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Degradation Kinetics (degradation + kinetics)
Kinds of Degradation Kinetics Selected AbstractsTHERMAL DEGRADATION KINETICS OF SUCROSE, GLUCOSE AND FRUCTOSE IN SUGARCANE MUST FOR BIOETHANOL PRODUCTIONJOURNAL OF FOOD PROCESS ENGINEERING, Issue 5 2006J. NOLASCO JR. ABSTRACT Thermal degradation of sugars contained in sugarcane must (21.5°Brix, pH 6.14) was evaluated at temperatures of 110, 120, 130 and 140C, using the thermal-death-time tube method, determining remaining sugars by high-pressure liquid chromatography. The study analyzed thermal degradation kinetics of both the total reducing sugars (TRS) and glucose and fructose individually. All curves of remaining sugars presented strong nonlinearity, with initial shoulder and final tail adjusted by an extended logistic model that was adapted for two species for TRS, and a simple logistic model for the monosaccharides. It was shown that rate constants are influenced by temperature according to two irreconcilable methods: the Arrhenius and the Bigelow methods. Obtained activation energies for fructose and glucose were quite coincident, 140.37 and 140.23 kJ/mol, respectively. Thermal resistance parameters were 21.59 and 21.61C, respectively. Comparison of the rate constants revealed that fructose degraded approximately 9,10 times faster than glucose. [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] Effects of High-Pressure Pretreatment and Calcium Soaking on the Texture Degradation Kinetics of Carrots during Thermal ProcessingJOURNAL OF FOOD SCIENCE, Issue 5 2004D.N. Sila ABSTRACT: Carrots (Daucus carota) pretreated under different high-pressure conditions were thermally processed at temperatures in the range of 90°C to 110°C. Texture degradation (hardness) was monitored objectively using a texture analyzer. For a given thermal treatment, the rate constant (k-value) decreased with increasing pretreatment pressure. A high-pressure pretreatment (200 to 500 MPa) at 60°C for 15 min resulted in a more pronounced texture improvement compared with the same pretreatment at 20°C and 40°C, respectively. Calcium impregnation conferred more beneficial effects when applied immediately after the high-pressure pretreat-ment. The observed changes in texture characteristics were associated with the degree of methylation of carrot pectins, which is dependent on pectinmethylesterase (PME) activity. [source] Degradation Kinetics of Capsanthin in Paprika (Capsicum annuum L.) as Affected by HeatingJOURNAL OF FOOD SCIENCE, Issue 1 2001J.H. Shin ABSTRACT: Diluted juice of paprika was heated at 80, 90 and 100°C with holding times of 0, 2, 4, 8 and 16 min. Capsanthin in each sample was determined by HPLC. The degradation kinetics of capsanthin was studied by two groups of reaction models including elementary reaction rate models and those of modified square root-based pseudo (MRBP-). The MRBP-1st order reaction rate model was proven as an appropriate model in this study. The pseudo Q10 (PQ10) value was 1.045 and the predicted half-life (capsanthin 2,850 mg/L) was 27.47, 21.23 and 15.23 min, respectively, at 80, 90 and 100°C. [source] Thermal Degradation Kinetics of Nylon 66: Experimental Study and Comparison with Model PredictionsMACROMOLECULAR REACTION ENGINEERING, Issue 5 2007Mark A. Schaffer Abstract An experimental investigation of nonoxidative thermal degradation kinetics of nylon 66 melt under high temperature (280,300,°C) and low water content (0.02,0.14 wt.-%) conditions is presented. Experimental data for the time evolution of polymer end-group concentrations and degradation-product generation rates were compared with the predictions of the only published kinetic model. The omitted influence of water content is a plausible partial explanation for the considerable discrepancy between model predictions and some data. Several previously unreported or unquantified degradation products were identified and measured. Potential additional reactions to account for these results in future kinetic models are proposed. [source] Degradation kinetics of ptaquiloside in soil and soil solutionENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2008Rikke Gleerup Ovesen Abstract Ptaquiloside (PTA) is a carcinogenic norsesquiterpene glycoside produced in bracken (Pteridium aquilinum (L.) Kuhn), a widespread, aggressive weed. Transfer of PTA to soil and soil solution eventually may contaminate groundwater and surface water. Degradation rates of PTA were quantified in soil and soil solutions in sandy and clayey soils subjected to high natural PTA loads from bracken stands. Degradation kinetics in moist soil could be fitted with the sum of a fast and a slow first-order reaction; the fast reaction contributed 20 to 50% of