASED TEMPEHJOURNAL OF FOOD PROCESS ENGINEERING, Issue 4 2010GEORGE AMPONSAH ANNOR ABSTRACT Response surface methodology was used to optimize the processing conditions in the preparation of cowpea tempeh. The independent factors studied were boiling time (varying from 5 to 30 min), incubation time (varying from 12 to 48 h) and incubation temperatures (varying from 25 to 50C), whereas the dependent factors were protein content, protein solubility, pH, titratable acidity and total color difference (using L, a* and b*). Regression models were generated and adequacy was tested with regression coefficients (R2) and the lack-of-fit tests. Optimum processing conditions were determined by method of superimposition. There was a strong and significant influence (P < 0.01) of the quadratic effect of the incubation time on the protein content of the cowpea tempeh, with similar significance (P < 0.01) noted in protein solubility with increasing boiling time. The optimum processing conditions observed for the preparation of cowpea tempeh were boiling time of about 20 min, incubation time of about 28 h and incubation temperature of about 37C. PRACTICAL APPLICATIONS Response surface methodology (RSM), as a statistical tool, has been effectively used in food process applications. This study embraced the use of RSM in the optimization of the processing conditions involved in the preparation of cowpea tempeh. Superimposition of the contour plots developed from the regression models indicated that cowpea with optimum quality characteristics should be processed at a boiling time of 20 min, incubation time of 28 h and incubation temperature of 37C. These conditions could be adopted for the industrial production of cowpea tempeh. [source] OPTIMIZATION OF PERMEABILIZATION PROCESS FOR LACTOSE HYDROLYSIS IN WHEY USING RESPONSE SURFACE METHODOLOGYJOURNAL OF FOOD PROCESS ENGINEERING, Issue 3 2009GURPREET KAUR ABSTRACT To overcome the permeability barrier and prepare whole cell biocatalysts with high activities, permeabilization of Kluyveromyces marxianus var. lactis NCIM 3566 in relation to, -galactosidase activity was optimized using cetyltrimethylammonium bromide (CTAB) as permeabilizing agent. Permeabilized whole cells can be advantageous over pure enzyme preparations in terms of cost-effectiveness and increased stability maintained by the intracellular environment. Response surface methodology (RSM) was applied to optimize concentration of CTAB, temperature and the treatment time for maximum permeabilization of yeast cells. The optimum operating conditions for permeabilization process to achieve maximum enzyme activity obtained by RSM were 0.06% (w/v) CTAB concentration, 28C temperature and process duration of 14 min. At these conditions of process variables, the maximum value of enzyme activity was found to be 1,334 IU/g. The permeabilized yeast cells were highly effective and resulted in 90.5% lactose hydrolysis in whey. PRACTICAL APPLICATION , -Galactosidase is one of the most promising enzymes, which has several applications in the food, fermentation and dairy industry. However, the industrial applications of , -galactosidase have been hampered by the costs involved in downstream processing. The present investigation was focused on developing the low-cost technology for lactose hydrolysis based on permeabilization process. Disposal of lactose in whey and whey permeates is one of the most significant problems with regard to economics and environmental impact faced by the dairy industries. Keeping this in view, lactose hydrolysis in whey has been successfully performed using permeabilized Kluyveromyces marxianus cells. Hydrolysis of lactose using , -galactosidase converts whey into a potentially very useful food ingredient, which has immense applications in food industries. Its use has increased significantly in recent years, mainly in the dairy products and in digestive preparations. Lactose hydrolysis causes several potential changes in the manufacture and marketing of dairy products, including increased solubility, sweetness and broader fermentation possibilities. [source] SUPERCRITICAL CO2/ETHANOL EXTRACTION OF ASTAXANTHIN FROM BLUE CRAB (CALLINECTES SAPIDUS) SHELL WASTEJOURNAL OF FOOD PROCESS ENGINEERING, Issue 2 2001LETICIA FÉLIX-VALENZUELA ABSTRACT Astaxanthin (AX) is the major naturally occurring carotenoid pigment in marine crustaceans and the flesh of salmonids. These organisms are unable to synthesize AX de novo and when farmed commercially, require it in their feed. The high cost of synthetic AX has promoted research into new natural sources of ihe pigment, such as crustacean wastes. In