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This study explores the relationship between poultry farming's antibiotic administration practices and residual antibiotic levels in the litter before its application onto agricultural soils. Twenty-three antibiotics were performed across 19 Argentinean farms representing diverse antibiotic management practices. Analysis revealed up to 20 antibiotics from eight chemical classes in poultry litter samples, with tylosin, enrofloxacin, and salinomycin being the most relevant drugs. Farms with restricted antibiotic use in feed exhibited lower residual concentrations. A self-heating treatment was tested to reduce litter antibiotic levels. Although a 60 % reduction of antibiotics was found after treatment, prevalent compounds persisted at residual levels. Regulatory measures and comprehensive litter treatments pre-application are crucial to mitigate environmental risks. This is the first study that provides insight on the occurrence of >20 drugs in real poultry production scenarios from Latin America and demonstrates how relatively simple treatments can be readily applied to decrease the associated environmental risks.

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This work employed supramolecular solvents (SUPRAS) made up of octanoic acid, ethanol, and acidified water (pH ~ 3) to extract and concentrate bioactive compounds from Eugenia pyriformis Cambess (uvaia) pulp. At first, the SUPRAS phase characterization demonstrated the spherical aggregates' formation with an internal hydrophobic structure and an external hydrophilic media. Subsequently, the simultaneous production and extraction (SUPRAS-SPE) method was employed in the solid-liquid extraction (SLE) of uvaia pulp. The extracts were evaluated through Folin-Ciocalteu reducing capacity, antioxidant activity (DPPH assay), total carotenoid content (TCC), and total flavonoid content (TFC). The results showed that reducing the ethanol concentration in the SUPRAS composition boosted the TCC extraction while increasing the ethanol presence, promoting a high TFC yield. Moreover, the SUPRAS-SPE method was compared with the ex situ method (SUPRAS-ES), where the solvent was previously produced and then applied to the SLE. Both methods were evaluated concerning their EE% and thermal degradation. The SUPRAS-SPE method increased the EE% of uvaia pulp bioactive compounds compared to the SUPRAS-SE method, providing a suitable microenvironment to extract, concentrate, and stabilize carotenoids from uvaia pulp, offering a sustainable alternative to obtain valuable compounds.

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Industrial wastewater from petrochemical processes is an essential source of the synthetic phenolic phosphite antioxidant (Irgafos P-168), which negatively affects the environment. For the determination and analysis of Irgafos P-168, DSC, HPLC-MS, and FTIR methodologies were used. Solid phase extraction (SPE) proved to be the best technique for extracting Irgafos from wastewater. HPLC-MS and SPE determined the repeatability, reproducibility, and linearity of the method and the SPE of the standards and samples. The relative standard deviations, errors, and correlation coefficients for the repeatability and reproducibility of the calibration curves were less than 4.4% and 4.2% and greater than 0.99955, respectively. The analysis of variance (ANOVA), using the Fisher method with confidence in 95% of the data, did not reveal significant differences between the mentioned parameters. The removal of the antioxidant from the wastewater by SPE showed recovery percentages higher than 91.03%, and the chemical characterization of this antioxidant by FTIR spectroscopy, DSC, TGA, and MS showed it to be structurally the same as the Irgafos P-168 molecule. The recovered Irgafos was added to the polypropylene matrix, significantly improving its oxidation times. An OIT analysis, performed using DSC, showed that the recovered Irgafos-blended polypropylene (PP) demonstrated oxidative degradation at 8 min. With the addition of the Irgafos, the oxidation time was 13 min. This increases the polypropylene's useful life and minimizes the environmental impact of the wastewater.

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The COVID-19 pandemic generated a new dynamic around waste management. Personal protective equipment such as masks, gloves, and face shields were essential to prevent the spread of the disease. However, despite the increase in waste, no technical alternatives were foreseen for the recovery of these wastes, which are made up of materials that can be valued for energy recovery. It is essential to design processes such as waste to energy to promote the circular economy. Therefore, techniques such as pyrolysis and thermal oxidative decomposition of waste materials need to be studied and scaled up, for which kinetic models and thermodynamic parameters are required to allow the design of this reaction equipment. This work develops kinetic models of the thermal degradation process by pyrolysis as an alternative for energy recovery of used masks generated by the COVID-19 pandemic. The wasted masks were isolated for 72 h for virus inactivation and characterized by FTIR-ATR spectroscopy, elemental analysis, and determinate the higher calorific value (HCV). The composition of the wasted masks included polypropylene, polyethylene terephthalate, nylon, and spandex, with higher calorific values than traditional fuels. For this reason, they are susceptible to value as an energetic material. Thermal degradation was performed by thermogravimetric analysis at different heating rates in N2 atmosphere. The gases produced were characterized by gas chromatography and mass spectrometry. The kinetic model was based on the mass loss of the masks on the thermal degradation, then calculated activation energies, reaction orders, pre-exponential factors, and thermodynamic parameters. Kinetics models such as Coats and Redfern, Horowitz and Metzger, Kissinger-Akahira-Sunose were studied to find the best-fit models between the experimental and calculated data. The kinetic and thermodynamic parameters of the thermal degradation processes demonstrated the feasibility and high potential of recovery of these residues with conversions higher than 89.26% and obtaining long-chain branched hydrocarbons, cyclic hydrocarbons, and CO2 as products.

