Filmes de proteína de soja e carboximetilcelulose e aplicação como cobertura comestível em secagem intermitente de mamão
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Data
2019-08-30
Autores
Oliveira, Maria Mariana Garcia de
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Universidade Estadual Paulista (Unesp)
Resumo
O objetivo do presente trabalho foi investigar a elaboração de coberturas comestíveis à base de proteína e polissacarídeo e suas aplicações em secagem intermitente de mamão em pedaços, a fim de minimizar perdas nutricionais e consumo de energia durante o processo. Filmes à base de proteína isolada de soja (SPI) com adição de diferentes concentrações (0,125; 0,25; 0,375 e 0,5%) de carboximetilcelulose (CMC) foram elaborados em pH 11 e no pH de coacervação (pHc) dos biopolímeros. A intensidade das interações proteínapolissacarídeo, os efeitos do pH, força iônica e razão de SPI/CMC na carga líquida desses biopolímeros foi investigada a partir da medida do potencial zeta das soluções filmogênicas. Os filmes obtidos foram caracterizados quanto a sua morfologia, propriedades mecânicas, estruturais, óticas e permeabilidade ao vapor de água (PVA) e ao oxigênio (PO2). A resistência dos filmes melhorou com o acréscimo crescente do polissacarídeo, porém, filmes em pHc perderam elasticidade, tornando-se mais quebradiços e morfologicamente mais heterogêneos que em pH 11, além de apresentarem grande aumento da opacidade. A PVA dos filmes não apresentou mudanças expressivas com a adição da CMC e/ou mudança no pH, porém, a solubilidade aumentou nos filmes em pH 11. Por outro lado, a permeabilidade ao oxigênio dos filmes em pH 11 diminuiu com a incorporação da CMC na matriz do filme, sendo a formulação composta por 0,375% de CMC a menos permeável ao gás e, portanto, selecionada para aplicação como pré-tratamento na secagem de mamão (Carica papaya L.), na forma de cobertura comestível, com o objetivo de retardar reações oxidativas durante o processo de secagem com ar aquecido Para isso, mamão em pedaços, com ou sem adição de cobertura à sua superfície, foram secos até uma umidade média de 6,67 ± 0,45% (b.u.) por meio de secagem convectiva contínua ou intermitente. Os ensaios de secagem com aplicação de intermitência térmica foram conduzidos em dois estágios, o primeiro com temperaturas elevadas de 80 e 95 °C com duração de 40 e 15 minutos, respectivamente, e, o segundo estágio, à temperatura mais amena de 60 °C. As secagens contínuas foram conduzidas à mesma temperatura do segundo estágio das secagens intermitentes (60 °C). Os efeitos da cobertura e dos diferentes tipos de operação de secagem (com ou sem intermitência) foram avaliados por meio das mudanças nas características físicas e nutricionais do produto final e do consumo energético calculado através de um balanço de energia. Verificou-se que a cobertura melhorou a retenção do licopeno nas secagens contínuas e intermitentes. A aplicação de intermitência térmica, por sua vez, causou maior degradação de licopeno do que as secagens contínuas, independentemente da presença da cobertura. A cor característica do mamão fresco foi conservada ao longo do processo de desidratação e intensificada com a intermitência e a cobertura. Além disso, a aplicação da intermitência térmica reduziu o tempo total do processo, além de proporcionar uma redução de até 17% no consumo energético.
