Navegando por Assunto "Isoterma"

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Acesso aberto (Open Access)
Adsorption capacity of phenolic compounds onto cellulose and xylan
(Universidade Federal do Pará, 2015-06) COSTA, Telma dos Santos; ROGEZ, Hervé Louis Ghislain; PENA, Rosinelson da Silva
The interaction between three phenolic compounds (catechin, caffeic acid and ferulic acid) onto two dietary fibres (cellulose and xylan) has been evaluated to inquire possible interferences on the biodisponibility of phenolic compounds. The adsorption kinetics were performed using solutions containing 100 mg/L of phenolic compounds during a contact time ranging between 10 and 120 minutes at pH 2.0, 4.5, and 7.0. After the kinetics, isotherms were obtained using phenolic compounds concentration ranging between 10 and 80 mg/L during 60 minutes, at pH 2.0 and 7.0 and temperature of 36 °C. Results indicate that adsorbed quantities mainly changed in function of pH, however the maximum adsorption was only of 0.978 mg of caffeic acid/g of xylan at pH 2 and after 60 min. Redlich-Peterson model were able to predict the adsorption isotherms of all phenolic compounds onto cellulose, except for caffeic acid at pH 7.0. The low adsorption capacities observed suggest that both dietary fibres are unable to compromise the biodisponibility of phenolic compounds, especially in the small intestine, where they are partially absorbed.
Acesso aberto (Open Access)
Aplicação de Al-PILC na adsorção de Cu2+, Ni2+e Co2+ utilizando modelos físico-químicos de adsorção
(2007) GUERRA, Denis de Jesus Lima; AIROLDI, Claudio; LEMOS, Vanda Porpino; ANGÉLICA, Rômulo Simões; VIANA, Rúbia Ribeiro
Smectite sample from the Serra de Maicuru area (Pará state, northern Brazil, Amazon region) were used for the pillaring process with Al13. Aluminum pillared clay (Al-PILC) was characterized by XRD, SEM and EDS. the textural analysis using nitrogen adsorption-desorption isotherms. The aim of this paper is to study in how Al-PILC adsorb heavy metals. The adsorption of Cu2+, Ni2+, Co2+ ions from aqueous solution in room temperature by Al-PILC have been carried out. The Langmuir, Freundlich and Temkin adsorption isotherm models have been applied to fit the experimental data, with the first model well adjusted with r = 0.999. The one-surface Langmuir equation provided the best fit to the data. The Freundlich equation presented limitations in rises concentrations, but acceptable values of parameters were obtained (Kf and n) with the use of the three models. The parameters were used to calculate the amount adsorbed Nf, a function constant Cs.
Acesso aberto (Open Access)
Aplicação de modelos matemáticos bi e tri-paramétricos na predição de isotermas de adsorção de umidade do guaraná (Paullinia cupana) em pó
(2000-04) PENA, Rosinelson da Silva; RIBEIRO, Claudio Cavalcanti; GRANDI, José Glauco
In this study, twelve mathematic models (six biparametrics and six triparametrics), applied in the prediction of isotherms, were studied on prediction of moisture adsorption isoterms of guarana (Paullinia cupana) powder obtained in spray dryer. The moisture adsorption isotherms of the product were fitted at 15° C, 25° C and 35° C, by nonlinear regression analysis, using the software STATGRAPHICS 5.1. The best results among studied models on prediction of moisture adsorption isotherms were GAB, modified BET and Anderson equations (triparametric), Handerson and Oswin equations (biparametric).
