Marcio Arêdes Martins

Análise da hidratação do arroz na parboilização

The aim of this work was to study the water uptake phenomenon during soaking of husk rice (IRGA 424) under different temperatures. Grains of husk rice with initial water content of 0.1364 (d.b.) imbibed in distilled water at temperatures of 35, 45, 55, and 75 oC were used. A temperature increase resulted in an increase in the water absorption rate. The Pelegs model fitted satisfactory to the experimental data of water absorption kinetics. The effective diffusion coefficient increased with an increase in temperature ranging from 0.80 to 9.18 x 10-11 m2/s. The dependency of the effective diffusion coefficient on temperature can be described by the Arrhenius relationship for the temperature range studied, activation energy of 33.2 kJ.mol-1.The aim of this work was to study the water uptake phenomenon during soaking of husk rice (IRGA 424) under different temperatures. Grains of husk rice with initial water content of 0.1364 (d.b.) imbibed in distilled water at temperatures of 35, 45, 55, and 75 oC were used. A temperature increase resulted in an increase in the water absorption rate. The Pelegs model fitted satisfactory to the experimental data of water absorption kinetics. The effective diffusion coefficient increased with an increase in temperature ranging from 0.80 to 9.18 x 10-11 m2/s. The dependency of the effective diffusion coefficient on temperature can be described by the Arrhenius relationship for the temperature range studied, activation energy of 33.2 kJ.mol-1.

Periods of constant and falling-rate for infrared drying of carrot slices

The aim of this work was to study the infrared drying process of carrot slices and to determine coefficients related to the heat and mass transfer of the process. Fresh carrots were used, dried until constant weight in a dryer with infrared heating source. Different models were utilized to fit the experimental data of constant and falling drying rate periods. It was verified that the coefficients of heat and mass transfer, during the constant drying rate, significantly increased with temperature on rise. The Diffusion Approximation, Two Terms, Midili and Verna models satisfactory represented the falling period of drying rate of carrot slices. The effective diffusion coefficient increased with temperature and this relationship can be represented by the Arrhenius equation, obtaining activation energy to the drying process of 29.092 kJ mol -1

Diffusion and sorption of allyl isothiocyanate in the process of fumigation of maize

The purpose of this work was to evaluate the transport of allyl isothiocyanate (AITC) by means of the sorption mechanism and the diffusion of AITC through maize grains. The experimental procedure to study the sorption mechanism was conducted by injection of AITC in glass flasks containing the grains. Kinetic models of zero, first and second order were fitted to AITC concentration data, with the purpose of determining the sorption rate (k). For the study of diffusion, a prototype was utilized in which the components are a gas chamber and a cylindrical column in which the grains were stored. At the interval of 110 min, samples in the chamber and in the column were collected, which were immediately injected into the gas chromatograph. In order to determine the effective diffusion coefficient (Def) of AITC through maize grains, the term referring to the sorption rate was added to the diffusion equation. The kinetic model of the first order was the one that best fitted the experimental data for the sorption mechanism, and k was 6.26 x 10-4 s-1. The Def of AITC through grains was 7.2 x 10-3 cm2 s-1. It was concluded that the transport of AITC through maize grains is slow, due to the low value of Def and high sorption rate of this component by the grains.

Effects of the mechanical damage on the water absorption process by corn kernel

The purpose of this study was to investigate and model the water absorption process by corn kernels with different levels of mechanical damage Corn kernels of AG 1510 variety with moisture content of 14.2 (% d.b.) were used. Different mechanical damage levels were indirectly evaluated by electrical conductivity measurements. The absorption process was based on the industrial corn wet milling process, in which the product was soaked with a 0.2% sulfur dioxide (SO2) solution and 0.55% lactic acid (C3H6O3) in distilled water, under controlled temperatures of 40, 50, 60, and 70 oC and different mechanical damage levels. The Peleg model was used for the analysis and modeling of water absorption process. The conclusion is that the structural changes caused by the mechanical damage to the corn kernels influenced the initial rates of water absorption, which were higher for the most damaged kernels, and they also changed the equilibrium moisture contents of the kernels. The Peleg model was well adjusted to the experimental data presenting satisfactory values for the analyzed statistic parameters for all temperatures regardless of the damage level of the corn kernels.