the total degradation of PTA. The fast reaction was similar in all horizons, with the rate constant k1F ranging between 0.23 and 1.5/h. The slow degradation, with the rate constant k1S ranging between 0.00067 and 0.029/h, was more than twice as fast in topsoils compared to subsoils, which is attributable to higher microbial activity in topsoils. Experiments with sterile controls confirmed that nonmicrobial degradation processes constituted more than 90% of the fast degradation and 50% of the slow degradation. The lower nonmicrobial degradation rate observed in the clayey compared with the sandy soil is attributed to a stabilizing effect of PTA by clay silicates. Ptaquiloside appeared to be stable in all soil solutions, in which no degradation was observed within a period of 28 d, in strong contrast to previous studies of hydrolysis rates in artificial aqueous electrolytes. The present study predicts that the risk of PTA leaching is controlled mainly by the residence time of pore water in soil, soil microbial activity, and content of organic matter and clay silicates. [source] Degradation kinetics of meta- and para-aromatic polyamidesADVANCES IN POLYMER TECHNOLOGY, Issue 1 2003Arturo Horta Abstract Poly(m -phenylenediamineisophthal)amide (MPD-I) and poly(p -phenylenediamineterephthal)amide (PPD-T) are among the most important high-tech polymers. The degradation of three MPD-I fibers with different molecular weight distributions and a PPD-T fiber was studied in a proprietary laboratory degradation chamber. The results were fitted satisfactorily to a kinetic model describing the degradation as a combination of thermal scission, oxidation, and hydrolysis. PPD-T degradation is slower than that of MPD-I, and MPD-I resistance to degradation increases as polydispersity decreases. © 2003 Wiley Periodicals, Inc. Adv Polym Techn 22: 15,21, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.10031 [source] Microenvironmental pH modulation in solid dosage formsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 5 2007Sherif I. Farag Badawy Abstract There are many reports in the literature referring to the effect of ,microenvironmental pH' on solid dosage form performance, particularly stability and dissolution profiles. Several techniques have been proposed for the measurement of the microenvironmental pH. Those techniques use certain assumptions and approximations and many of them employ a solution calibration curve of a probe to predict hydrogen ion activity in a substantially dry solid. Despite the limitation of the methodology, it is clear from the literature that microenvironmental pH has a significant impact on stability of compounds which demonstrate pH dependent stability in solution. Degradation kinetics of such compounds, and in some cases degradation profile as well, are dependent on the microenvironmental pH of the solid. Modulation of the microenvironmental pH through the use of pH modifiers can hence prove to be a very effective tool in maximizing solid dosage form stability. Judicial selection of the appropriate pH modifier, its concentration and the manufacturing process used to incorporate the pH modifier is necessary to enhance stability. Control of microenvironmental pH to maximize stability can be achieved without the use of pH modifier in some cases if an appropriate counter ion is used to provide an inherently optimal pH for the salt. Microenvironmental pH modulation was also shown to control the dissolution profile of both immediate and controlled release dosage forms of compounds with pH dependent solubility. The pH modifiers have been used in conjunction with high energy or salt forms in immediate release formulations to minimize the precipitation of the less soluble free form during initial dissolution. Additionally, pH modifiers were utilized in controlled release dosage forms of weakly basic drugs which exhibit diminished release in dissolution media with high pH. The incorporation of acidic pH modifiers in the controlled release formulation increases the solubility of the basic drug even as the high pH dissolution medium enters into the dosage form hence increasing drug release rate. