Emprego de ultrassom de alta intensidade para intensificação da etapa de desidratação osmótica para produção de gengibre semi-desidratado.
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Data
2023-02-17
Autores
Martins, Maria Julia Neves
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
O gengibre é um alimento que vem sendo bastante consumido em várias formulações devido ao seu sabor característico de pungência e pelas propriedades nutracêuticas. Entretanto, sua alta perecibilidade in natura devido à alta umidade é um dos problemas enfrentados pelas indústrias. Por isso, tecnologias combinadas vêm sendo estudadas para melhoria do processo e qualidade do produto final. A desidratação osmótica, aplicada como pré-tratamento à secagem para a redução parcial de umidade, pode ser combinada com aplicação de ultrassom para a intensificação dos processos de transferência de massa. Nestes processos, a sacarose é usada como agente osmótico tradicional, embora venha sendo substituída por glicose, frutose e solutos não convencionais, como o maltitol. Este último permite atender às demandas do consumidor por produtos com teor calórico reduzido. A determinação das propriedades termofísicas das soluções osmóticas em ampla faixa de concentração e temperatura é a etapa inicial necessária para o correto dimensionamento da transferência de massa, assim como outras operações unitárias e dimensionamento de equipamentos. Sendo assim, o objetivo deste estudo foi avaliar a intensificação da etapa de desidratação osmótica de gengibre através do emprego de ultrassom de alta intensidade, visando sua transformação em produto final semi-desidratado. Para isso, inicialmente, soluções osmóticas de sacarose, glicose e frutose foram caracterizadas de acordo com as propriedades termofísicas (densidade, viscosidade, calor específico, condutividade térmica e difusividade térmica) em ampla faixa de concentração (10 a 60°Brix) e temperatura (273,15 a 358,15K). Propriedades de transporte de soluções saturadas convencionais de sacarose e não-convencionais de maltitol também foram estudadas em condições similares de temperatura (273,15 a 358,15K). Foi realizado, então, um estudo comparativo da desidratação osmótica de gengibre em solução saturada de maltitol na condição convencional, agitada mecanicamente (100 rpm) ou assistida por ultrassom de alta intensidade (700W) com sistema pulsado (1 s on; 4 s off) em diferentes temperaturas (25, 35 e 45°C). Como resultados, maiores densidades e menores valores de calor específico e condutividade térmica foram observados para as soluções osmóticas de sacarose, glicose e frutose quando a temperatura diminuiu e a concentração de soluto aumentou. Ao avaliar as soluções saturadas de sacarose e maltitol, a densidade e a difusividade térmica apresentaram valores crescentes com o aumento da temperatura, enquanto o calor específico e a condutividade térmica apresentaram valores decrescentes nas mesmas condições. A viscosidade apresentou comportamento contrário para as soluções com o aumento da temperatura: aumentando para maltitol e diminuindo para sacarose. Tais resultados foram relacionados com as mudanças simultâneas na solubilidade e concentração dos solutos em solução. Por fim, a desidratação osmótica de gengibre em temperaturas mais altas foi intensificada no que diz respeito à perda de água e ganho de sólidos, independente do processo aplicado. Entre as três condições de desidratação osmótica, a condição assistida por ultrassom apresentou maior intensificação de perda de água e ganho de sólidos seguido pela condição agitada mecanicamente e a convencional. O modelo de Weibull apresentou melhores ajustes aos dados experimentais nas três condições de processamento com R2 ≥0,9948 e RMSE ≤0,1158. Portanto, o ultrassom se mostrou como ferramenta eficiente para intensificar a transferência de massa na desidratação osmótica de gengibre com solução saturada de maltitol.
