Estudo do efeito de cobertura comestível e secagem intermitente sobre a qualidade de manga desidratada
Carregando...
Data
2017-05-26
Autores
Amado, Laís Ravazzi [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
Este trabalho teve como objetivo principal investigar métodos de desidratação de manga em pedaços a partir da combinação de revestimentos comestíveis e secagem intermitente, com o intuito de reduzir o tempo e o consumo energético da operação e melhorar a qualidade do produto desidratado em relação à secagem convencional. Primeiramente buscou-se estudar a intermitência térmica aplicada ao processo de secagem convectiva de fatias de manga (Mangifera indica L.), fruta tropical de elevado conteúdo nutricional e que apresenta ampla aceitação no mercado. A intermitência térmica consistiu em utilizar uma temperatura maior no início da secagem, enquanto a superfície da fruta encontra-se predominantemente saturada, o que fez sua temperatura permanecer baixa devido à intensa evaporação da água. As configurações foram combinações de 95 °C (40 min) e 80 °C (40 min) no primeiro estágio com 70 °C e 60 °C no segundo estágio. O tempo do primeiro estágio foi estabelecido de tal forma que as mangas não ultrapassaram 60 °C durante o período. As secagens controle foram contínuas, a 70 °C e 60 °C. Avaliou-se a influência dessas configurações sobre cinética de secagem, taxas de secagem, consumo energético (calculado através de balanço de entalpia), retenção de cor e de carotenoides. A intermitência aumentou as taxas de secagem, reduzindo o tempo e o consumo energético do processo total. As secagens intermitentes com temperatura de 95 °C no primeiro estágio apresentaram os menores consumos energéticos e valores similares para as temperaturas de 60 °C e de 70 °C aplicadas ao segundo estágio. Os parâmetros de cor não sofreram alterações significativas com as diferentes condições de operação, e o conteúdo de carotenoides foi influenciado positivamente pela intermitência, sendo que a combinação 95 °C/60 °C foi a que melhor protegeu esse nutriente. Posteriormente, foram desenvolvidos filmes comestíveis, que vêm se mostrando promissores em muitas aplicações, visando a melhoria de qualidade de alimentos, tanto pelo efeito protetor quanto pela capacidade de carregar e liberar substâncias de interesse. Formulações de filme à base de proteína isolada de soja (SPI) e pectina de alta metoxilação (PEC) foram selecionadas com base no potencial zeta da solução filmogênica, que indica condições de provável coacervação. Em seguida dois filmes formados apenas por SPI, obtidos no pH 11 e 3, e quatro filmes compostos de SPI e PEC, no pH 3, foram caracterizados por suas propriedades estruturais (FTIR e Raio X) e suas propriedades óticas, mecânicas, solubilidade, morfologia e permeabilidade ao vapor de água e ao oxigênio. Verificou-se que o pH e a concentração de PEC adicionada à solução de SPI influenciaram significativamente a transparência e permeabilidade ao oxigênio dos filmes. O aumento do conteúdo de PEC adicionada não alterou significativamente a solubilidade e a permeabilidade ao vapor de água, porém, elevou a transparência e reduziu a permeabilidade ao oxigênio, inclusive em relação aos filmes formados apenas por SPI. Os filmes comestíveis, os quais têm aplicações diversas foram avaliados, no presente estudo, como coberturas comestíveis. Pedaços de manga foram revestidos com a formulação de menor permeabilidade ao oxigênio, 5% SPI + 2% PEC, e em seguida foram secos até a fruta atingir 9% ± 1% de umidade, através de secagem intermitente em dois estágios (95°C por 40 minutos e segundo estágio à 60°C) e secagem contínua (60°C), condições pré-selecionadas com base na primeira parte da pesquisa. Foi avaliada a influência dessa cobertura comestível e da intermitência térmica sobre a eficiência da secagem e sobre qualidades físicas (cor) e nutricionais (carotenoides e vitamina C) da fruta. Verificou-se que a intermitência térmica aumentou as taxas de secagem das mangas, reduzindo o tempo de operação, além de provocar redução do consumo de energia para o aquecimento do ar e de manter ou até melhorar a qualidade da fruta desidratada em relação às secagens contínuas. Em relação à influência da cobertura, esta não aumentou a resistência à desidratação, e ainda reduziu a degradação de compostos bioativos da manga. Portanto, foi possível comprovar que a aplicação da intermitência térmica e de coberturas comestíveis pode ser bastante eficiente na secagem de mangas.