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96: 948,959, 2007 [source] Degradation kinetics of beetroot pigment encapsulated in polymeric matricesJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 8 2001George S Serris Abstract Kinetic studies on the degradation of water-soluble beetroot pigment, mainly consisting of the betalain betanin, encapsulated in three different matrices (pullulan and two maltodextrin samples differing in their molecular weight) were carried out under various water activity (aw,=,0.23, 0.43, 0.64, 0.75 and 0.84) and temperature (30, 40 and 50,°C) conditions. The water sorption behaviour of these materials was also examined. Degradation of the pigment was monitored by absorbance measurements at 537,nm (,max of betanin). The highest values of the rate constants for degradation were observed at an intermediate water activity level (aw,=,0.64) for all matrices and all three storage temperatures examined. An attempt to relate the degradation kinetics to the molecular mobility of the wall material was not successful. Pigment losses were observed even at temperatures below the glass transition temperature (Tg) of the polymeric matrices, although degradation was largely slowed down in the glassy state. In the vicinity of the Tg zone, where all polymers go through a glass , rubber transition, there was not a distinct change in the reaction rate, which could reflect the pronounced changes in molecular mobility of the wall material. In fact, some of the lower degradation rates were observed mostly under conditions where the matrices were fully plasticised (ie rubbery) and ,collapsed', implying that the degradation kinetics is not governed by factors related only to the physical state of the polymeric wall material. © 2001 Society of Chemical Industry [source] Reaction kinetics for the degradation of phenol and chlorinated phenols using Fenton's reagentENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 1 2006Asim K. De Abstract Fenton's reaction is an advanced treatment technology often used for the removal of hazardous and refractory organic compounds from industrial wastewaters. It can effectively be used to degrade phenol and chlorophenols. The initial contaminant concentrations as well as the concentration of hydrogen peroxide and ferrous ions in aqueous solution have a significant effect on the effective degradation of contaminants. For a particular concentration of initial substrate in solution there should be an optimum level of ferrous ion concentration in the reaction medium. Based on experimental observations, a probable mechanism for Fenton's degradation kinetics has been proposed and a rate equation developed. From the rate expression, OH· radical reaction rate constants for the degradation of three compounds,phenol and o- and p-chlorophenols,in Fenton reaction were calculated to have values of 2.53 × 107, 2.38 × 107, and 2.45 × 107 m3 mol,1 s,1, respectively. © 2005 American Institute of Chemical Engineers Environ Prog, 2005 [source] Effect of mass-transfer limitations on bioavailability of sorbed naphthalene in synthetic model soil matricesENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2000Hendricus Mulder Abstract External and internal mass-transfer resistances influencing the bioavailability of sorbed naphthalene in a synthetic model matrix for soil aggregates were investigated in batch experiments in mixed reactors. Amberlite® adsorption resins (XAD4 and XAD7) were used as the synthetic model for soil aggregates. The effect of hydrodynamic conditions in the slurry phase on the diffusive transport across a stagnant film surrounding the model particles was studied. In addition, a mechanistic model was developed based on mass balances, diffusion equations, a nonlinear sorption isotherm, and microbial degradation kinetics. Experimental results could be explained well with this model. In the absence of external transfer limitations, intraparticle effective diffusion coefficients of (3.55 ± 0.10) × 10,9 m2/s and (5.29 ± 0.86) × 10,10 m2/s were determined for naphthalene in Amberlite XAD4 and XAD7, respectively. [source] Antioxidant Activity of Degradable Polymer Poly(trolox ester) to Suppress Oxidative Stress Injury in the CellsADVANCED FUNCTIONAL MATERIALS, Issue 1 2010Paritosh P. Wattamwar Abstract Oxidative stress is a pathological condition that has been implicated as a central player in a variety of diseases, including vascular and neurodegenerative diseases. More recently, oxidative stress has also been shown to be involved in the biological incompatibility of many materials, especially at the nanoscale. As such, there is a critical need for new biomaterials that can inhibit this response, improving the compatibility of medical devices. In this work, trolox, a synthetic antioxidant and water-soluble analogue of Vitamin E, is polymerized to form an oxidation active polymer as a new class of biomaterial. Synthesized poly(trolox ester) polymers were formulated into nanoparticles using a single emulsion technique, and their size was controlled by changing the polymer concentration in the organic solvent. Nanoparticle cytotoxicity, protective effects against cellular oxidative stress, and degradation kinetics were all evaluated. Poly(trolox ester) nanoparticles were found to have little to no cytotoxicity and were capable of