Ginger is a food that has been widely consumed in various formulations due to its characteristic pungent flavor and nutraceutical properties. However, its high perishability in natura due to high moisture is one of the problems faced by industries. Therefore, combined technologies have been studied to improve the process and the quality of the final product. Osmotic dehydration applied as a pre-treatment to drying for partial moisture reduction, can be combined with ultrasound application for the intensification of mass transfer processes. In these processes, sucrose is used as the traditional osmotic agent, although it is being replaced by glucose, fructose, and unconventional solutes such as maltitol. The latter makes it possible to meet consumer demands for low-calorie products. Determining the thermophysical properties of osmotic solutions over a wide concentration and temperature range is a necessary initial step to correctly dimension mass transfer, as well as other unit operations and equipment dimensioning. Thus, the objective of this study was to evaluate the intensification of the ginger osmotic dehydration step through the use of high-intensity ultrasound, aiming its transformation into a semi-dehydrated final product. For this, initially, osmotic solutions of sucrose, glucose, and fructose were characterized according to thermophysical properties (density, viscosity, specific heat, thermal conductivity, and thermal diffusivity) over a wide concentration (10 a 60°Brix) and temperature range (273,15 a 358,15K). Transport properties of conventional saturated sucrose and unconventional maltitol solutions were also studied under similar temperature conditions (273,15 a 358,15K). A comparative study of the osmotic dehydration of ginger in saturated maltitol solution in the conventional condition without stirring, mechanically stirred (100 rpm) or assisted by high-intensity ultrasound (700W) with pulsed system (1 s on; 4 s off) at different temperatures (25, 35 and 45°C) was then performed. As results, higher densities and lower values of specific heat and thermal conductivity were observed for the osmotic solutions of sucrose, glucose and fructose when the temperature decreased and the solute concentration increased. When evaluating the saturated sucrose and maltitol solutions, the density and thermal diffusivity showed increasing values with increasing temperature, while the specific heat and thermal conductivity showed decreasing values under the same conditions. The viscosity showed opposite behavior for the solutions with increasing temperature: increasing for maltitol and decreasing for sucrose. Such results were related to the simultaneous changes in solubility and concentration of the solutes in solution. Finally, osmotic dehydration of ginger at higher temperatures was intensified with respect to water loss and solids gain, regardless of the process applied. Among the three osmotic dehydration conditions, the ultrasound-assisted condition showed the greatest intensification of water loss and solids gain followed by the mechanically agitated and the conventional without agitation condition. The Weibull model showed the better fits to the experimental data in the three processing conditions with R2≥0.9948 and RMSE≤0.1158. Therefore, ultrasound was shown to be an efficient tool to enhance mass transfer in osmotic dehydration of ginger with saturated maltitol solution.
Ginger is a food that has been widely consumed in various formulations due to its characteristic pungent flavor and nutraceutical properties. However, its high perishability in natura due to high moisture is one of the problems faced by industries. Therefore, combined technologies have been studied to improve the process and the quality of the final product. Osmotic dehydration applied as a pre-treatment to drying for partial moisture reduction, can be combined with ultrasound application for the intensification of mass transfer processes. In these processes, sucrose is used as the traditional osmotic agent, although it is being replaced by glucose, fructose, and unconventional solutes such as maltitol. The latter makes it possible to meet consumer demands for low-calorie products. Determining the thermophysical properties of osmotic solutions over a wide concentration and temperature range is a necessary initial step to correctly dimension mass transfer, as well as other unit operations and equipment dimensioning. Thus, the objective of this study was to evaluate the intensification of the ginger osmotic dehydration step through the use of high-intensity ultrasound, aiming its transformation into a semi-dehydrated final product. For this, initially, osmotic solutions of sucrose, glucose, and fructose were characterized according to thermophysical properties (density, viscosity, specific heat, thermal conductivity, and thermal diffusivity) over a wide concentration (10 a 60°Brix) and temperature range (273,15 a 358,15K). Transport properties of conventional saturated sucrose and unconventional maltitol solutions were also studied under similar temperature conditions (273,15 a 358,15K). A comparative study of the osmotic dehydration of ginger in saturated maltitol solution in the conventional condition without stirring, mechanically stirred (100 rpm) or assisted by high-intensity ultrasound (700W) with pulsed system (1 s on; 4 s off) at different temperatures (25, 35 and 45°C) was then performed. As results, higher densities and lower values of specific heat and thermal conductivity were observed for the osmotic solutions of sucrose, glucose and fructose when the temperature decreased and the solute concentration increased. When evaluating the saturated sucrose and maltitol solutions, the density and thermal diffusivity showed increasing values with increasing temperature, while the specific heat and thermal conductivity showed decreasing values under the same conditions. The viscosity showed opposite behavior for the solutions with increasing temperature: increasing for maltitol and decreasing for sucrose. Such results were related to the simultaneous changes in solubility and concentration of the solutes in solution. Finally, osmotic dehydration of ginger at higher temperatures was intensified with respect to water loss and solids gain, regardless of the process applied. Among the three osmotic dehydration conditions, the ultrasound-assisted condition showed the greatest intensification of water loss and solids gain followed by the mechanically agitated and the conventional without agitation condition. The Weibull model showed the better fits to the experimental data in the three processing conditions with R2≥0.9948 and RMSE≤0.1158. Therefore, ultrasound was shown to be an efficient tool to enhance mass transfer in osmotic dehydration of ginger with saturated maltitol solution.
Descrição
Palavras-chave
Sacarose, Glicose, Frutose, Maltitol, Técnicas combinadas, Cavitação, Sucrose, Glucose, Fructose, Combined techniques, Cavitation