This study aimed to investigate the development of protein and polysaccharide-based edible coatings and its application in intermittent drying of papaya pieces, in order to minimize nutritional losses and energy consuming. Soy protein (SPI) based films with different concentrations (0.125; 0.25; 0.375 and 0.5%) of carboxymethylcellulose (CMC) were prepared at pH 11 and at biopolymers coacervation pH (pHc). The intensity of proteinpolysaccharide interaction, the pH effects, ionic strength and SPI/CMC ratio on the net charge of these biopolymers were investigated by measuring the zeta potential of filmogenic solutions. The films were characterized regarding their morphology, mechanical, structural and optical properties and water vapor (WVP) and oxygen (OP2) permeabilities. The films strength has improved with increasing polysaccharide addition, however, films at pHc lost their elasticity, becoming more brittle and morphologically more heterogeneous than at pH 11, besides presenting a great increase of opacity. The WVP of films didn’t show expressive changes with CMC addition and/or pH change, but they presented increased solubility at pH 11. On the other hand, the oxygen permeability of films at pH 11 decreased with the CMC incorporation in film matrix, being the formulation composed by 0.375% CMC the less permeable to the gas and, therefore, selected to be applied as a pretreatment in papaya (Carica papaya L.) drying, as edible coating, with the goal to delay oxidative reaction during hot air drying. For this, papaya pieces, with or without coating, were dried until to achieve a water content of 6.67 ± 0.45% (w.b.) by continuous or intermittent convective drying. The drying trials with application of thermal intermittence were conducted in two stages. The first one at elevated temperatures of 80 and 95 °C lasting 40 and 15 minutes, respectively, and, the second stage, at lower temperature of 60 °C. The continuous drying was conducted at the same temperature as the second stage of intermittent drying (60 °C). The effects of coating and different drying operations (with and without intermittence) were evaluated by changes in physical and nutritional characteristics of the final product and by the energy consumption calculated through an energy balance. Coating improved the lycopene retention in continuous and intermittent drying. On the other hand, the thermal intermittence caused higher lycopene degradation than continuous drying, regardless the presence of the coating. The fresh papaya characteristic color was preserved throughout the dehydration process and intensified with the intermittence and the coating. Besides that, the thermal intermittence reduced the total drying time and provided an energy saving of approximately 17%.
This study aimed to investigate the development of protein and polysaccharide-based edible coatings and its application in intermittent drying of papaya pieces, in order to minimize nutritional losses and energy consuming. Soy protein (SPI) based films with different concentrations (0.125; 0.25; 0.375 and 0.5%) of carboxymethylcellulose (CMC) were prepared at pH 11 and at biopolymers coacervation pH (pHc). The intensity of proteinpolysaccharide interaction, the pH effects, ionic strength and SPI/CMC ratio on the net charge of these biopolymers were investigated by measuring the zeta potential of filmogenic solutions. The films were characterized regarding their morphology, mechanical, structural and optical properties and water vapor (WVP) and oxygen (OP2) permeabilities. The films strength has improved with increasing polysaccharide addition, however, films at pHc lost their elasticity, becoming more brittle and morphologically more heterogeneous than at pH 11, besides presenting a great increase of opacity. The WVP of films didn’t show expressive changes with CMC addition and/or pH change, but they presented increased solubility at pH 11. On the other hand, the oxygen permeability of films at pH 11 decreased with the CMC incorporation in film matrix, being the formulation composed by 0.375% CMC the less permeable to the gas and, therefore, selected to be applied as a pretreatment in papaya (Carica papaya L.) drying, as edible coating, with the goal to delay oxidative reaction during hot air drying. For this, papaya pieces, with or without coating, were dried until to achieve a water content of 6.67 ± 0.45% (w.b.) by continuous or intermittent convective drying. The drying trials with application of thermal intermittence were conducted in two stages. The first one at elevated temperatures of 80 and 95 °C lasting 40 and 15 minutes, respectively, and, the second stage, at lower temperature of 60 °C. The continuous drying was conducted at the same temperature as the second stage of intermittent drying (60 °C). The effects of coating and different drying operations (with and without intermittence) were evaluated by changes in physical and nutritional characteristics of the final product and by the energy consumption calculated through an energy balance. Coating improved the lycopene retention in continuous and intermittent drying. On the other hand, the thermal intermittence caused higher lycopene degradation than continuous drying, regardless the presence of the coating. The fresh papaya characteristic color was preserved throughout the dehydration process and intensified with the intermittence and the coating. Besides that, the thermal intermittence reduced the total drying time and provided an energy saving of approximately 17%.
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Palavras-chave
Filmes biodegradáveis, Cobertura comestível, Secagem convectiva, Intermitência térmica, Consumo energético, Carotenoides, Biodegradable films, Edible coating, Convective drying, Thermal intermittence, Energy consumption, Carotenoids