suppressing cellular oxidative stress induced by cobalt nanoparticles. In vitro degradation studies of poly(trolox ester) nanoparticles indicate that the antioxidant activity of nanoparticles was derived from its enzymatic degradation to release active antioxidants. [source] Biodegradable Dextran Nanogels for RNA Interference: Focusing on Endosomal Escape and Intracellular siRNA DeliveryADVANCED FUNCTIONAL MATERIALS, Issue 9 2009Koen Raemdonck Abstract The successful therapeutic application of small interfering RNA (siRNA) largely relies on the development of safe and effective delivery systems that are able to guide the siRNA therapeutics to the cytoplasm of the target cell. In this report, biodegradable cationic dextran nanogels are engineered by inverse emulsion photopolymerization and their potential as siRNA carriers is evaluated. The nanogels are able to entrap siRNA with a high loading capacity, based on electrostatic interaction. Confocal microscopy and flow cytometry analysis reveal that large amounts of siRNA-loaded nanogels can be internalized by HuH-7 human hepatoma cells without significant cytotoxicity. Following their cellular uptake, it is found that the nanogels are mainly trafficked towards the endolysosomes. The influence of two different strategies to enhance endosomal escape on the extent of gene silencing is investigated. It is found that both the application of photochemical internalization (PCI) and the use of an influenza-derived fusogenic peptide (diINF-7) can significantly improve the silencing efficiency of siRNA-loaded nanogels. Furthermore, it is shown that an efficient gene silencing requires the degradation of the nanogels. As the degradation kinetics of the nanogels can easily be tailored, these particles show potential for intracellular controlled release of short interfering RNA. [source] Biodegradation and transport of benzene, toluene, and xylenes in a simulated aquifer: comparison of modelled and experimental resultsHYDROLOGICAL PROCESSES, Issue 16 2002Jiin-Shuh Jean Abstract Both laboratory experiments and numerical modelling were conducted to study the biodegradation and transport of benzene,toluene,xylenes (BTX) in a simulated semi-confined aquifer. The factors incorporated into the numerical model include advection, hydrodynamic dispersion, adsorption, and biodegradation. The various physico-chemical parameters required by the numerical model were measured experimentally. In the experimental portion of the study, BTX compounds were introduced into the aquifer sand. After the contaminants had been transported through the system, BTX concentrations were measured at 12 equally spaced wells. Subsequently, microorganisms obtained from the activated sludge of a sewage treatment plant and cultured in BTX mixtures were introduced into the aquifer through the 12 sampling wells. The distribution data for BTX adsorption by the aquifer sand form a nonlinear isotherm. The degree of adsorption by the sand varies, depending on the composition of the solute. The degradation time, measured from the time since the bacteria were added to the aquifer until a specific contaminant was no longer detectable, was 35,42 h for BTX. The dissolved oxygen, after degradation by BTX compounds and bacteria, was consumed by about 40,60% in the entire simulated aquifer; thus the aerobic conditions were maintained. This study provides insights for the biodegradation and transport of BTX in aquifers by numerical modelling and laboratory experiments. Experimental and numerical comparisons indicate that the results by Monod degradation kinetics are more accurate than those by the first-order degradation kinetics. Copyright © 2002 John Wiley & Sons, Ltd. [source] Use of real-time FT-IR monitoring of a pharmaceutical compound under stress atmospheric conditions to characterize its solid-state degradation kineticsINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 1 2010Peter J. Skrdla The use of online FT-IR is described for investigating the degradation kinetics of the solid amorphous pharmaceutical compound, fosaprepitant dimeglumine (FD), under stress storage conditions (i.e., high temperature, T, and humidity, % RH). It is found that under conditions of elevated T and % RH, the kinetics are denucleation rate limited for the deliquescence of the amorphous FD solid, based on the high quality fits obtained to the authors' dispersive kinetic model for that mechanism. At elevated T and low % RH, it is found that a classical, first-order hydrolysis mechanism for the degradation of FD (which forms crystalline aprepitant, AP) significantly contributes to the overall conversion rate. That mechanism is similar to the one observed previously for the solution-phase hydrolysis of FD. Appropriate kinetic models are proposed for the FD-to-AP conversion under all of the experimental conditions investigated in this work. