Fernando Pedro Reis Brod

Evaluation of drying parameters and desorption isotherms of garden mint leaves (Mentha crispa L.)

Abstract Mint has been used as a medicinal and aromatic plant since ancient times. Its leaves are used for flavoring, tea infusions and spicing. In addition, mint oil is used to treat several diseases. In order to preserve this seasonal plant, and make it available to consumers during the whole year, it undergoes specific technological treatments, such as drying. Here the desorption isotherms of mint leaves were determined at three temperatures. Experimental curves were fitted to three two-parameter equations, three three-parameter equations and one four-parameter equation. All BET, GAB, Oswin and Peleg models could be used to describe the mint desorption isotherms. Experimental data for the drying of mint was obtained at three different temperatures and two different air velocities. The drying process was interpreted through the diffusional model in order to obtain effective diffusivity values, which proved to range from 4.765×10−13 to 2.945×10 −12 m 2 / s . Activation energy was calculated as 82928.5 J/mol assuming an Arrhenius-type temperature reliance. The empirical Page model has shown a better fit to the experimental mint drying data as compared to Ficks model, except for the 50°C–1.0 m/s curve.

Drying of pear d'Anjou with and without osmotic dehydration

Abstract This work compares the drying behavior exhibited by in natura and by osmotic dehydrated pears. The dryer was a convective vertical tray dryer. The drying was analyzed in terms of effective diffusivity and drying rates. The effective diffusivity varied from 1.59×10 −10 to 7.64×10 −10 m 2 /s for in natura pear and from 1.87×10 −10 to 8.12×10 −10 m 2 /s for the pears after osmotic dehydration. In the case of moisture content below 1.0 kg w /kg dm , the drying rates only depends on temperature, as internal resistance to moisture transfer prevails.

ESTUDO DE SECAGEM DE PÊRA BARTLETT (Pyrus sp.) EM FATIAS

The drying process aims for the reduction of the in natura products water activity, increasing the shelf life and facilitating the transport, maintenance and storage. Using a convective vertical tray drier, we obtained the drying curves of pear (nine curves) at three different temperatures (50, 60 and 70°C) and three different air velocities (0.5, 1.0 and 1.5m/s). With these results, it was possible to study the drying process determining the effective diffusivities and activation energies.

Obtenção das isotermas de sorção e modelagem matemática para a pêra bartlett (Pyrus sp.) Com e sem desidratação osmótica

Este trabalho aborda o estudo teorico-experimental da atividade de agua de peras in natura e desidratadas osmoticamente a 55oBrix e 40oC. As isotermas foram construidas para tres niveis de temperatura (40oC, 60oC e 80oC) e ajustadas pelos modelos mais usuais: Langmuir, BET, BET linear, GAB, Halsey, Oswin, Peleg, Chung e Henderson. O desvio relativo entre os valores experimentais e os valores estimados foi calculado para cada curva, a fim de se avaliar qual equacao melhor se ajustou aos dados experimentais. O modelo que melhor tratou os resultados das isotermas de dessorcao da pera foi o de Henderson entre os modelos que englobam a temperatura. Em relacao aos modelos que tratam as isotermas isoladamente, os modelos de Peleg, GAB e Oswin apresentaram o melhor ajuste para a pera desidratada e in natura.

Transferência de massa e secagem em leitos vibrofluidizados: uma revisão

Development of processing technology and equipments requires new methods and better quality of the processed product. In the continuous drying process, utilization of equipments that promotes an increment in the transfer coefficients becomes of the major interest. The use of vibrational energy has been recommended to the dispersed materials. Such method is based on the use of vibrational energy applied to disperse media. Thus, a literature review on the mass transfer and drying in vibro-fluidized beds was carried out, showing experimental results and mathematical modeling.

Aerodinâmica de leitos vibrofluidizados: uma revisão

Application of mechanical vibration to aid fluidization and to improve heat, mass and momentum transfer are usual processes in agricultural industry and it has found nowadays extensive applications in particle processing of materials difficult-to-fluidized. Equations and experimental data found in literature for the aerodynamics characteristics of vibro-fluidized beds are presented and discussed, emphasizing the vibration effect in the bed.