The main objective of this work was to investigate the methods of drying mango into pieces from the combination of edible coatings and intermittent drying, in order to reduce the time and energy consumption of the operation and to improve the quality of the dried product in relation to the conventional drying. Firstly, we aimed to study the thermal intermittence applied to the convective drying process of mango slices (Mangifera indica L.), a tropical fruit with a high nutritional content and that has wide acceptance in the market. The thermal intermittent consisted of using a higher temperature at the beginning of the drying, while the surface of the fruit is predominantly saturated, which made its temperature remain low due to the intense evaporation of the water. The configurations were combinations of 95 °C (40 min) and 80 °C (40 min) in the first stage with 70 °C and 60 °C in the second stage. The time of the first stage was set in such a way that the sleeves did not exceed 60 °C during the period. Control dryings were continuous at 70 °C and 60 °C. The influence of these configurations on drying kinetics, drying rates, energy consumption (calculated by enthalpy balance), color retention and carotenoids were evaluated. The intermittency increased drying rates, reducing the time and energy consumption of the total process. Intermittent drying at 95 °C in the first stage showed the lowest energy consumption and similar values for the 60 °C and 70 °C temperatures applied to the second stage. The color parameters did not change significantly with the different operating conditions, and the carotenoid content was positively influenced by the intermittence, being that the 95 °C / 60 °C combination was the one that best protected this nutrient. Subsequently, edible films have been developed, which have shown to be promising in many applications aimed at improving food quality, both by the protective effect and by the ability to load and release substances of interest. Formulations of isolated soybean protein (SPI) and high methoxylation pectin (PEC) films were selected based on the zeta potential of the filmogenic solution, which indicates conditions of probable coacervation. In this work, two films formed by SPI, obtained at pH 11 and 3, and four films composed of SPI and PEC at pH 3 were characterized by their structural properties (FTIR and X-ray) and their optical, mechanical, solubility, morphology and permeability to water vapor and oxygen. It was found that the pH and the concentration of PEC added to the SPI solution significantly influenced the transparency and oxygen permeability of the films. The increase of the added PEC content did not significantly alter the solubility and the permeability to water vapor, however, it increased the transparency and reduced the permeability to oxygen, even in relation to the films formed only by SPI. Edible films, which have different applications, were evaluated in the present study as edible coatings. Mango pieces were coated with the formulation of lower oxygen permeability, 5% SPI + 2% PEC, and then dried until the fruit reached 9% ± 1% of moisture, through intermittent drying in two stages (95 ° C for 40 minutes and second stage at 60 ° C) and continuous drying (60 ° C), preselected conditions based on the first part of the research. The influence of this edible coating and the thermal intermittence on the drying efficiency and on the physical (color) and nutritional (carotenoid and vitamin C) qualities of the fruit were evaluated. It was found that the thermal intermittence increased the drying rates, reducing the drying time of the sleeves, as well as reducing energy consumption for air heating and maintain or even improve the quality of the dried fruit in relation to the continuous drying. Regarding the influence of the coating, this did not increase the resistance to drying, and still reduced the degradation of bioactive compounds of the mango. Therefore, it was possible to prove that the application of thermal intermittence and edible coatings can be quite efficient.
The main objective of this work was to investigate the methods of drying mango into pieces from the combination of edible coatings and intermittent drying, in order to reduce the time and energy consumption of the operation and to improve the quality of the dried product in relation to the conventional drying. Firstly, we aimed to study the thermal intermittence applied to the convective drying process of mango slices (Mangifera indica L.), a tropical fruit with a high nutritional content and that has wide acceptance in the market. The thermal intermittent consisted of using a higher temperature at the beginning of the drying, while the surface of the fruit is predominantly saturated, which made its temperature remain low due to the intense evaporation of the water. The configurations were combinations of 95 °C (40 min) and 80 °C (40 min) in the first stage with 70 °C and 60 °C in the second stage. The time of the first stage was set in such a way that the sleeves did not exceed 60 °C during the period. Control dryings were continuous at 70 °C and 60 °C. The influence of these configurations on drying kinetics, drying rates, energy consumption (calculated by enthalpy balance), color retention and carotenoids were evaluated. The intermittency increased drying rates, reducing the time and energy consumption of the total process. Intermittent drying at 95 °C in the first stage showed the lowest energy consumption and similar values for the 60 °C and 70 °C temperatures applied to the second stage. The color parameters did not change significantly with the different operating conditions, and the carotenoid content was positively influenced by the intermittence, being that the 95 °C / 60 °C combination was the one that best protected this nutrient. Subsequently, edible films have been developed, which have shown to be promising in many applications aimed at improving food quality, both by the protective effect and by the ability to load and release substances of interest. Formulations of isolated soybean protein (SPI) and high methoxylation pectin (PEC) films were selected based on the zeta potential of the filmogenic solution, which indicates conditions of probable coacervation. In this work, two films formed by SPI, obtained at pH 11 and 3, and four films composed of SPI and PEC at pH 3 were characterized by their structural properties (FTIR and X-ray) and their optical, mechanical, solubility, morphology and permeability to water vapor and oxygen. It was found that the pH and the concentration of PEC added to the SPI solution significantly influenced the transparency and oxygen permeability of the films. The increase of the added PEC content did not significantly alter the solubility and the permeability to water vapor, however, it increased the transparency and reduced the permeability to oxygen, even in relation to the films formed only by SPI. Edible films, which have different applications, were evaluated in the present study as edible coatings. Mango pieces were coated with the formulation of lower oxygen permeability, 5% SPI + 2% PEC, and then dried until the fruit reached 9% ± 1% of moisture, through intermittent drying in two stages (95 ° C for 40 minutes and second stage at 60 ° C) and continuous drying (60 ° C), preselected conditions based on the first part of the research. The influence of this edible coating and the thermal intermittence on the drying efficiency and on the physical (color) and nutritional (carotenoid and vitamin C) qualities of the fruit were evaluated. It was found that the thermal intermittence increased the drying rates, reducing the drying time of the sleeves, as well as reducing energy consumption for air heating and maintain or even improve the quality of the dried fruit in relation to the continuous drying. Regarding the influence of the coating, this did not increase the resistance to drying, and still reduced the degradation of bioactive compounds of the mango. Therefore, it was possible to prove that the application of thermal intermittence and edible coatings can be quite efficient.
Descrição
Palavras-chave
Mangifera indica L., Secagem convectiva intermitente, Difusão, Filme comestível, Cobertura comestível