Estudo da secagem do kiwi com pré-tratamento osmótico e seu efeito no teor de macro e micronutrientes do fruto
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Data
2017-03-30
Autores
Rocha, Luzimary de Jesus Ferreira Godinho [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
O armazenamento de alimentos envolve etapas que variam das mais simples às mais complexas. Dentre elas, destaca-se a desidratação osmótica e secagem convectiva, garantindo a manutenção dos nutrientes a um baixo custo. Na etapa de desidratação osmótica, ocorre adição de solutos que indisponibilizam parte da água do alimento reduzindo atividade biológica e algumas reações mantendo estrutura desejável do produto. Na secagem convectiva reduz-se o a atividade da água no produto. O consumo de frutas exóticas no Brasil cresceu muito nos últimos anos, despertando o interesse de grandes empresas e agências de pesquisas. O kiwi está entre essas frutas apresentando paladar agradável ao consumidor brasileiro, que têm demonstrado grande interesse nesse fruto. Já existe no país, lugares de cultivo com grandes chances de boas colheitas. Os objetivos do presente estudo foram a obtenção de parâmetros da cinética de secagem, a modelagem matemática e a determinação de características físico-químicas e do efeito do processo no teor de macro e micronutrientes do fruto para efeito de preparo do kiwi desidratado com possibilidade de comercialização. São apresentados resultados de experimentos de secagem do kiwi descascado e fatiado com espessura de cerca de 7 mm, pré-tratado em solução osmótica de sacarose e seco em um secador de leito fixo. Os testes foram feitos em quatro temperaturas de 40°C, 50°C, 60°C e 70 °C com ± 3°C e velocidade do ar de 2,1 m·s-1. Os modelos empíricos de Page, Page Modificado, Peleg, Henderson-Pabis, Henderson-Pabis modificado, Newton e o modelo teórico difusivo foram empregados na modelagem das cinéticas de secagem. Na análise gráfica foi encontrado um período de taxa decrescente durante a secagem. Todos os modelos apresentaram bons ajustes aos dados de umidade versus tempo de secagem. Através da técnica de Espectrometria de Emissão Atômica por Plasma Acoplado Indutivamente, determinaram-se os teores dos seguintes minerais com as amostras de kiwi antes e após a desidratação osmótica: alumínio, cálcio, cobre, fósforo, manganês, magnésio, potássio, sódio e zinco, observando-se o aumento da concentração de fósforo, magnésio e potássio com pré-tratamento osmótico.
Food storage involves steps that range from the simplest to the most complex. Among them, the osmotic dehydration and convective drying stand out, guaranteeing the maintenance of the nutrients at a low cost. In the stage of osmotic dehydration, there is addition of solutes that unavailable part of the water of the food reducing biological activity and some reactions maintaining a desirable structure of the product. Convective drying reduces the water activity in the product. The consumption of exotic fruits in Brazil has grown a lot in the last years, arousing the interest of big companies and research agencies. The kiwifruit is among these fruits presenting pleasant taste to the Brazilian consumer, who have shown great interest in this fruit. There already exists in the country, places of cultivation with great chances of good harvests. The objectives of the present study were to obtain parameters of drying kinetics, mathematical modeling and the determination of physico-chemical characteristics and the effect of the process on the macro and micronutrients content of the fruit for the purpose of preparing the dehydrated kiwi with the possibility of commercialization. Results of drying experiments of the peeled and sliced kiwifruit are presented with thickness of about 7 mm, pretreated in sucrose osmotic solution and dried in a fixed bed drier. The tests were done at four temperatures of 40°C, 50°C, 60°C and 70°C with ± 3°C and air velocity of 2.1 m.s-1. The empirical models of Page, Page Modified, Peleg, Henderson-Pabis, Henderson-Pabis modified, Newton and the theoretical diffusive model were used in the modeling of drying kinetics. In the graphical analysis was found a period of decreasing rate during the drying. All models presented good adjustments to the moisture data versus drying time. The levels of the following minerals by Inductively Coupled Plasma Atomic Emission Spectrometry were determined with kiwifruit samples before and after osmotic dehydration: aluminum, calcium, copper, iron, phosphorus, manganese, magnesium, potassium, sodium and zinc, observing increased phosphorus, magnesium and potassium concentration with osmotic pretreatment.
Food storage involves steps that range from the simplest to the most complex. Among them, the osmotic dehydration and convective drying stand out, guaranteeing the maintenance of the nutrients at a low cost. In the stage of osmotic dehydration, there is addition of solutes that unavailable part of the water of the food reducing biological activity and some reactions maintaining a desirable structure of the product. Convective drying reduces the water activity in the product. The consumption of exotic fruits in Brazil has grown a lot in the last years, arousing the interest of big companies and research agencies. The kiwifruit is among these fruits presenting pleasant taste to the Brazilian consumer, who have shown great interest in this fruit. There already exists in the country, places of cultivation with great chances of good harvests. The objectives of the present study were to obtain parameters of drying kinetics, mathematical modeling and the determination of physico-chemical characteristics and the effect of the process on the macro and micronutrients content of the fruit for the purpose of preparing the dehydrated kiwi with the possibility of commercialization. Results of drying experiments of the peeled and sliced kiwifruit are presented with thickness of about 7 mm, pretreated in sucrose osmotic solution and dried in a fixed bed drier. The tests were done at four temperatures of 40°C, 50°C, 60°C and 70°C with ± 3°C and air velocity of 2.1 m.s-1. The empirical models of Page, Page Modified, Peleg, Henderson-Pabis, Henderson-Pabis modified, Newton and the theoretical diffusive model were used in the modeling of drying kinetics. In the graphical analysis was found a period of decreasing rate during the drying. All models presented good adjustments to the moisture data versus drying time. The levels of the following minerals by Inductively Coupled Plasma Atomic Emission Spectrometry were determined with kiwifruit samples before and after osmotic dehydration: aluminum, calcium, copper, iron, phosphorus, manganese, magnesium, potassium, sodium and zinc, observing increased phosphorus, magnesium and potassium concentration with osmotic pretreatment.
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Palavras-chave
Kiwi, Secagem, Modelos matemáticos, Minerais, Kiwifruit, Drying, Mathematicals models, Minerals