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Natural fibers used as reinforcements or fillers for materials development greatly affect properties and performance of end-use applications. As a consequence of conditioning processes such as grinding and sieving, average fiber length varies significantly. It is thus necessary to estimate the length as statistical data distribution rather than a single mean value. This approach implies length measurement of a significant number of fibers; however, a very high number of data points requires not only long-time frames but also significative amount of work. To address these issues, this article details a facile methodology to measure the length of a large number of natural fibers of oil palm empty fruit bunch (OPEFB) together with a statistical analysis to verify the correspondence between theoretical distributions and experimental data. Moreover, further information related to spectrophotometric, physico-chemical, mechanical, thermal, and morphological characteristics of OPEFB fibers coming from oil palm cultivation in Ecuador are presented. The data will contribute to comprehensively and rigorously describe the overall effects of natural fiber lengths on material properties.

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Glass fiber reinforced polymer (GFRP) bars have been increasingly used as reinforcement in concrete structures. However, when the bars are exposed to high temperatures, there is a change in the internal structure of the polymer which affects the tensile strength of the matrix and its adhesion with the fibers, reducing the mechanical strength of the bar. In addition, with increasing temperature, the bar-concrete interface is also damaged by the decomposition of hydration products from the cement paste and the loss of surface adhesion. The intensity of these changes is associated with the type of resin used as a matrix since each polymer has its own molecular structure that provides a greater or lesser ability to resist the changes imposed by temperature. The present study evaluates the mechanical behavior of reinforced concrete containing different types of GFRP bars and subjected to temperatures of 150 °C, 300 °C, and 350 °C. The GFRP bars with three types of matrices (polyester, vinyl ester, or epoxy) were mechanically evaluated under tension in two conditions: isolated and inserted into reinforced concrete specimens with a thickness of 20 mm, using two types of concrete (with and without silica fume). Degradation mechanisms at the bar/concrete interface were evaluated using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), differential thermal analysis (DTA), and bond techniques. The results showed that the type of matrix has a significant influence on the tensile behavior of GFRP bars, with the epoxy matrix showing the best performance, followed by bars with vinyl ester and polyester matrix resins. The use of silica fume improved the performance of the concrete coating and, consequently, improved the protection of GFRP bars, hindering the diffusion of oxygen and heat; bar/concrete adhesion was compromised by thermal degradation of GFRP bar ribs.

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Kenaf (Hibiscus cannabinus L.) is one of the most investigated and industrially applied natural fibers for polymer composite reinforcement. However, relatively limited information is available regarding its epoxy composites. In this work, both thermal and chemical properties were, for the first time, determined in kenaf fiber reinforced epoxy matrix composites. Through XRD analysis, a microfibrillar angle of 7.1° and crystallinity index of 44.3% was obtained. The FTIR analysis showed the functional groups normally found for natural lignocellulosic fibers. TMA analysis of the composites with 10 vol% and 20 vol% of kenaf fibers disclosed a higher coefficient of thermal expansion. The TG/DTG results of the epoxy composites revealed enhanced thermal stability when compared to plain epoxy. The DSC results corroborated the results obtained by TGA, which indicated a higher mass loss in the first stage for kenaf when compared to its composites. These results might contribute to kenaf fiber composite applications requiring superior performance.

