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Central Composite Rotatable Design (central + composite_rotatable_design)
Selected AbstractsMultiple stressor effects of methoprene, permethrin, and salinity on limb regeneration and molting in the mud fiddler crab (UCA pugnax)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2009Todd A. Stueckle Abstract Exposure to multiple stressors from natural and anthropogenic sources poses risk to sensitive crustacean growth and developmental processes. Applications of synthetic pyrethroids and insect growth regulators near shallow coastal waters may result in harmful mixture effects depending on the salinity regime. The potential for nonadditive effects of a permethrin (0.01,2 ,g/L), methoprene (0.03,10 ,g/L), and salinity (10,40 ppt) exposure on male and female Uca pugnax limb regeneration and molting processes was evaluated by employing a central composite rotatable design with multifactorial regression. Crabs underwent single-limb autotomy followed by a molting challenge under 1 of 16 different mixture treatments. During the exposure (21,66 d), individual limb growth, major molt stage duration, abnormal limb regeneration, and respiration were monitored. At 6 d postmolt, changes in body mass, carapace width, and body condition factor were evaluated. Dorsal carapace tissue was collected, and protein and chitin were extracted to determine the composition of newly synthesized exoskeleton. The present results suggest chronic, low-dose exposures to multiple pesticide stressors cause less-than-additive effects on U. pugnax growth processes. Under increasing concentrations of methoprene and permethrin, males had more protein in their exoskeletons and less gain in body mass, carapace width, and body condition compared to females. Females exhibited less gain in carapace width than controls in response to methoprene and permethrin. Females also displayed elevated respiration rates at all stages of molt, suggesting a high metabolic rate. Divergent growth and fitness between the sexes over the long term could influence crustacean population resilience. [source] Comparative effects of pH and Vision® herbicide on two life stages of four anuran amphibian species,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2004Andrea N. Edginton Abstract Vision®, a glyphosate-based herbicide containing a 15% (weight:weight) polyethoxylated tallow amine surfactant blend, and the concurrent factor of pH were tested to determine their interactive effects on early life-stage anurans. Ninety-six-hour laboratory static renewal studies, using the embryonic and larval life stages (Gosner 25) of Rana clamitans, R. pipiens, Bufo americanus, and Xenopus laevis, were performed under a central composite rotatable design. Mortality and the prevalence of malformations were modeled using generalized linear models with a profile deviance approach for obtaining confidence intervals. There was a significant (p < 0.05) interaction of pH with Vision concentration in all eight models, such that the toxicity of Vision was amplified by elevated pH. The surfactant is the major toxic component of Vision and is hypothesized, in this study, to be the source of the pH interaction. Larvae of B. americanus and R. clamitans were 1.5 to 3.8 times more sensitive than their corresponding embryos, whereas X. laevis and R. pipiens larvae were 6.8 to 8.9 times more sensitive. At pH values above 7.5, the Vision concentrations expected to kill 50% of the test larvae in 96-h (96-h lethal concentration [LC50]) were predicted to be below the expected environmental concentration (EEC) as calculated by Canadian regulatory authorities. The EEC value represents a worst-case scenario for aerial Vision application and is calculated assuming an application of the maximum label rate (2.1 kg acid equivalents [a.e.]/ha) into a pond 15 cm in depth. The EEC of 1.4 mg a.e./L (4.5 mg/L Vision) was not exceeded by 96-h LC50 values for the embryo test. The larvae of the four species were comparable in sensitivity. Field studies should be completed using the more sensitive larval life stage to test for Vision toxicity at actual environmental concentrations. [source] Optimisation study of gum extraction from Basil seeds (Ocimum basilicum L.)INTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 9 2009Seyed M. A. Razavi Summary Basil seed (Ocimum basilicum L.) is cultivated in large quantities in different regions of Iran. This seed has reasonable amounts of gum with good functional properties which is comparable with commercial food hydrocolloids. A central composite rotatable design was applied to evaluate the effects of temperature, pH and water/seed ratio on the yield, apparent viscosity and protein content of water-extracted Basil seed gum. All of the variables significantly (P < 0.05) affected the extraction yield, whereas the effect of water/seed ratio on apparent viscosity and the effects of pH and water/seed ratio on protein content were not significant (P > 0.05). Numerical optimisation determined the optimum extraction conditions based on the highest yield and viscosity and the lowest protein content as being temperature 68.71 °C, pH 8.09 and water/seed ratio 