this work, AX from demineralized crab (Callinectes sapidusj shell waste was extracted with a mixture of supercritical C2 and ethanol as a cosolvent. The effect of total solids load, pressure and temperature was assessed by response surface methodology (RSM). Extracted AX was determined by HPLC. The experimental data were fined to a second order model whereby the conditions for maximum extraction yield were defined (, 34 MPa, 45C and solids load of 25 g). Pressure and solids load were the most important factors affecting AX extraction yields. [source] OPTIMIZATION OF VACUUM PULSE OSMOTIC DEHYDRATION OF CANTALOUPE USING RESPONSE SURFACE METHODOLOGYJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 1 2005WILMER J. FERMIN ABSTRACT The optimum levels of vacuum pressure, concentration of osmotic solution and dehydration time for vacuum pulse osmotic dehydration of cantaloupe were determined by response surface methodology (RSM). The response surface equations ( P < 0.05 and lack of fit > 0.1) explain the 97.6, 88.0 and 97.1% of the variability in weight loss, water loss and °Brix increase, respectively, at 95% confidence level. The canonical analysis for each response indicated that the stationary point is a saddle point for weight loss and °Brix increase, and a point of maximum response for water loss. The region that best satisfied all the constraints (low values in weight loss and °Brix increase, and high value in water loss) is located within the intervals from 49.5 °Brix to 52.5 °Brix for concentration and from 75 min to 84 min for dehydration time at a vacuum pulse of 740 mbar. [source] Optimization Process of Black Soybean Natto Using Response Surface MethodologyJOURNAL OF FOOD SCIENCE, Issue 6 2009Ming-Chih Shih ABSTRACT:, Response surface methodology (RSM) was used to determine the optimum combinations of 3 factors, cooking time (40 to 120 min), inoculated bacteria populations (101 to 109 cells/100 g), and fermentation time (12 to 36 h) for producing black soybean natto. All of the responses (hardness, viscosity, and trichloacetic acid-soluble nitrogen) were significantly affected by the 3 factors. Fermentation time was the most important factor affecting quality of black soybean natto. Optimum combinations were cooking time 110 min, inoculated bacteria populations 102 to 104 cells/100 g, and fermentation time 30 to 33 h. [source] Fermentation of Reconstituted Skim Milk Supplemented with Soy Protein Isolate by Probiotic OrganismsJOURNAL OF FOOD SCIENCE, Issue 2 2008T.T. Pham ABSTRACT:, Utilization of lactose and production of organic acid were determined in reconstituted skim milk (RSM) and RSM supplemented with soy protein isolate (SPI) (RSMS) by 6 probiotic organisms, including L. acidophilus 4461, L. acidophilus 4962, L. casei 290, L. casei 2607, B. animalis subsp. lactis bb12, and B. longum 20099. The viable counts of probiotic organisms of RSM and RSMS were enumerated and pH measured during fermentation. Our results showed that 3% to 10% more lactose was utilized by all the 6 probiotic microorganisms from RSMS than RSM. All 6 probiotic organisms produced significantly more acetic acid in RSMS than RSM. However, the viable microbial populations in RSMS were lower than those in RSM due to lower pH of the former. It appears that addition of SPI enhanced lactose utilization and acetic acid production but slightly reduced the lactic acid production and the growth of probiotic microorganisms. [source] Antifungal Activity Stability of Flaxseed Protein Extract Using Response Surface MethodologyJOURNAL OF FOOD SCIENCE, Issue 1 2008Y. Xu ABSTRACT:, The stability of the antifungal activity of flaxseed (Linum usitatissimum) protein extract was evaluated in this study. Response surface methodology (RSM) using Box,Behnken factorial design was used to evaluate the effects of treatment variables, that is, temperature (50 to 90 °C), time (1 to 29 min), and pH (2 to 8), on the residual antifungal activity (RAA) against Penicillium chrysogenum, Fusarium graminearum, Aspergillus flavus, and a Penicillium sp. isolated from moldy noodles. Regression analyses suggested that the linear terms of the temperature and time had significant (P < 0.05) negative effects on the RAA against all test fungi, whereas that of pH had a significant (P < 0.1) positive role on the RAA of all 3 fungi. In addition, the RAA was significantly (P < 0.05) affected by the quadratic terms of time for all fungi, and the quadratic term of temperature played a significant (P < 0.1) role on RAA against F. graminearum. One interaction term (temperature-pH) was found to significantly (P < 0.1) affect the RAA against both