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 42: 25,36, 2010 [source] Original article: Thermal and light degradation kinetics of anthocyanin extracts from mangosteen peel (Garcinia mangostana L.)INTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 9 2010Renan C. Chisté Summary The stability and half-life time of anthocyanin extracts from mangosteen peel were studied under controlled oxygen supply, undergoing the influence of light source (fluorescent, incandescent, infrared and ultraviolet) and storage temperature (5, 28, 40 and 50 °C). The kinetic parameters for anthocyanin degradation, under different illumination conditions fit the first-order reaction model, and the exposition under fluorescent light resulted in a higher half-life time (597 h), followed by incandescent (306 h), ultraviolet (177 h) and infrared (100 h). The kinetic behaviour for the storage in different temperatures also fit the first order, and at 5 °C the highest half-life time (4006 h) was found, followed by 28 °C (370 h), 40 °C (125 h) and 50 °C (93 h). The activation energy was 14.7 Kcal.mol,1, and Q10 values showed that at 5 °C the anthocyanin extracts were more sensitive to storage temperature changes compared to the other tested temperatures. [source] Degradation of isooctane by Mycobacterium austroafricanum IFP 2173: growth and catabolic pathwayJOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2004F. Solano-Serena Abstract Aims:, Isooctane (2,2,4-trimethylpentane), a major component of gasoline formulations, is recalcitrant to biodegradation probably because of the quaternary carbon group it contains. Information on the biodegradability of this hydrocarbon is essential to evaluate its fate in the environment. For these reasons, the degradation kinetics and the catabolic pathway of isooctane were investigated in Mycobacterium austroafricanum IFP 2173, the only strain characterized to use it as sole carbon and energy source. Methods and Results:, The selected strain exhibited a rather moderate maximum growth rate (,max = 0·053 h,1) but degraded isooctane up to 99% with a mineralization yield of 45%, indicating attack of the quaternary carbon group. The GC/MS identification of metabolites, 2,4,4-trimethylpentanoic and dimethylpropanoic (pivalic) acids, which transiently accumulated in the cultures indicated that degradation started from the isopropyl extremity of the molecule and subsequently proceeded by catabolism of the tert -butyl moiety. The degradation of putative metabolic intermediates was investigated. The initial isooctane oxidation system was tentatively characterized. Conclusions:, The isooctane-degrading strain harboured two candidate systems for initial alkane oxidation. Although a cytochrome P450 was induced by isooctane degradation, the functional oxidation system was probably a nonheme alkane monooxygenase as indicated by PCR amplification and RT-PCR expression of an alkB gene. Significance and Impact of the Study:, Isooctane is a recalcitrant branched alkane. A plausible pathway of its degradation by Myco. austroafricanum was put forward. [source] Thermal degradation kinetics of epoxy/organically modified montmorillonite nanocompositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2008Ivan Brnardi Abstract Nanocomposites based on a commercial epoxy resin and organically modified montmorillonites (OMMTs), containing 5 and 10 phr OMMT, were prepared and characterized. Poly(oxypropylene) diamine (Jeffamine D400) and octadecylamine were used as organic modifiers. Another poly(oxypropylene) diamine (Jeffamine D230) was used as a curing agent. The thermal degradation kinetics of the neat resin system and nanocomposites were investigated by thermogravimetric analysis. The dispersion of silicate layers within the crosslinked epoxy matrix was verified by transmission electron microscopy. The activation energy of degradation for the investigated systems was determined by the isoconversional Kissinger,Akahira,Sunose method. The thermal behavior of the neat resin systems and nanocomposites was modeled with an empirical kinetic model. The influence of organic modifiers and the OMMT loading on the thermal stability of the nanocomposites was discussed. © 2007 Wiley Periodicals, Inc. JAppl Polym Sci, 2008 [source] Thermal oxidative degradation kinetics of PP and PP/mg (OH)2 flame-retardant compositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2007Xiaolang Chen Abstract The thermal stability and thermal oxidative degradation kinetics of polypropylene (PP) and flame-retardant PP composites filled with untreated and treated magnesium hydroxide (MH) in air were studied by