Liofilização de fatias de abacaxi: avaliação da cinética de secagem e da qualidade do produto
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Data
2012-03-01
Autores
Vieira, Ana Paula [UNESP]
Nicoleti, Joel Fernando
Telis, Vânia Regina Nicoletti [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Instituto de Tecnologia de Alimentos - ITAL
Resumo
O objetivo deste trabalho foi avaliar a cinética de secagem e os parâmetros de qualidade - conteúdo de vitamina C, reidratação e textura - de fatias de abacaxi liofilizadas em função da espessura e da temperatura de congelamento. Abacaxis do tipo Havaí, variedade Smooth Cayenne, foram fatiados transversalmente em espessuras de 0,5, 1,0 e 1,5 cm. As fatias foram congeladas nas temperaturas de -14, -24 e -34 °C, sendo, em seguida, conduzidas ao liofilizador. Uma parcela das amostras era destinada ao estudo da cinética de secagem pela pesagem periódica das mesmas, enquanto outra foi reservada para os testes de qualidade. O teor de vitamina C foi quantificado por adição de ácido oxálico na amostra e titulado com 2,6-diclorofenolindofenol. O parâmetro de textura avaliado foi a dureza, por testes de compressão em texturômetro, enquanto a reidratação foi obtida pela pesagem das amostras antes e após a imersão em água destilada por 5 min. Os resultados do presente trabalho mostraram que existe uma forte dependência da cinética de secagem e dos atributos de qualidade de fatias de abacaxi liofilizadas em função das condições utilizadas durante a etapa de congelamento, mesmo sendo este classificado como congelamento lento. Por outro lado, a taxa de congelamento não é a única variável que tem influência sobre a cinética de secagem e os atributos de qualidade. A combinação de temperatura e umidade, tanto durante a liofilização propriamente dita, quanto durante a etapa de reidratação, tem influência sobre a transição vítrea do material que, por sua vez, afeta a extensão do colapso estrutural sofrido pelo produto.
The aim of this study was to evaluate the drying kinetics and quality parameters - vitamin C content, rehydration and texture - of freeze dried pineapple slices, according to the thickness and temperature of freezing. Pineapples of the Hawaii type, Smooth Cayenne variety, were sliced transversely with thicknesses of 0.5, 1.0 and 1.5 cm. The slices were frozen at temperatures of -14, -24 and -34 °C, and then freeze dried. One part of the samples was used to study the drying kinetics by periodic weighing, while the other was reserved for the quality tests. The vitamin C content was quantified by adding oxalic acid to the sample and titrating with 2,6-dichlorophenolindophenol. The texture parameter evaluated was that of hardness, evaluated by compression tests in a texturometer, while rehydration was determined by weighing the samples before and after immersion in water for 5 min. The results of this study showed there was a strong dependence of the drying kinetics and quality attributes of the dried pineapple slices on the conditions used during the freezing step, even though this was classified as slow freezing. Nevertheless the freezing rate was not the only variable that influenced the drying kinetics and quality attributes. The combination of temperature and humidity, both during the freeze drying process itself, and also during the rehydration step, influences the glass transition of the material which, in turn, affects the extent of structural collapse suffered by the product.
The aim of this study was to evaluate the drying kinetics and quality parameters - vitamin C content, rehydration and texture - of freeze dried pineapple slices, according to the thickness and temperature of freezing. Pineapples of the Hawaii type, Smooth Cayenne variety, were sliced transversely with thicknesses of 0.5, 1.0 and 1.5 cm. The slices were frozen at temperatures of -14, -24 and -34 °C, and then freeze dried. One part of the samples was used to study the drying kinetics by periodic weighing, while the other was reserved for the quality tests. The vitamin C content was quantified by adding oxalic acid to the sample and titrating with 2,6-dichlorophenolindophenol. The texture parameter evaluated was that of hardness, evaluated by compression tests in a texturometer, while rehydration was determined by weighing the samples before and after immersion in water for 5 min. The results of this study showed there was a strong dependence of the drying kinetics and quality attributes of the dried pineapple slices on the conditions used during the freezing step, even though this was classified as slow freezing. Nevertheless the freezing rate was not the only variable that influenced the drying kinetics and quality attributes. The combination of temperature and humidity, both during the freeze drying process itself, and also during the rehydration step, influences the glass transition of the material which, in turn, affects the extent of structural collapse suffered by the product.
Descrição
Palavras-chave
Abacaxi, Liofilização, Cinética, Qualidade, Pineapples, Freeze drying, Kinetics, Quality
Como citar
Brazilian Journal of Food Technology. Instituto de Tecnologia de Alimentos - ITAL, v. 15, n. 1, p. 50-58, 2012.