Three-Dimensional Modeling and Simulation of Heat and Mass Transfer Processes in Porous Media: An Application for Maize Stored in a Flat Bin

If the relative humidity and temperature of the air inside a granular mass of stored grain exceeds a certain threshold value, microorganism activity is likely to increase. Lower relative humidity and temperature, when uniformly distributed inside the grain mass, prevent moisture migration and an increase in microorganism activity. To cool down or maintain the temperature of the grain mass below a threshold value, forced ventilation with an appropriate airflow can be used to remove excess moisture or heat generated by grain or microorganism respiration. The objective of this work was to solve the equations that describe the conservation of heat, mass, and momentum in order to predict heat and mass transfer processes in the environment inside a grain mass of maize, stored in a flat bin. Three-dimensional computational fluid dynamics was used to solve the equations. The analysis of heat and mass transfer was performed considering the geometry of a two-ton-capacity bin prototype using a hexahedral mesh for the finite volume analysis. The numerical grid was defined to discretize the physical flow domain of interest to calculate velocity, temperature, and moisture distribution in the bulk of stored grain. The predicted results were compared with experimental data, and the agreement between them was very good.

Kinetics and Thermodynamics of Oil Extraction from Jatropha curcas L. Using Ethanol as a Solvent

In the study the yield and kinetic and thermodynamic parameters of the oil extraction process from Jatropha curcas L. using ethanol as a solvent were evaluated for different temperatures, moisture contents of the solid phase, and particle sizes. The extraction process yield increased with contact time of solid particles with the solvent until reaching equilibrium (saturation of the solvent), for all the temperatures, moisture contents, and average particle sizes. These parameters significantly influenced (95% confidence) the extracted oil yield. A convective mass transfer model was used to simulate the extraction process and estimate the kinetic and thermodynamic parameters. For all conditions evaluated, values of oil yield in the liquid phase close to equilibrium were obtained in approximately 20 min. The variations of enthalpy and entropy were positive, indicating that the process is endothermic and irreversible. Values obtained for the variation in Gibbs free energy showed that the extraction process using ethanol as a solvent is spontaneous and thermodynamically favorable for the moisture content of 0%, where the smaller the average particle size the greater the spontaneity of the process.

Rheological behavior of Chlorella sp. e Scenedesmus sp. cultures in different biomass concentrations

Studies involving the use of microalgae are increasingly intensifying for the potential they present to produce biofuels, because they are a renewable energy source that does not compete directly with food production, and because they enable the obtaining of a fuel with less environmental impact when compared to fossil fuel. In this context, the use of microalgae is directly associated to its capacity to be produced on a large scale and to be extracted from the culture medium. Rheological studies are important for obtaining the information needed in the elaboration of projects and equipment that will be used in various operations existing in systems of production and extraction of algal biomass. In the evaluation of different levels of dry biomass concentration, studies have been conducted of the rheological behavior of cultures of Chlorella sp. BR001 and Scenedesmus sp. BR003. The Power Law model adjusted well to the data of shear stress as a function of strain rate. In all concentrations the cultures showed non-Newtonian behavior. It was observed to Scenedesmus sp. BR003 little effect of biomass concentration on the apparent viscosity and shear stress.