thermogravimetric analysis (TGA). The effect of the heating rate in dynamic measurements (5°C,30°C/min) on kinetic parameters such as activation energy was also investigated. The Kissinger and Flynn,Wall,Ozawa methods were used to determine the apparent activation energy for the degradation of neat PP and flame-retardant PP composites. The results of TGA showed that the addition of untreated or treated MH improved the thermal oxidative stability of PP in air. The kinetic results showed that the apparent activation energy for degradation of flame-retardant PP composites was much higher than that of neat PP, suggesting that the flame retardant used in this work had a great effect on the mechanisms of pyrolysis and combustion of PP. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1978,1984, 2007 [source] THERMAL DEGRADATION KINETICS OF SUCROSE, GLUCOSE AND FRUCTOSE IN SUGARCANE MUST FOR BIOETHANOL PRODUCTIONJOURNAL OF FOOD PROCESS ENGINEERING, Issue 5 2006J. NOLASCO JR. ABSTRACT Thermal degradation of sugars contained in sugarcane must (21.5°Brix, pH 6.14) was evaluated at temperatures of 110, 120, 130 and 140C, using the thermal-death-time tube method, determining remaining sugars by high-pressure liquid chromatography. The study analyzed thermal degradation kinetics of both the total reducing sugars (TRS) and glucose and fructose individually. All curves of remaining sugars presented strong nonlinearity, with initial shoulder and final tail adjusted by an extended logistic model that was adapted for two species for TRS, and a simple logistic model for the monosaccharides. It was shown that rate constants are influenced by temperature according to two irreconcilable methods: the Arrhenius and the Bigelow methods. Obtained activation energies for fructose and glucose were quite coincident, 140.37 and 140.23 kJ/mol, respectively. Thermal resistance parameters were 21.59 and 21.61C, respectively. Comparison of the rate constants revealed that fructose degraded approximately 9,10 times faster than glucose. [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] Thermal and Storage Stability of Nutraceuticals in a Milk Beverage Dietary SupplementJOURNAL OF FOOD SCIENCE, Issue 3 2007M. Uzzan ABSTRACT:, Under the Dietary Supplement Health and Education Act (DSHEA), fluid skim milk can be used to serve as a vehicle to deliver certain metabolites (nutraceuticals or new dietary ingredients), which provide health benefits as related to aging problems for those over 55. This opens a new avenue for an increase in milk consumption and may replace taking pills. Milk beverages enriched with various nutraceutical ingredients (soy isoflavones, glucosamine, chondroitin sulfate, creatine, and lactoferrin) were thermally processed at different combinations of temperatures from 72 to 138 °C for different holding times using a Microthermics pilot plant thermal processing unit and were incubated at refrigeration, room, or elevated storage temperatures. Residual concentrations of the active compounds were measured by high performance liquid chromatography or by immunodifusion (for lactoferrin) and degradation kinetics were determined. Results showed a very good stability of isoflavones and chondroitin sulfate in the milk environment while glucosamine, lactoferrin, and creatin showed only limited stability at either processing or storage. Glucosamine destabilized the milk protein system at boiling temperature or higher, which caused drastic precipitation in the heat exchangers. Nevertheless, all the tested nutraceutical compounds can be used to design milk beverage dietary supplements but an overrun of over 25% may be required for some of them. [source] Microencapsulation by Spray Drying of Multiple Emulsions Containing CarotenoidsJOURNAL OF FOOD SCIENCE, Issue 7 2004M.E. Rodríduez-Huezo ABSTRACT: Water-in-oil-in-water (W1/O/W2) multiple emulsions with 25% and 35% solids contents were spray-dried producing microcapsules with 3.9:1, 2.6:1, and 1.4:1 biopolymers blend to primary emulsion ratios and 0.25% (w/w) theoretical carotenoids concentration. Microcapsules with better morphology, encapsulation efficiency, and larger particle size were those obtained from higher biopolymers blend to primary emulsion ratios and solids content, but showed relatively higher carotenoids degradation kinetics than microcapsules made with lower biopolymers blend to primary emulsion ratios and solids content, which exhibited poorer morphology, encapsulation efficiency, and smaller particle size. Microcapsules stored at different water activities showed maximum carotenoids degradation at a water activity (aw) of 0.628, with lower carotenoids degradation occurring at lower or higher aw. [source] COMPARISON OF MECHANICAL TESTS FOR EVALUATING