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In this study, blends of poly(lactic acid) (PLA)/linear medium density polyethylene (LMDPE) at different weight ratios were prepared by rotational molding. Two mixing strategies were used to evaluate the effect of phase dispersion on the physical and mechanical properties: (i) Dry-blending (DB) using a high shear mixer, and (ii) melt-blending (MB) using a twin-screw extruder. Thermal, morphological, and mechanical analyses were performed on the neat polymers and their blends. The thermal analysis was completed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), and the blends prepared by MB had lower thermal stability than the ones prepared via DB due to some thermo-oxidative degradation through the double thermal process (extrusion and rotomolding). The morphology of the rotomolded parts showed that DB generated larger particle sizes (around 500 µm) compared to MB (around 5 µm) due to the shear and elongational stresses applied during extrusion. The tensile and flexural properties of the rotomolded parts combined the PLA stiffness with the LMDPE toughness independent of the blending technique. Neat PLA presented increments in tensile strength (54%) and flexural strength (111%) for DB compared with MB. A synergistic effect in impact strength was observed in blends with 12 and 25 wt. % of PLA prepared by DB.

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The kinetics of thermal degradation of ß-chitin extracted from Dosidicus gigas squid pen, was studied at normal conditions as well as after being subjected to the action of high-pressure impact of 9.7 GPa. The integral iso-conversional procedure of Kissinger-Akahira-Sunose (KAS) recommended by the ICTAC kinetics committee was applied to the non-isothermal data obtained from thermogravimetry (TGA). Lifetimes were predicted without assumption of any reaction model. Heating rates of ß = 10, 15, 20 and 25 °C/min under nitrogen atmosphere were used from room temperature to 1300 °C. A comparative study with α-chitin was performed. All the samples were structurally and chemically characterized by several techniques. The extracted ß-chitin was found to be in the monohydrate form; while with the action of high-pressure impact, it was transformed into ß-chitin dehydrate showing slightly higher stability. Reliable prediction for lifetimes considering working temperatures over 425 K was found for α and ß-chitin.

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The 25R-NBOH family is a group of thermally labile compounds that are relevant for forensic sciences and traditionally analyzed by GC-MS after derivatization - a step that is time consuming in a routine work. In this paper, the use of short analytical columns (4 and 10 m) showed to decrease compound degradation in the GC oven during chromatographic separation and to allow the analysis of non-derivatized 25R-NBOH compounds by GC-MS. A shorter column demanded a higher gas flow rate, and both factors decreased residence time of the analytes in the column and their degradation. The inlet temperature (250° C or 280°C) did not impact the response of 25R-NBOH. A 25R-NBOH fragmentation pathway by electron ionization was also presented for the first time. The GC-MS method with a 4 m column was successfully applied to other compounds of forensic interest, and it can be tested in the analysis of biological samples in toxicological investigations.

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The use of chemometric tools is progressing to scientific areas where analytical chemistry is present, such as food science. In analytical food evaluation, oils represent an important field, allowing the exploration of the antioxidant effects of herbs and seeds. However, traditional methodologies have some drawbacks which must be overcome, such as being time-consuming, requiring sample preparation, the use of solvents/reagents, and the generation of toxic waste. The objective of this study is to evaluate the protective effect provided by plant-based substances (directly, or as extracts), including pumpkin seeds, poppy seeds, dehydrated goji berry, and Provençal herbs, against the oxidation of antioxidant-free soybean oil. Synthetic antioxidants tert-butylhydroquinone and butylated hydroxytoluene were also considered. The evaluation was made through thermal degradation of soybean oil at different temperatures, and near-infrared spectroscopy was employed in an n-way mode, coupled with Parallel Factor Analysis (PARAFAC) to extract nontrivial information. The results for PARAFAC indicated that factor 1 shows oxidation product information, while factor 2 presents results regarding the antioxidant effect. The plant-based extract was more effective in improving the frying stability of soybean oil. It was also possible to observe that while the oxidation product concentration increased, the antioxidant concentration decreased as the temperature increased. The proposed method is shown to be a simple and fast way to obtain information on the protective effects of antioxidant additives in edible oils, and has an encouraging potential for use in other applications.

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ZnO particles were synthetized by the sol-gel method and subsequent heat treatment of 400, 500 and 600 °C was applied. The nano ZnO particles were incorporated to the unsaturated polyester resin by solution blending at 0.05 wt % concentration. X-ray diffraction detected the formation of a wurtzite-like structure. Viscoelastic behavior of neat polyester and nanocomposites revealed the nano ZnO particles does not promote better mechanical properties because of a weak interaction and the glass transition temperature of the polyester was favored by the presence of a higher quantity of nano-size ZnO particles. Thermogravimetric analysis at 5, 10 and 20 °C/min allowed determining the degradation kinetic parameters based on the Friedman and Kissinger models for neat polyester and nanocomposites. Heating rates promoted an increase in the temperature degradation and the addition of ZnO particles promoted a catalyst effect that reduce the amount of thermal energy needed to start the thermal degradation.