Perda de matéria seca em grãos de milho armazenados em bolsas herméticas

The aim of this study was to evaluate the quality and loss of dry matter of corn grain stored in airtight bags at different temperatures. To do this, corn grain with an initial moisture content of 14.8 and 17.9% was placed into polyethylene bags which were sealed and stored at temperatures of 15, 25 and 35 °C. For 150 days, at 30-day intervals, the concentrations of oxygen (O2) and carbon dioxide (CO2) in the bags were measured, and grain samples were taken to determine the moisture content, apparent specific dry matter weight, percentage of germination and commercial classification. Dry matter loss was estimated by means of a model obtained as a function of the respiratory rate of the grains. At 150 days, the loss of dry matter of the corn grains with a moisture content of 14.8% when stored, was approximately 3.5 times lower than that of the product with a moisture content of 17.9% when stored. Based on the results of the percentage of germination and apparent specific dry matter weight, the limit of a 0.015% loss in dry matter can be considered as the maximum permissible to maintain the integrity of corn grain in storage in sealed bags. At 150 days, only the corn grain, stored with moisture content of 17.9% and at a temperature of 35 °C, showed a lower classification (Type 2) than at the beginning of the experiment, and this condition coincided with a dry matter loss of 0.037 %.The aim of this study was to evaluate the quality and loss of dry matter of corn grain stored in airtight bags at different temperatures. To do this, corn grain with an initial moisture content of 14.8 and 17.9% was placed into polyethylene bags which were sealed and stored at temperatures of 15, 25 and 35 °C. For 150 days, at 30-day intervals, the concentrations of oxygen (O 2 ) and carbon dioxide (CO 2 ) in the bags were measured, and grain samples were taken to determine the moisture content, apparent specific dry matter weight, percentage of germination and commercial classification. Dry matter loss was estimated by means of a model obtained as a function of the respiratory rate of the grains. At 150 days, the loss of dry matter of the corn grains with a moisture content of 14.8% when stored, was approximately 3.5 times lower than that of the product with a moisture content of 17.9% when stored. Based on the results of the percentage of germination and apparent specific dry matter weight, the limit of a 0.015% loss in dry matter can be considered as the maximum permissible to maintain the integrity of corn grain in storage in sealed bags. At 150 days, only the corn grain, stored with moisture content of 17.9% and at a temperature of 35 °C, showed a lower classification (Type 2) than at the beginning of the experiment, and this condition coincided with a dry matter loss of 0.037 %.

Acúmulo de matéria seca e óleo nas sementes de pinhão-manso e qualidade do óleo extraído

Objetivou-se, com o presente trabalho, avaliar o efeito do estadio de maturacao dos frutos sobre o rendimento em massa de materia seca e oleo das sementes de pinhao-manso (Jatropha curcas L.) , e sobre a qualidade do oleo extraido. Frutos de pinhao-manso foram classificados em quatro diferentes estadios de maturacao, de acordo com sua coloracao: verde, amarela, marrom-amarela e marrom. Amostras dos frutos de cada estadio foram retiradas para a determinacao do teor de agua, dimensoes principais, volume e contagem de sementes por fruto. As sementes foram extraidas para determinacao do teor de agua, dimensoes principais, volume, massa seca de mil sementes, percentual em massa de oleo e percentual de acidos graxos livres do oleo extraido. A colheita de frutos de pinhao-manso com coloracao marrom-amarelo e marrom, proporcionou maior rendimento em massa seca das sementes e em conteudo de oleo. A colheita dos frutos com coloracao marrom-amarelo alem de possibilitar bons rendimentos em oleo e em materia seca, permite a obtencao de oleo com indice de acidez menor, sendo o estadio de maturacao mais indicado para a realizacao da colheita dos frutos e sementes de pinhao-manso para fins industriais.

Pear Drying: Thermodynamics Studies and Coefficients of Convective Heat and Mass Transfer

Abstract The objective of this work was to study the convective drying process used for cylindrical samples of two different pear varieties, one originating from Europe (Pyrus communis) and the other from Asia (Pyrus pyrifolia), submitted to two blanching treatments, as well as determine some coefficients referring to heat and mass transfer and thermodynamic parameters of the process, being: enthalpy (ΔH*), entropy (ΔS*) and Gibbs energy of activation (ΔG*). All samples were dried in a forced air oven at temperatures of (62, 76, 84 and 92)°C until reaching a constant mass. The heat and mass transfer coefficients referring to the constant and falling-rate drying periods were obtained by adjusting the experimental data to wet bulb temperature and liquid diffusion models, respectively. The heat and mass transfer coefficients varied linearly with temperature. Blanching altered the drying behavior of the two varieties in relation to the non-blanched samples, mainly at the elevated drying temperatures of 84°C and 92°C. ΔH* and ΔS* decreased while ΔG* increased with the elevation of drying temperature; therefore, it was possible to verify that variation in the diffusion process in pears during drying is dependent on energetic contributions of the environment.