Satoshi Tobinaga

Diffusive model with shrinkage in the thin-layer drying of fish muscles

ABSTRACT Fish fillets present large variation in volume during drying, due to their high initial moisture content. A kinetical study on the drying of fish muscles in slabs shaped with constant air conditions at three temperature levels is presented. For the modeling of the drying process of these materials, a diffusive model can be used, assuming a one-dimensional volume change. A linear correlation was considered between the thickness of the material and its moisture content, where the linear shrinkage coefficient has been determined. The resulting dimensionless nonlinear partial differential equation was solved numerically by the finite differences technique.

A diffusion model for describing water transport in round squid mantle during drying with a moisture-dependent effective diffusivity

To date, only experimental drying studies have been published for the drying of squid mantle, neglecting the transport phenomenon of water in squid muscle. Added to this, the published studies of mass transfer phenomena during the drying of fish and other seafoods are always based on Ficks second law for evaluating constant effective diffusivity. Therefore, the dependence of the latter transport property on the moisture of muscle is unknown. This work studies the mass transfer of water during the drying of squid mantle (Loligo brasiliensis), previously salted and smoked by liquid smoking (hickory extract), where the effective diffusivity was taken as an exponential function of moisture. The results thus obtained were compared with values calculated from the slope method. The model, based on the Ficks second law and solved by the finite difference explicit method, was applied to a hollow cylinder geometry (round squid mantle) without considering the shrinkage.

Otimização do processo de secagem osmótica na obten ção de produtos secos da manga Tommy Atkins

Tropical fruits like mango (Mangifera indica L.), one of the most popular fruits of the world, although very much appreciated, is highly perishable and seguire special techniques for its conservation and commercialization. This work had as objective to optimize the process of osmotic drying of mango and to study the effect of the temperature, sucrose concentration and time of immersion on the loss of water and gain in solid content. The influence of each variable and its interactions on the response were analyzed through analysis of variance (F-test and determination coefficient). It was verified that the three factors show significant effect on the loss of water and gain of mango solids, within the limits of the study. The optimum condition found for dehydration used as pretreatment for larger loss of water and smaller gain of solids was: temperature of 50 oC, concentration of 40% and immersion time of 90 min.

Theoretical and Experimental Study of Water Transport in a Hollow Cylinder Applied to the Drying of Round Squid Mantle

ABSTRACT Until now, attention has been focused solely in the drying of squid mantle from an experimental point of view, neglecting the transport phenomenon studies of water in squid muscle. This work studies the drying of squid mantle (Loligo brasiliensis), previously salted and smoked by liquid smoking (hickory extract), using a tubular dryer in closed cycle with a silicagel fixed bed in series. The mass transfer phenomenon during drying was studied, based on the Ficks second law, with the effective diffusivity supposed constant, which enabled an analytical solution to the problem. The drying curve calculated with the resulting equation was compared with experimental data. The model was applied to a hollow cylinder geometry (round squid mantle), with its internal surface isolated from the drying environment by a plastic film. The latter was given a tubular form and introduced inside the mantle cavity (impervious wall boundary condition).

Otimização da desidratação osmótica de filés de mapará (Hypophthalmus edentatus) através da metodologia de superfície de resposta

A desidratacao osmotica de files de mapara tem sido utilizada como pre-tratamento antes da secagem e refrigeracao de alimentos como um meio de reduzir a umidade dos produtos. O objetivo do trabalho foi otimizar a transferencia de massa ocorrida durante a desidratacao osmotica de mapara atraves da metodologia de superficie de resposta. A desidratacao osmotica foi realizada de acordo com um planejamento fatorial completo 23, com oito pontos fatoriais, tres centrais e seis axiais, totalizando 17 ensaios, em que o valor das variaveis dependentes, a perda de peso (PP), a perda de agua (PA), o ganho de solidos (GS), GS/PA e acido tiobarbiturico (TBA), sao funcoes das variaveis independentes, temperatura, concentracao de NaCl e tempo de imersao. A analise estatistica aplicada aos dados experimentais foi realizada atraves do erro puro e pelo SS residual. Aplicando a metodologia de superficie de resposta, a condicao otima de convergencia de menor perda de peso, maior perda de agua e menor ganho de sal correspondeu a uma concentracao de cloreto de sodio de 22%, temperatura de 46 °C e tempo de 7 horas.

Análise sensorial de músculo de mapará com e sem tratamento osmótico

O objetivo deste trabalho foi avaliar sensorialmente o mapara in natura e com pre-tratamento osmotico antes da secagem. Para o teste de aceitabilidade do bolinho de musculo de mapara, foram utilizados peixes in natura e desidratados osmoticamente, nas melhores condicoes de processo, em solucoes de NaCl, NaCl + sacarose e em solucao de NaCl + xarope de milho e secos. Foram utilizados 25 provadores nao treinados, de ambos os sexos, com idade variando de 20 a 60 anos. Os atributos sensoriais avaliados foram aparencia, aroma, sabor, textura e impressao global. O aroma e a textura das amostras com e sem pre-tratamento osmotico foram os atributos que obtiveram maior aceitacao por parte dos consumidores. Pode-se concluir que as amostras tratadas com solucoes osmoticas, com excecao das tratadas com solucao de NaCl + xarope de milho, proporcionaram produtos com textura, sabor e aroma mais agradaveis.