Efeito da temperatura e graus plato no comportamento reológico do mosto de cerveja lupulado tipo lager
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2020-09-04
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Universidade Estadual Paulista (Unesp)
Resumo
A viscosidade é uma propriedade física de amplo interesse, pois é um fator fundamental para cálculos que envolvem a seleção e dimensionamento de equipamentos. Este trabalho aborda a produção do mosto cervejeiro tipo lager, produto obtido da mistura do malte de cevada e adjunto de malte (grits de milho), em água tratada, na proporção de 65/35 (malte/adjunto). A obtenção do mosto consistiu nos processos de mosturação, filtração, fervura e resfriamento. Além disso, o comportamento reológico foi determinado nas temperaturas de 1 a 95 °C, concentrações de 1 a 27 °P e taxa de deformação variando entre 1,057 a 263,673 s–1. Para estudar o efeito da temperatura e concentração no comportamento reológico, fez-se o uso de um reômetro rotacional de cilindros concêntricos, os ensaios ocorreram em triplicatas, no laboratório de propriedades físicas da Unesp no campus de São José do Rio Preto. O modelo de Oswald-de-Waale foi ajustado aos dados experimentais, sendo este avaliado, pelo coeficiente de determinação (R²) e Erro Médio Relativo, no programa OriginPro 8.0. Análises de variância (ANOVA) foram efetuadas para verificar se a viscosidade variou significativamente com a temperatura para uma determinada concentração (α = 0,01), no software Minitab 17. A relação entre temperatura e viscosidade foi descrita por uma equação tipo Arrhenius e o efeito entre concentração e viscosidade pelo modelo da potência e exponencial. Além disso, foi proposto o modelo combinado em função da temperatura e concentração para descrever o comportamento reológico. Pode-se concluir que o mosto cervejeiro se comportou como um fluido newtoniano em todas as temperaturas e concentrações, pois o índice de comportamento se apresentou igual a unidade com R² > 0,999 ± 0,0001. O aumento da temperatura reduziu significativamente a viscosidade (p < 0,05), apresentando valores de energia de ativação entre 9,633 ± 0,318 a 15,349 ± 0,273 KJ/mol, com R² superior a 0,982 ± 0,003. A concentração demonstrou correlação positiva com a viscosidade e, o modelo exponencial apresentou o melhor ajuste com R² > 0,9377. Esta dependência pode ser observada no modelo combinado em função da temperatura (𝑇��) em [𝐾��] e concentração (𝐶��) em [°𝑃��], resultando na viscosidade absoluta (𝜇��𝑎��𝑏��) em [Pa.s], com R² > 0,961 ± 0,001.
Viscosity is a physical property of wide interest, as it is a fundamental factor for calculations involving the selection and dimensioning of equipment. This work deals with the production of lager hopped wort, a substance obtained from the mixture of barley malt and malt adjunct (corn grits), in treated water, in the proportion of 65/35 (malt/adjunct). The obtaining of the wort consisted of the processes of mashing, filtration, boiling and cooling. In addition, the rheological behavior was determined at temperatures from 1 to 95°C, concentrations from 1 to 27°P and strain rate varying between 1.057 to 263.673 s–1. In order to study the effect of temperature and concentration on rheological behavior, a rotational concentric cylinder rheometer was used, the tests are carried out in triplicates. The experimental data were adjusted in the Oswald-de-Waale model, which was evaluated by the coefficient of determination (R²) and Relative Mean Error, in the OriginPro 8.0 softwares. Analysis of variance (ANOVA) was performed to verify whether the viscosity varied significantly with temperature for a given concentration (α < 0.01), in the Minitab 17 software. The relationship between temperature and viscosity was described by an Arrhenius equation and the effect between concentration and viscosity by the power and exponential model. In addition, a combined model of temperature and concentration was proposed to describe the rheological behavior. It can be concluded that the hopped wort behaved like a Newtonian fluid at all temperatures and concentrations, presenting (R² > 0.999 ± 0.0001). The increase in temperature significantly reduced the viscosity (p < 0.05), with activation energy values between 9.633 ± 0.318 to 15.349 ± 0.273 KJ/mol, R² > 0,982 ± 0,003. The concentration showed a positive correlation with viscosity and the exponential model demonstrated the best fit with R² > 0.9377. This dependence can be seen in the combined model, of the temperature (T) in [K] and concentration (C) in [°P], resulting in the absolute viscosity (𝜇�𝑎�𝑏�) em [Pa.s], R² > 0,961 ± 0,001.
Viscosity is a physical property of wide interest, as it is a fundamental factor for calculations involving the selection and dimensioning of equipment. This work deals with the production of lager hopped wort, a substance obtained from the mixture of barley malt and malt adjunct (corn grits), in treated water, in the proportion of 65/35 (malt/adjunct). The obtaining of the wort consisted of the processes of mashing, filtration, boiling and cooling. In addition, the rheological behavior was determined at temperatures from 1 to 95°C, concentrations from 1 to 27°P and strain rate varying between 1.057 to 263.673 s–1. In order to study the effect of temperature and concentration on rheological behavior, a rotational concentric cylinder rheometer was used, the tests are carried out in triplicates. The experimental data were adjusted in the Oswald-de-Waale model, which was evaluated by the coefficient of determination (R²) and Relative Mean Error, in the OriginPro 8.0 softwares. Analysis of variance (ANOVA) was performed to verify whether the viscosity varied significantly with temperature for a given concentration (α < 0.01), in the Minitab 17 software. The relationship between temperature and viscosity was described by an Arrhenius equation and the effect between concentration and viscosity by the power and exponential model. In addition, a combined model of temperature and concentration was proposed to describe the rheological behavior. It can be concluded that the hopped wort behaved like a Newtonian fluid at all temperatures and concentrations, presenting (R² > 0.999 ± 0.0001). The increase in temperature significantly reduced the viscosity (p < 0.05), with activation energy values between 9.633 ± 0.318 to 15.349 ± 0.273 KJ/mol, R² > 0,982 ± 0,003. The concentration showed a positive correlation with viscosity and the exponential model demonstrated the best fit with R² > 0.9377. This dependence can be seen in the combined model, of the temperature (T) in [K] and concentration (C) in [°P], resulting in the absolute viscosity (𝜇�𝑎�𝑏�) em [Pa.s], R² > 0,961 ± 0,001.
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Mosto lupulado, Viscosidade mosto lager, Viscosidade mosto lupulado, Reologia, Liquido newtoniano, Hopped wort, Wort lager viscosity, Hopped wort viscosity, Rheology, Newtonian liquid