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Hyaluronic acid (HA) is a macromolecule with valuable benefits over its range of molar masses (MM). Degradation studies are relevant to maintain the same purity level in biomedical studies when using HA of different MM. We degraded HA via high pH and temperature and evaluated its MM, solution behavior, and structure over time. After 24 h, low MM HA was predominant, and the MM decreased from 753 to 36.2 kDa. Dynamic light scattering (DLS) showed a decrease in the number of HA populations, and the solution tended to be less polydispersed. The zeta potential varied from - 10 to - 30 mV, close to the stable range. FTIR showed that the primary structure of HA was affected after only 48 h of reaction. These results are relevant for the production of low MM HA to be used or mixed with high MM HA, generating structured biomaterials for biomedical applications.

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The aim of this work was to study the effects of temperature and time of oven drying and hot water cooking processes on HCN (hydrocyanic acid) degradation of cassava leaves as a contribution for obtaining a safe product for human consumption. Nine varieties of cassava leaves collected in the Amazonian region of Brazil (Pará State) were characterized regarding moisture, pH, total acidity, ashes, total lipids, total protein, water activity, carbohydrates, total energetic value and HCN contents. The leaves of the three cassava varieties, which presented the highest HCN contents, were submitted to the thermal degradation of HCN, under drying and boiling conditions. All the leaves presented similar physicochemical characteristics and the HCN contents varied from 90.6 to 560.9 mg HCN/kg fresh leaves (total HCN) and from 16.6 to 59.2 mg HCN/kg fresh leaves (free HCN). Thermal degradation studies on HCN showed that the drying and boiling processes were effective on total HCN removal after 180 min. Furthermore, a remarkable decrease in HCN contents was observed after 20 min of boiling. Regarding free HCN, the drying method was more effective than boiling, showing high degradation percentages: 74.1%-92.2% to 1.1%-72.4%, respectively.

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The pelleting of forest and agricultural materials, mainly because many residues from both industries can be used in this process, has been an alternative in obtaining added value products to energy generation. Thus, the aim of this study was to evaluate the energy quality of the pellets produced from forest and agricultural residues as raw materials and to verify the utility of the thermogravimetric analysis (TGA) and the differential thermogravimetric analysis (DTG) in characterizing the behavior of the pellets during the combustion process. Four residues were used: (1) Pinus spp. woodchips, (2) apple pruning residues, (3) aciculated dry branches of Araucaria angustifolia and (4) A. angustifolia empty-seeds. Chemical composition of the raw materials was determined and the physical and energetic properties of the pellets were analysed. Plus, the proximate analysis of the pellets was carried out. The samples were submitted to TGA with a heating rate of 20ºC min-1 from room temperature to 1000ºC, in a N2 atmosphere. The variation of chemical composition of each residue was determinant in the characterization of each stage of the thermal degradation. Stages and events of the degradation were closely linked to the chemical and energetic nature of the samples. Use of TGA to characterize the thermal degradation of the pellets produced with different forest and agricultural residues was demonstrated as an efficient technique to quantify and qualify the events that occurred in each stage of the combustion of these biofuels.(AU)

A peletização de resíduos florestais e agrícolas tem sido uma alternativa na obtenção de produtos com maior valor agregado para a geração de energia, pois muitos resíduos podem ser utilizados neste processo. Assim, o objetivo deste estudo foi avaliar a qualidade energética dos pellets produzidos com resíduos florestais e agrícolas como matéria-prima e verificar a viabilidade de uso da análise termogravimétrica (TGA) e análise termogravimétrica diferencial (DTG) para caracterizar o comportamento dos pellets durante o processo de combustão. Foram utilizados quatro resíduos: (1) partículas de Pinus spp., (2) resíduos de poda de maçã, (3) ramos secos aciculados de Araucaria angustifolia e (4) falhas de pinhão de A. angustifolia. Foram determinadas a composição química das matérias-primas e analisadas suas propriedades físicas e energéticas, bem como a análise imediata dos pellets. As amostras foram submetidas ao TGA com uma taxa de aquecimento de 20ºC min-1 da temperatura ambiente a 1000ºC, em atmosfera de N2. As curvas termogravimétricas permitiram a avaliação da perda de massa em função da temperatura. O DTG permitiu a avaliação da taxa de perda de massa. A variação na composição química de cada resíduo foi determinante para caracterizar cada estágio da degradação térmica. Os estágios e os eventos de degradação estavam intimamente ligados à natureza química e energética das amostras. O uso de TGA, para caracterizar a degradação térmica dos pellets produzidos com diferentes resíduos florestais e agrícolas, se mostrou eficiente para quantificar e qualificar os eventos que ocorreram em cada estágio de combustão desses biocombustíveis.(AU)