TEXTURAL CHANGES IN POTATOES DURING THERMAL SOFTENINGJOURNAL OF TEXTURE STUDIES, Issue 6 2002W. K. SOLOMON ABSTRACT The changes in the texture of cylindrical samples of potato tissues immersed in water at 60, 70, 80 and 90C for up to 80 min were monitored at each temperature in terms of tangent modulus of elasticity in axial and radial compression tests, and elasticity and viscosity parameters in creep and stress relaxation tests. The magnitude of all mechanical test parameters decreased with an increase in heating time and temperature. The creep and stress relaxation responses of individual potato samples were adequately represented by respective mechanical models (R2= 0.94 to 0.99). The mechanical test parameters followed apparent first-order degradation kinetics due to the effect of thermal softening, and the rate constant was used as an index of the sensitivity of a mechanical test. The radial compression test was relatively more sensitive than the axial test. Based on an overall comparison, the parameters from creep and stress relaxation tests were found to be the most sensitive in describing the textural changes during thermal softening of potatoes. [source] A study on degradation kinetics of ascorbic acid in drumstick (Moringa olifera) leaves during cookingJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 11 2005Nisha P Bineesh Abstract The kinetics of ascorbic acid degradation in drumstick (Moringa olifera) leaves as well as in pure ascorbic acid solutions at the initial concentrations present in drumstick leaves over a temperature range of 50,120 °C (isothermal temperature process) has been studied. The degradation kinetics of ascorbic acid was also evaluated in normal open-pan cooking, pressure-cooking and a newly developed and patented fuel-efficient eco cooker (non-isothermal heating process). The ascorbic acid degradation followed first-order reaction kinetics where the rate constant increased with an increase in the temperature. The temperature dependence of degradation was adequately modelled by the Arrhenius equation. A mathematical model was developed using the isothermal kinetic parameters obtained to predict the losses of ascorbic acid from the time,temperature data of the non-isothermal heating/processing method. The results obtained indicate the ascorbic acid degradation is of similar order of magnitude in all the methods of cooking. Copyright © 2005 Society of Chemical Industry [source] Degradation kinetics of beetroot pigment encapsulated in polymeric matricesJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 8 2001George S Serris Abstract Kinetic studies on the degradation of water-soluble beetroot pigment, mainly consisting of the betalain betanin, encapsulated in three different matrices (pullulan and two maltodextrin samples differing in their molecular weight) were carried out under various water activity (aw,=,0.23, 0.43, 0.64, 0.75 and 0.84) and temperature (30, 40 and 50,°C) conditions. The water sorption behaviour of these materials was also examined. Degradation of the pigment was monitored by absorbance measurements at 537,nm (,max of betanin). The highest values of the rate constants for degradation were observed at an intermediate water activity level (aw,=,0.64) for all matrices and all three storage temperatures examined. An attempt to relate the degradation kinetics to the molecular mobility of the wall material was not successful. Pigment losses were observed even at temperatures below the glass transition temperature (Tg) of the polymeric matrices, although degradation was largely slowed down in the glassy state. In the vicinity of the Tg zone, where all polymers go through a glass , rubber transition, there was not a distinct change in the reaction rate, which could reflect the pronounced changes in molecular mobility of the wall material. In fact, some of the lower degradation rates were observed mostly under conditions where the matrices were fully plasticised (ie rubbery) and ,collapsed', implying that the degradation kinetics is not governed by factors related only to the physical state of the polymeric wall material. © 2001 Society of Chemical Industry [source] Thermal Degradation Kinetics of Nylon 66: Experimental Study and Comparison with Model PredictionsMACROMOLECULAR REACTION ENGINEERING, Issue 5 2007Mark A. Schaffer Abstract An experimental investigation of nonoxidative thermal degradation kinetics of nylon 66 melt under high temperature (280,300,°C) and low water content (0.02,0.14 wt.