Reidratação e comportamento reológico de cranberries desidratadas
Dried cranberries are fruits that have been submitted to drying process and are known for their high antioxidant potential. In North America, they are traditionally consumed as additives in breakfast cereals, yogurts and pasta. Changes in mechanical and rheological properties occur when cranberries...
| Autor principal: | Ciolin, Ígor Henrique de Mello Rodrigues |
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| Formato: | Trabalho de Conclusão de Curso (Graduação) |
| Idioma: | Português |
| Publicado em: |
Universidade Tecnológica Federal do Paraná
2020
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| Assuntos: | |
| Acesso em linha: |
http://repositorio.utfpr.edu.br/jspui/handle/1/12634 |
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| Resumo: |
Dried cranberries are fruits that have been submitted to drying process and are known for their high antioxidant potential. In North America, they are traditionally consumed as additives in breakfast cereals, yogurts and pasta. Changes in mechanical and rheological properties occur when cranberries are exposed to conditions such as drying, or when immersed in aqueous medium. This work aimed to study the physicochemical characterization of dried cranberries, the kinetics modelling of cranberries rehydration at different temperatures and immersion media, the texture profile analysis of dried and rehydrated cranberries and determination of rheological behavior of cranberries suspension at different solid concentrations and different temperatures. The fruits were rehydrated in water and in milk for 6 h at temperatures of 10, 29 (room temperature) and 45°C, the sample weights were recorded periodically. Twelve models were used to describe the kinetics of the fruit rehydration, as the Fick’s second law satisfactorily represented the experimental data (R2 > 0,92). The diffusion coefficients of water and milk during the cranberries rehydration ranged from 8,33∙10-5 to 1,50∙10-4 cm² s-1. For the cranberries rehydrated in water at 10 ºC the Page model was the best fit to the experimental data (R² = 0,98), at 29 ºC, the model of diffusion approximation (R² = 0,98) and at 45 ºC, the Verma model (R² = 0,99). Considering texture, the cohesiveness of rehydrated fruits showed a significant reduction when compared to the cohesiveness of dried fruits. In order to evaluate the rheological behavior of solid suspensions, it was used five different models (Ostwald de Waelle, Newton, Herschel Bulkley, Casson e Bingham), and the rheological behavior of suspensions was defined as Casson’s plastic, since the model showed a satisfactory fit to all temperatures and concentrations analyzed, with (R² > 0,94), low values of P and RMSE and ideal values of Bf. Also, it was analyzed the effects of independent variables measurement temperature and concentration of suspended solids (dried cranberries) on the Casson initial shearing tension results (K0C) and Casson plastic viscosity (KC). It was found that the increase of suspension concentration above 20%, increased the initial shearing tension, this parameter is affected by the temperature, once an increase of temperature decreases significantly the results when using concentration of 30%. Considering plastic viscosity (Kc), the concentration of solids was the key parameter to determine (KC) and, consequently, the apparent viscosity. Also, higher temperatures decreased values of (KC), once its greatest value was obtained at concentrations above 20% and low temperatures. |
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