Acesso aberto (Open Access)
Aproveitamento sustentável dos resíduos de pescado para obtenção de revestimentos/filmes, aplicação na conservação pós-colheita de goiabas (psidium guajava l.), estudo da estabilidade e funcionalidade desses filmes
(Universidade Federal do Pará, 2021-03-01) PEREIRA, Glauce Vasconcelos da Silva; Calado, Verônica; LOURENÇO, Lúcia de Fátima Henriques; http://lattes.cnpq.br/7365554949786769
In the present study, a coating based on myofibrillar proteins (PML), corn starch (AM), and gum arabic (GA) were used to verify the rheological behavior and its influence on the extension of the shelf life of 'cortibel' guavas. Subsequently, the effect of the mixture PML/glycerol 10% (Gly) – coating A, and PML/Gly/GA at concentrations of 30 and 40% (w/w) of Gly, called coatings B and C, respectively, was evaluated. in the quality of 'paloma' guava. For technological characterization, the functional properties and moisture sorption behavior of PML and Gly-based films were evaluated at concentrations of 5, 10, 15, 30, and 40%. After selecting the best behavior of the PML-based films, the interactions between PML and GA were analyzed in the different proportions (10.0:0.0; 9.5:0.5; 9.0:1.0; 8 .5:1.5; 8.0:2.0 and 7.5:2.5), called E1, E2, E3, E4, E5 and E6, respectively. Among the analyzed coatings (PM; AM; GA), AM had the highest viscosity (p ≤ 0.05), followed by PML and GA, characterizing very viscous, viscous, and very diluted dispersions, respectively. The loss of mass and firmness of fruits coated with PML and AM showed lower (p ≤ 0.05) percentages on the evaluated days. Coating C (1%PML/40%Gly/1%GA) delayed the ripening rate (p ≤ 0.05) of the coated fruits. In the sorption process, films obtained curves of type II (5% glycerol) and III (10 to 40% glycerol), in which high concentrations of Gly resulted in an increase in their water content and a decrease in hysteresis until their disappearance. The E4 blend film (8.5%PML/1.5%GA/40%Gly) showed greater compatibility and integration into the structure, with low permeability to water vapor, a property required for food packaging. It is concluded that the application of coatings had a positive contribution by delaying the maturation process and increasing the commercial life of 'cortibel' and 'paloma' guavas. Fish PML films with low glycerol addition can be industrially processed and used to protect food, as they showed low hygroscopicity. The incorporation of GA in the mixed films (PML/Gli/GA) had an important effect on the technological properties, due to the interaction with myofibrillar proteins and glycerol.
Acesso aberto (Open Access)
Beneficiamento de uma argila tipo paligorskita da bacia de S. Luis-Grajaú, região de Alcântara, MA, e sua utilização como adsorvente de fósforo
(2014-03) RODRIGUES, Gabriela Monice Arruda; NEVES, Roberto de Freitas; ANGÉLICA, Rômulo Simões
This study used a sample from the basin of S. Luís-Grajaú, Maranhão state, Brazil,consisting of a mixture of predominantly palygorskite and dolomite, approaching the existence of this new occurrence, suggesting a processing method and its application as phosphorus adsorbent, once dolomite is a pH soil corrector while palygorskite has the function of nutrients carrier. First, chemical and mineralogical characterizations were performed by X-ray diffraction, X-ray fluorescence, scanning electron microscopy and separation of sand, silt and clay fractions. Sedimentation and phosphorus adsorption experiments were also performed, with determination of kinetic curve. After the X-ray diffraction analysis, results show that the sample consists mainly of palygorskite and dolomite. Illite, chlorite and quartz are also determined. It was also possible to see that the different types of disaggregation used show no significant differences in the diffraction patterns of the samples. The sand-silt-clay separation, although it is only based on the size of the material, showed a reasonable efficiency for material separation, as the sedimentation tests, where it was noticed that after 24 h, dolomite had disappeared from the supernatant. Determination of the kinetic curve revealed that the adsorption period of 2 h is not sufficient for phosphorus adsorption, requiring 24 h to reach the reaction equilibrium. Sorption tests showed efficiency higher than 91% of the initial phosphorus in solution, and the maximum quantity adsorbed per gram of sample was 0.607 mg. The correlation with the adsorption isotherm models studied, showed better results for Langmuir-Freundlich isotherm, with correlation coefficient of 0.9993, which can be attributed to the fact that adsorption occurs in more than one layer.
Acesso aberto (Open Access)
Caracterização e processamento de leite bubalino em pó em secador por nebulização
(2005-09) GUERRA, Roberta Batista; NEVES, Elisa Cristina Andrade; PENA, Rosinelson da Silva
This work aims to show the process development based on the spray dryer for the obtaining of powdered buffalo milk. For that, physiochemical analyses were made in the milk in natura and later in the powdered product, which was also submitted to microbiological analysis to be sure that it could be consumed by humans; and to sensorial analysis for obtaining information about the product's acceptance. Sorption isotherms for the powdered product were obtained at 25ºC with the purpose of perceiving the hygroscopic behavior. The buffalo's powdered milk presented the following characteristics: 3,4 % moisture content, 23,2% proteins, 46,1% fat, 4,2% ash, 0,5% soybean lecithin and 22,6% of total carbohydrates. The product was characterized as whole powdered buffalo milk, because it didn't suffer any standardization. Nutrient losses, during the process, were less then 5%, and just for proteins the variation was more than 15%. It can be justified by the desnaturation of the casein due to high temperatures (>80ºC). The powdered product presented type III sorption isotherms and the same behavior was observed for the whole powdered milk. Through sorption isotherms, the moisture content value, referent to the monolayer, was on an average of 4,4g H2O/100g dry solids, which confirms the process efficiency. The hysteresis behavior presented by the powdered product was similar of the whole powdered milk. The product acceptance was of 74%, close to the commercial powdered milk acceptance.