-%) conditions is presented. Experimental data for the time evolution of polymer end-group concentrations and degradation-product generation rates were compared with the predictions of the only published kinetic model. The omitted influence of water content is a plausible partial explanation for the considerable discrepancy between model predictions and some data. Several previously unreported or unquantified degradation products were identified and measured. Potential additional reactions to account for these results in future kinetic models are proposed. [source] Thermal kinetics of color degradation of mulberry fruit extractMOLECULAR NUTRITION & FOOD RESEARCH (FORMERLY NAHRUNG/FOOD), Issue 2 2003Hyung Joo Suh Abstract The effects of temperature and pH on color degradation kinetics of the mulberry fruit extract were investigated. The absorbance at 510 nm was decreased with increase of heating time, but that at 420 nm was increased with the increase of heating time at 100°C. The change of the browning index (A510/A420) was increased with increase of pH and was lower at pH 2.0 than that at pH 5.0. The browning index variation was adequately described by both the first-order and the zero-order kinetic. However, the zero-order kinetic model was proposed because of the better fit. According to the Arrhenius model, the activation energies for the browning index in the range of 80,100°C for the four different pH values were 30.68 kJ/mol for pH 2.0, 35.87 kJ/mol for pH 3.0, 42.67 kJ/mol for pH 4.0, and 43.49 kJ/mol for pH 5.0. [source] Effect of electron beam treatments on degradation kinetics of polylactic acid (PLA) plastic waste under backyard composting conditionsPACKAGING TECHNOLOGY AND SCIENCE, Issue 2 2009L. Fernando Vargas Abstract The effects of electron beam irradiation on backyard composting behaviour of polylactic acid (PLA) polymer were evaluated. Samples (10,mm2 × 0.75,mm) from thermoformed PLA drinking cups were exposed to 10,MeV electron beam irradiation at doses of 0, 72, 144 and 216,kGy. Irradiated PLA samples were placed in heat-sealed, plastic screen and added to organic feedstock in a rotating composter within a computer-controlled environmental chamber for 10 weeks at 35°C. Changes in weight, structural integrity and molecular weight were assessed over time. Results show that irradiation enhanced PLA breakdown. PLA weight decreased by increasing amounts as irradiation dose increased. Sample brittleness increased with irradiation dose and composting time. Finally, PLA molecular weight decreased as irradiation dose and compost time increased. Molecular weight D values for irradiated PLA were found to be about 430,kGy. After 1 week in a typical backyard composter, molecular weight D values increased to about 560,kGy and then fell to about 380,kGy after 2 weeks of composting. Samples irradiated at 216,kGy showed a reduction in weight of 9.4% after 10 weeks of composting, and a reduction of weight-average molecular weight of 93.7% after 6 weeks. Copyright © 2008 John Wiley & Sons, Ltd. [source] Comparison of the degradability of poly(lactide) packages in composting and ambient exposure conditionsPACKAGING TECHNOLOGY AND SCIENCE, Issue 1 2007Gaurav Kale Abstract The adoption of biodegradable polymeric materials is increasing in food and consumer goods packaging applications, due to concerns about the disposal of petroleum-based polymers and the increasing cost of petroleum-based polymer resins. Currently, poly(lactide) (PLA) polymers are the biggest commercially available bio-based polymeric packaging materials. As the main motivation for adopting biopolymers is environmental, there is a need to address the degradability and environmental performance of biodegradable packages. The aim of this study was to investigate and compare the degradation of two commercially available biodegradable packages made of PLA under real compost conditions and under ambient exposure, using visual inspection, gel permeation chromatography, differential scanning calorimetry and thermal gravimetric analysis. A novel technique to study and track the degradability of these packages under real compost conditions was used. Both packages were subjected to composting and ambient exposure conditions for 30 days, and the degradation of the physical properties was measured at 1, 2, 4, 6, 9, 15 and 30 days. PLA bottles made of 96% l -lactide exhibited lower degradation than PLA delicatessen (,deli') containers made of 94% l -lactide, mainly due to their highly ordered structure and, therefore, their higher crystallinity. The degradation rate changed as the initial crystallinity and the l -lactide content of the packages varied. Temperature, relative humidity and pH of the compost pile played an important role in the rate of degradation of the packages. First-order degradation kinetics and linear degradation trends were observed for both packages subjected to composting conditions. Copyright © 2006 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||