65.98:1. Power law model well described non-Newtonian pseudoplastic behaviour of BSG. Flow behaviour index (n) and consistency index (K) of 1% crude and pure BSG samples were 0.306, 0.283 and 17.46, 20.22 Pa sn, respectively. [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] The effect of addition of calcium and processing temperature on the quality of guava in syrupINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 4 2006Ana Carla K. Sato Summary The effect of process temperature and calcium concentration in the cooking syrup of guava in syrup were studied. A central composite rotatable design (CCRD) was used to optimize the quality indices of the final product, such as texture and colour. All of the processed guava quality parameters were compared with those of the fresh fruit and of a commercial sample to evaluate the effects of processing on the final product quality. Increase in the process temperature promoted changes in the final product colour, the fruit becoming darker. On the contrary, higher calcium concentrations in the cooking syrup produced lighter samples, with colour parameters closer to those of the fresh fruit. In general, the addition of calcium promoted better texture and minimized the negative effects of temperature on the mechanical properties. Processed guavas had higher rupture stress and strain than fresh fruit, indicating an increase in hardness and elasticity. [source] PURIFICATION AND CHARACTERIZATION OF BACTERIOCIN FROM WEISSELLA PARAMESENTEROIDES DFR-8, AN ISOLATE FROM CUCUMBER (CUCUMIS SATIVUS)JOURNAL OF FOOD BIOCHEMISTRY, Issue 5 2010AJAY PAL ABSTRACT Bacteriocin from Weissella paramesenteroides DFR-8 isolated from cucumber (Cucumis sativus) was purified by using only two steps, viz., pH-mediated cell adsorption,desorption method and gel permeation chromatography. A single peak observed in the purity check by analytical Reverse Phase-High Performance Liquid Chromatography (Waters 600 analytical HPLC system, Milford, MA) and a single band (molecular weight,3.74 kDa) shown on SDS-PAGE analysis strongly indicated the homogeneity of the bacteriocin preparation. Treatment with proteolytic enzymes abolished the antimicrobial activity indicating the proteinaceous nature of bacteriocin. The purified bacteriocin exhibited a broad inhibitory spectrum against foodborne pathogens and spoilage microorganisms, including gram-negative bacteria such as Salmonella typhimurium, Vibrio parahaemolyticus, Aeromonas hydrophila and Listeria monocytogenes. Response surface methodology was employed to study the interactive effect of temperature and pH on bacteriocin activity, and a regression equation was developed. The bacteriocin retained full activity after storage at,20C for 90 days, while partial and complete activity loss was observed when stored at 4 and 37C, respectively. PRACTICAL APPLICATION In recent years, bacteriocins of lactic acid bacteria have gained much attention as food biopreservatives because of their origin from generally regarded as safe organisms. In spite of various bacteriocins studied worldwide, studies on bacteriocins of Weissella paramesenteroides remain rare. The present work involves the purification of bacteriocin up to absolute homogeneity from W. paramesenteroides, an isolate first time reported from cucumber (Cucumis sativus). The purified bacteriocin (molecular weight ,3.74 kDa) was found to inhibit a large number of foodborne pathogens, including Listeria monocytogenes, which is resistant to commercially available bacteriocin, i.e., nisin. The application of central composite rotatable design enabled us to design a regression equation from which the residual activity of bacteriocin can be predicted at any given conditions of temperature and pH within the experimental domain. The broad inhibitory spectrum and thermostability of bacteriocin suggest its potential application in food preservation. [source] Optimisation of kojic acid monolaurate synthesis with lipase PS from Pseudomonas cepaciaJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 6 2002Chee-Shan Chen Abstract To improve the instability of kojic acid in food and cosmetic use, the esterification of kojic acid catalysed by lipase from Pseudomonas cepacia (Amano PS) to synthesise kojic acid monolaurate (KAML) was investigated in this study. Response surface methodology (RSM) with a five-level/five-factor central composite rotatable design (CCRD) was employed to evaluate the effects of synthesis parameters such as reaction time (8,24,h), temperature (35 55,°C), enzyme amount (10,50%), substrate molar ratio of lauric acid to kojic acid (1:1,3:1) and added water content (0,20%) on the percentage molar conversion to KAML by direct esterification. Reaction time and added water content were the most important variables, while substrate molar ratio had less effect on percentage molar conversion. Based on canonical analysis and ridge maximum analysis, optimal synthesis conditions were reaction time 19,h, temperature 44,°C, enzyme amount 38%, substrate molar ratio 2:1 and added water content 10%. The predicted value was 85% and the actual experimental value 82% molar conversion. © 2002 Society of Chemical Industry [source] | ||||||||||