Acesso aberto (Open Access)
Comportamento higroscópico de partes aéreas de pimenta-de-macaco (Piper aduncum L.)
(2015-04) SILVA, Carolina de Lourdes Oliveira Cruz e; FARIA, Lênio José Guerreiro de; COSTA, Cristiane Maria Leal
Desorption isotherms of monkey pepper were determined by static gravimetric method at temperatures 35, 45, and 55 ºC, over a relative humidity range of 5.5-81%. Three mathematical models were applied to analyse the experimental data. The modified GAB model showed the best adjustment of the experimental data. The isosteric heat and differential entropy were determined by applying Clausius-Clapeyron and Gibbs-Helmholtz equations, respectively. The isosteric heat and the entropy of desorption isotherm presented similar behavior. The enthalpy-entropy compensation theory was applied to the isotherms, indicating that the aerial parts desorption mechanism are enthalpy-controlled.
Acesso aberto (Open Access)
Comportamento higroscópico do resíduo seco de camarão-rosa
(2007-12) ASSUNÇÃO, Alan Barros; PENA, Rosinelson da Silva
A study was made of the hygroscopic behavior of the dry residue of pink shrimp (Peneaus subtilis), characterized as being rich in total proteins (42.59%) and ash (22.01%). Adsorption and desorption isotherms were plotted at 10, 25 and 40 °C. The monolayer and desorption heat values were determined and thirteen mathematical models were fitted to experimental data to predict the sorption data. The product presented Type II isotherms. The adsorption data indicated that the product's microbiological stability (aw < 0.6) would require the dry residue to contain moisture of less than 13.0 g H2O.100 g–1 dry solids in adsorption and 14.0 g H2O.100 g–1 dry solids in desorption. The monolayer's desorption values indicated that, in order to avoid unnecessary loss of energy, the residue should not be dried to a moisture level below 7.29 g H2O.100 g–1 dry solids. The values of desorption heat indicated that large amounts of energy were not required to dry the residue to appropriate levels of moisture to attain microbiological stability (aw < 0.6). The best models for predicting the sorption isotherms of the residue were Oswin and Halsey (biparametric); GAB, modified BET, Hailwood-Horrobin, Anderson, Anderson-Hall and Gascoyne-Pethig (triparametric).
Acesso aberto (Open Access)
Hygroscopic behavior of buriti (Mauritia flexuosa) fruit
(2011-12) MELO, Wellington dos Santos; PENA, Rosinelson da Silva; RODRIGUES, Antonio Manoel da Cruz; SILVA, Luiza Helena Meller da
The objective of this study was to perform an analysis of the characterization of buriti fruit (Mauritia flexuosa). Each part of the fruit (peel, pulp, and fibrous part) was analyzed and their hygroscopic behavior was evaluated to establish the drying and storage conditions. Adsorption and desorption isotherms were obtained at 25 °C to the monolayer value was estimated, and the application of the Halsey, Handerson, Kuhn, Mizrahi, Oswin, Smith, BET, and GAB models was evaluated to the prediction of the isotherms. The fruit pulp was classified as rich in high quality oil, and like the peel and the fibrous part, it was also considered as rich in dietary fiber. The isotherms of the fruit parts were classified as type II, and their microbiological stability (aw< 0.6) can be maintained at 25 °C if the moisture content is lower than 8.5, 7.3, and 11.0 g H2O.100 g-1 of dry matter (d.m.), respectively. The hygroscopic behavior showed that in order to ensure stability, the fruit parts should be packaged with low water vapor permeability. The monolayer demonstrated that the peel, pulp, and the fibrous part cannot be dried under moisture content lower than 5.9, 5.0, and 6.4 g H2O.100 g-1 d.m., respectively. GAB was the most adequate model to describe their isotherms.
Acesso aberto (Open Access)
Influência da temperatura nos parâmetros de modelos bi-paramétricos que predizem isotermas de adsorção de umidade do guaraná (Paullinia cupana) em pó
(1997-12) PENA, Rosinelson da Silva; RIBEIRO, Claudio Cavalcanti; GRANDI, José Glauco
Eight biparametric mathematic models of the literature and widely applied in the prediction of moisture adsorption isoterms were analised. The guarana (Paullinia cupana) powder used in this study, was obtained in spray dryer from a hidroalcoholic extract. The experimental points of the moisture adsorption isotherms of the product at 15°C, 25°C and 35°C were fitted by non-linear regression analysis. To study temperature effect in the parameters of the models were used linear, exponential, logarithmic and inverse regressions. They were also used to fit the software STATGRAPHICS 5.1. The Handerson, Oswin and Mizrahi equations presented the best results among tested models.