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ABSTRACT: The pelleting of forest and agricultural materials, mainly because many residues from both industries can be used in this process, has been an alternative in obtaining added value products to energy generation. Thus, the aim of this study was to evaluate the energy quality of the pellets produced from forest and agricultural residues as raw materials and to verify the utility of the thermogravimetric analysis (TGA) and the differential thermogravimetric analysis (DTG) in characterizing the behavior of the pellets during the combustion process. Four residues were used: (1) Pinus spp. woodchips, (2) apple pruning residues, (3) aciculated dry branches of Araucaria angustifolia and (4) A. angustifolia empty-seeds. Chemical composition of the raw materials was determined and the physical and energetic properties of the pellets were analysed. Plus, the proximate analysis of the pellets was carried out. The samples were submitted to TGA with a heating rate of 20ºC min-1 from room temperature to 1000ºC, in a N2 atmosphere. The variation of chemical composition of each residue was determinant in the characterization of each stage of the thermal degradation. Stages and events of the degradation were closely linked to the chemical and energetic nature of the samples. Use of TGA to characterize the thermal degradation of the pellets produced with different forest and agricultural residues was demonstrated as an efficient technique to quantify and qualify the events that occurred in each stage of the combustion of these biofuels.

RESUMO: A peletização de resíduos florestais e agrícolas tem sido uma alternativa na obtenção de produtos com maior valor agregado para a geração de energia, pois muitos resíduos podem ser utilizados neste processo. Assim, o objetivo deste estudo foi avaliar a qualidade energética dos pellets produzidos com resíduos florestais e agrícolas como matéria-prima e verificar a viabilidade de uso da análise termogravimétrica (TGA) e análise termogravimétrica diferencial (DTG) para caracterizar o comportamento dos pellets durante o processo de combustão. Foram utilizados quatro resíduos: (1) partículas de Pinus spp., (2) resíduos de poda de maçã, (3) ramos secos aciculados de Araucaria angustifolia e (4) falhas de pinhão de A. angustifolia. Foram determinadas a composição química das matérias-primas e analisadas suas propriedades físicas e energéticas, bem como a análise imediata dos pellets. As amostras foram submetidas ao TGA com uma taxa de aquecimento de 20ºC min-1 da temperatura ambiente a 1000ºC, em atmosfera de N2. As curvas termogravimétricas permitiram a avaliação da perda de massa em função da temperatura. O DTG permitiu a avaliação da taxa de perda de massa. A variação na composição química de cada resíduo foi determinante para caracterizar cada estágio da degradação térmica. Os estágios e os eventos de degradação estavam intimamente ligados à natureza química e energética das amostras. O uso de TGA, para caracterizar a degradação térmica dos pellets produzidos com diferentes resíduos florestais e agrícolas, se mostrou eficiente para quantificar e qualificar os eventos que ocorreram em cada estágio de combustão desses biocombustíveis.

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The effect of temperature on the degradation of anthocyanins in juçara and "Italia" grape extracts was determined between 50 and 90°C. For both species, thermal degradation followed a first-order kinetic model. The decimal reduction time decreased with increasing temperature, and dependence on the thermodegradable factor was lower at higher temperatures. The anthocyanins from juçara degraded more slowly than those extracted from "Italia" grapes. The activation enthalpy and free energy of inactivation indicated an endothermic reaction, not spontaneous degradation, whereas the activation entropy suggested that the transition state has less structural freedom than that of the reactants. The antioxidant capacity of the extracts was reduced when subjected to 90°C heat treatment, however, significant quantities of this bioactive compound still remained.

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Interest in biodegradable edible films as packaging or coating has increased because their beneficial effects on foods. In particular, food products are highly dependents on thermal stability, integrity and transition process temperatures of the packaging. The present work describes a complete data of the thermal degradation and dynamic mechanical properties of starch-glycerol based films with citric acid (CA) as crosslinking agent described in the article titled: "Biodegradable and non-retrogradable eco-films based on starch-glycerol with citric acid as crosslinking agent" González Seligra et al. (2016) [1]. Data describes thermogravimetric and dynamical mechanical experiences and provides the figures of weight loss and loss tangent of the films as a function of the temperature.