Penicillium strains tested. The results indicated that , 90% antifungal activity was lost after the protein extracts were heated at 90 °C for 8 min except for F. graminearum. At pasteurization condition, , 50% activity was retained except for P. chrysogenum. The results also suggested that neutral and alkaline pH favored the antifungal activity stability of the protein extracts. Thus, flaxseed protein might be promising if used as a preservative in foods with neutral or alkaline pH requiring mild heat treatments. [source] Physicochemical Properties of Cellulose Selectively Oxidized with the 2,2,6,6-Tetramethyl-1-Piperidinyl Oxoammonium IonJOURNAL OF FOOD SCIENCE, Issue 5 2007D.S. Suh ABSTRACT:, This study examined the characteristics of the oxidation reaction on the primary alcohol groups in cellulose involving the 2,2,6,6-tetramethyl-1-piperidinyl oxoammonium ion (TEMPO) and determined the optimum conditions for the preparation of oxidized cellulose (OC). The applicability of OC in polysaccharide systems was also investigated. The effects of TEMPO, sodium bromide (NaBr), and temperature on the oxidation reaction time, yield, and selectivity for primary alcohol groups were examined using response surface methodology (RSM). The reaction time decreased with increases in the temperature and the levels of TEMPO and NaBr. The yield increased with the level of NaBr and decreased as the temperature increased. Selectivity increased with the temperature and decreased as the levels of TEMPO and NaBr increased. The optimum levels of TEMPO and NaBr and the optimum temperature for the production of OC were determined as 0.3 mM/100 mM anhydroglucose unit (AGU), 50 mM/100 mM AGU, and 25 °C, respectively. The water and oil binding capacity and viscosity of cellulose increased with oxidation. Wheat starch containing OC exhibited a decreased initial pasting temperature and setback, but increased peak viscosity, gelatinization, and retrogradation enthalpy (,H). The hardness of the wheat starch gel decreased significantly upon the addition of OC. [source] Response Surface Model for the Estimation of Escherichia coli O 157:H7 Growth under Different Experimental ConditionsJOURNAL OF FOOD SCIENCE, Issue 1 2005Rose Maria García-Gimeno ABSTRACT: In this study, a Response Surface Model (RSM) of Escherichia coli O157:H7 as affected by pH levels, sodium chloride and nitrite concentrations, temperature, and aerobic/anaerobic conditions is presented. The standard error of prediction (%SEP) obtained was acceptable for the growth rate prediction (33%SEP), although a bit high for lag time (53.01 %SEP). Mathematical validation demonstrated that the RSM predicts growth rate values on the fail-safe side in aerobic conditions and within the acceptable range (bias factor [Bf] = 0.99) with acceptable accuracy (accuracy factor [Af] = 1.15), as well as for lag time (Bf = 1.05; Af = 1.25). Temperature was found to have the greatest effect on the kinetic parameters, followed by NaCl concentration and pH. In the experimental range considered here (0 to 200 ppm), NaNO2 concentration was found to have a significant effect on growth rate but not on lag time. [source] Sequential Quadratic Programming for Development of a New Probiotic Dairy Tofu with Glucono-,-LactoneJOURNAL OF FOOD SCIENCE, Issue 7 2004M.-J. Chen ABSTRACT: The purpose of this research was to evaluate the effects of various concentrations of glucono-,-lactone (GDL) and skim milk powder, as well as the addition of prebiotics, on the rheology and probiotic viabilities of dairy tofu. Additionally, modern optimization techniques were applied to attempt to determine the optimal processing conditions and growth rate for the selected probiotics (Lactobacillus. acidophilus, L. casei, Bifidobacteria bifidum, and B. longum). There were 2 stages in this research to accomplish the goal. The 1st stage was to derive surface models using response surface methodology (RSM); the 2nd stage performed optimization on the models using sequential quadratic programming (SQP) techniques. The results were demonstrated to be effective. The most favorable production conditions of dairy tofu were 1% GDL, 0% peptides, 3% isomaltooligosaccharides (IMO), and 18% milk, as confirmed by subsequent verification experiments. Analysis of the sensory evaluation results revealed no significant difference between the probiotic dairy tofu and the GDL analog in terms of texture and appearance (P < 0.05). The viable numbers of probiotics were well above the recommended limit of 106 CFU/g for the probiotic dairy tofu throughout the tested storage period. [source] | ||||||||||||||||||||||||||||||||||||||||