Estudo da densidade e do comportamento reológico de suco de uva Malbec (Vitis vinifera) em diferentes concentrações e temperaturas
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Data
2020-02-18
Autores
Evangelista, Rodrigo Rodrigues
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
A uva é uma das matérias-primas mais cultivadas em todo o mundo devido à produção de produtos com alto valor agregado, como vinhos e espumantes. Dentre as inúmeras variedades de uvas, destaca-se a uva Malbec (Vitis vinifera), classificada como uva tinta e aplicada na produção de vinhos finos. O presente estudo avaliou a influência da temperatura e concentração no comportamento reológico e da densidade do suco de uva Malbec. As análises foram realizadas em uma ampla faixa de concentração (13,6 a 45,0°Brix), de modo a utilizar o suco de uva concentrado como agente de chaptalização, e também em uma ampla faixa de temperatura (1 a 66°C), que simulam desde condições de armazenamento até a pasteurização do suco. Os parâmetros reológicos, bem como a densidade, foram modelados em função das variáveis temperatura e concentração. As análises reológicas foram realizadas no reômetro rotacional com cilindros concêntricos na taxa de deformação entre 0,84 a 212,1 s-1 e a densidade em um densímetro digital. O suco de uva Malbec foi descrito pelo modelo de Ostwald-de Waele para todas as temperaturas e concentrações analisadas (RAdj2 >0,995 e RQME <1,3), sendo caracterizado como fluido pseudoplástico. Os índices de consistência foram significativamente reduzidos com o aumento da temperatura, seguindo uma relação tipo Arrhenius (RAdj2 >0,983 e RQME <0,14), com energia de ativação variando de 11,02 kJ/mol (45,0°Brix) até 11,54 kJ/mol (21,0°Brix). Em contraste, aumentaram significativamente a concentração, sendo o modelo potencial o que melhor descreveu os dados (RAdj2 >0,999 e RQME <0,11). Por outro lado, os índices de comportamento não apresentaram relação com a temperatura, mas os mesmos reduziram significativamente com o aumento da concentração, sendo descritos pelo modelo potencial (RAdj2 >0,950 e RQME <0,029). No efeito combinado da temperatura e concentração no índice de consistência, o modelo potencial com Arrhenius melhor ajustou-se aos dados apresentando energia única de ativação de 11,11 kJ/mol (RAdj2 = 0,99972 e RQME = 0,083). A viscosidade aparente do suco reduziu e aumentou com o aumento da temperatura e concentração, em uma taxa de deformação fixa, respectivamente. A densidade reduziu e aumentou significativamente com o aumento da temperatura e concentração, respectivamente, sendo descrita pelo modelo polinomial de segunda ordem. O coeficiente de expansão térmica foi determinado para explicar às variações da densidade com a temperatura, indicando que na temperatura de 4,12°C, em qualquer concentração, o suco atingirá sua máxima densidade. Os resultados obtidos podem ser adequados para o potencial uso do suco concentrado como agente de chaptalização na vinificação e instalações industriais para produção de suco e vinho.
The grape is one of the raw materials largely produced worldwide due to its production of high added value products such as wines and sparkling wines. Among the many varieties, it is possible to highlight the Malbec grape (Vitis vinifera) classified as red grape and used for fine wines production. The present study evaluated the influence of temperature and concentration on rheological behavior and density of Malbec grape juice. The analyzes were performed in a wide range of concentration (13.6 to 45.0°Brix), in order to use the concentrates of Malbec as chaptalization agent, and also in a wide range of temperature (1 to 66°C), that simulate storage conditions up to pasteurization process of juice. The rheological parameter, as well the density, were modelling as function of variables temperature and concentration. The rheological analyzes were performed in a rotational rheometer with cylindrical geometric at the shear rate from 0.84 to 212.1 s-1 and the density in a digital densimeter. The Malbec grape juice was described by Ostwald-de Waele model for all temperatures and concentrations analyzed (RAdj2 >0.995 and RSME <1.3), being characterized as shear-thinning fluid type. The consistency coefficients were significantly reduced, following an Arrhenius relationship (RAdj2 >0.983 and RSME <0.14), with activation energy ranging from 11.02 kJ/mol (45.0°Brix) to 11.54 kJ/mol (21.0°Brix). In contrast, they significantly increased the concentration, being the potential model the better described the data (RAdj2 >0.999 e RSME <0.11). In the other hand, the flow behavior index was not influenced by temperature; however, it was closely related with the concentration, being described by potential model (RAdj2 >0.950 e RSME <0.029). In the combined effect of temperature and concentration on the consistency coefficients, the potential with Arrhenius model better fitted to data showing the only activation energy of 11.11 kJ/mol (RAdj2 = 0.99972 and RSME = 0.083). The apparent viscosity of grape juice reduced and increased with the increasing of temperature and concentration, at the same shear rate, respectively. The density reduced and increased significantly with increasing of temperature and concentration, respectively, being describes by second-order polynomial model. The thermal expansion coefficient was determined to explain the changes on density with temperature, indicating at 4.12°C, in any concentration, the juice reach the higher density. The obtained results can be suitable for the potential use of juice concentrate as chaptalization agent in winemaking and industrial facilities for juice and wine production.
The grape is one of the raw materials largely produced worldwide due to its production of high added value products such as wines and sparkling wines. Among the many varieties, it is possible to highlight the Malbec grape (Vitis vinifera) classified as red grape and used for fine wines production. The present study evaluated the influence of temperature and concentration on rheological behavior and density of Malbec grape juice. The analyzes were performed in a wide range of concentration (13.6 to 45.0°Brix), in order to use the concentrates of Malbec as chaptalization agent, and also in a wide range of temperature (1 to 66°C), that simulate storage conditions up to pasteurization process of juice. The rheological parameter, as well the density, were modelling as function of variables temperature and concentration. The rheological analyzes were performed in a rotational rheometer with cylindrical geometric at the shear rate from 0.84 to 212.1 s-1 and the density in a digital densimeter. The Malbec grape juice was described by Ostwald-de Waele model for all temperatures and concentrations analyzed (RAdj2 >0.995 and RSME <1.3), being characterized as shear-thinning fluid type. The consistency coefficients were significantly reduced, following an Arrhenius relationship (RAdj2 >0.983 and RSME <0.14), with activation energy ranging from 11.02 kJ/mol (45.0°Brix) to 11.54 kJ/mol (21.0°Brix). In contrast, they significantly increased the concentration, being the potential model the better described the data (RAdj2 >0.999 e RSME <0.11). In the other hand, the flow behavior index was not influenced by temperature; however, it was closely related with the concentration, being described by potential model (RAdj2 >0.950 e RSME <0.029). In the combined effect of temperature and concentration on the consistency coefficients, the potential with Arrhenius model better fitted to data showing the only activation energy of 11.11 kJ/mol (RAdj2 = 0.99972 and RSME = 0.083). The apparent viscosity of grape juice reduced and increased with the increasing of temperature and concentration, at the same shear rate, respectively. The density reduced and increased significantly with increasing of temperature and concentration, respectively, being describes by second-order polynomial model. The thermal expansion coefficient was determined to explain the changes on density with temperature, indicating at 4.12°C, in any concentration, the juice reach the higher density. The obtained results can be suitable for the potential use of juice concentrate as chaptalization agent in winemaking and industrial facilities for juice and wine production.
Descrição
Palavras-chave
Reologia, Pseudoplástico, Chaptalização, Suco de fruta, Energia de ativação, Rheology, Pseudoplastic, Malbec, Chaptalization, Fruit juice, Activation energy