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Effects of bleaching (70 C, 2 minutes), pasteurization (75 C, 30 minutes), and freezing (-5 or -18 C)on the physicochemical characteristics (pH, titratable acidity and soluble solids), and on carotenoids of araticum pulp were evaluated during the 180-day storage. Carotenoids were analyzed by high performance liquid chromatography. The fresh pulp showed high contents of soluble solids (21.27 Brix), all-trans--carotene (1.98 mg/100 g), all-trans--carotene (1.58 mg/100 g) and vitamin A value (131.46 RAE/100 g) when compared to other fruits from Cerrado. The physicochemical characteristics of pulp remained unchanged after pasteurization and bleaching, and during the storage (p > 0.05). Thermal treatments equally decreased the all-trans--carotene, all-trans--carotene contents, and vitamin A value (average: -18, -41 and -41 % respectively). Both freezing temperatures influenced on the pulps in similar manner (p > 0.05). Carotenoids and vitamin A value of the bleached or pasteurized and frozen (-5 or -18 C) pulps varied similarly up to 90 days of storage. At 180 days, all-trans--carotene and all-trans--carotene contents and vitamin A value increased in pasteurized pulps (in average +6.5 %, +33.0 % and +33.5 %, respectively), and they decreased in bleached pulps (-23.5 %, -19.5 % and -19.5 %, respectively). Bleaching/freezing binomial was effective for pulp storage up to 90 days; and, after this period it is recommended the use of pasteurization/freezing approach(AU)

Avaliaram-se os efeitos da pasteurização (75 C, 30 minutos), branqueamento (70 C, 2 minutos) e congelamento (-5 C ou -18 C) nas características físico-químicas (acidez titulável, pH e sólidos solúveis) e nos carotenoides de polpa de araticum durante 180 dias de armazenamento. Os carotenoides (all-trans--caroteno e all-trans--caroteno) foram analisados por cromatografia líquida de alta eficiência. A polpa in natura apresentou elevado teor de sólidos solúveis (21,27 Brix), all-trans--caroteno (1,98 mg/100 g), all-trans--caroteno (1,58 mg/100 g) e do valor de vitamina A (131,46 RAE/100 g) quando comparados a outros frutos do Cerrado. A pasteurização, o branqueamento e o armazenamento não modificaram as características físico-químicas da polpa. Os tratamentos térmicos diminuíram igualmente (p > 0,05) os teores de all-trans--caroteno, all-trans--caroteno e valor de vitamina A (média: 18, -41 e -41 %, respectivamente). Os carotenoides e o valor de vitamina A nas polpas branqueadas, pasteurizadas e congeladas a -5 C ou -18 C variaram similarmente até 90 dias de armazenamento. Aos 180 dias de armazenamento, os teores de all-trans--caroteno e all-trans--caroteno e o valor de vitamina A aumentaram nas polpas pasteurizadas (média: +6,5 %, +33,0 % e +33,5 %, respectivamente) e reduziram nas polpas branqueadas (-23,5 %, -19,5 % e -19,5 %, respectivamente). O binômiobranqueamento/congelamento mostrou-se eficaz para armazenamento da polpa por até 90 dias; após esse período, recomenda-se o uso da pasteurização/congelamento(AU)

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This paper reports on a study of the influence of sodium alginate concentration and iron addition on the ion exchange kinetics of calcium alginate ferrogel beads produced by external gelation. The calcium absorption and sodium release of the beads were fitted to Fick's second law for unsteady state diffusion in order to obtain the effective diffusion coefficients of Na(+) and Ca(2+). The dried beads were characterized concerning their thermal stability, particle size distribution and morphology. The gelation kinetics showed that an increase in alginate concentration from 1% to 2% increased the Ca(2+) equilibrium concentration, but presented no effect on Ca(2+) effective diffusion coefficient. Alginate concentration higher than 2% promoted saturation of binding sites at the bead surfaces. The addition of iron promoted faster diffusion of Ca(2+) inside the gel beads and reduced the Ca(2+) equilibrium concentration. Also, iron particles entrapped in the alginate gel beads promoted greater absorption of water compared to pure alginate gel and lower thermal stability of the beads. The main diffusion of Ca(2+) into and Na(+) out from the bead took place during the first 60 min, during which almost 85-90% of the Ca(2+) equilibrium concentration is achieved, indicating that this period is sufficient to produce a Ca-alginate bead with high crosslinking of the polymer network.

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