Estudo da cinética de secagem de pimenta malagueta (Capsicum frutescens) e influência da temperatura no teor de capsaicina
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Data
2016-07-01
Autores
Catelam, Kelly Tafari [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
De maneira geral, a diversidade e a pungência dos frutos de pimenta, seus atributos sensoriais, a composição química, as ações fisiológicas correlatas e o crescimento da aceitação e da preferência por várias populações, aumentaram o interesse na pesquisa científica relacionada com os diferentes aspectos desta cultura. Apesar de ser abundantemente encontrada em todo o país, há pouca informação científica sobre a pimenta malagueta. Neste estudo, determinou-se a cinética de secagem da pimenta malagueta (Capsicum frutescens) a 40, 50, 60 e 70°C por meio da secagem em secador de leito fixo por 5 horas, aplicando-se os modelos empíricos de Page, Henderson-Pabis e Lewis. Observou-se maior rapidez na queda de umidade (aumento da taxa de secagem) com o aumento da temperatura de secagem. Todas as taxas de secagem obtidas foram decrescentes, não sendo observado período de taxa constante de secagem, indicando, assim, que o principal mecanismo de migração da água do interior do produto para sua superfície é a difusão. O modelo que melhor se ajustou aos dados foi o de Page. Calculou-se o coeficiente de difusão da pimenta utilizando a solução analítica da segunda lei de Fick para geometria de cilindro finito, observando-se um aumento da difusividade com a temperatura. Avaliou-se o teor de capsaicina na pimenta in natura e após a secagem nas 4 temperaturas estudadas por cromatografia líquida de alta eficiência, observando-se que não houve diferença significativa entre os tratamentos quanto ao teor de capsaicina. Construíram-se as isotermas de adsorção a 40, 50, 60 e 70°C das pimentas desidratadas a 40, 50, 60 e 70°C em secador de leito fixo e verificou-se qual o melhor modelo matemático que se ajustava aos dados experimentais. A partir do melhor modelo (modelo de GAB), determinaram-se as propriedades termodinâmicas de sorção da água (calor isostérico de sorção, entropia diferencial e energia livre de Gibbs) da pimenta malagueta seca, através dos dados fornecidos das isotermas de adsorção deste material. Pelos resultados, tem-se que os melhores modelos ajustados às isotermas foram os de GAB e Kaleemullah, sendo que o primeiro foi usado para o cálculo das propriedades termodinâmicas. O calor isostérico diminuiu com o aumento da umidade de equilíbrio, enquanto a variação de energia livre de Gibbs mostrou um incremento com o aumento da umidade de equilíbrio para todos os níveis de temperatura, estando todos os valores abaixo de zero. Observou-se uma queda da variação de entropia diferencial com o conteúdo de umidade de equilíbrio. Pela relação entalpia-entropia, notou-se um aumento da entalpia em função do incremento na entropia. A temperatura isocinética foi maior que a temperatura harmônica, mostrando que o processo é controlado pela entalpia.
In general, the diversity and the pungency of chili peppers fruits, their sensory attributes, chemical composition, related physiological actions and the growing acceptance and preference for various populations, increased interest in scientific research related to the different aspects of this culture. Despite being abundantly found across the country, there is little scientific information about the malagueta chili pepper. In this study, the drying kinetics of malagueta chili peppers (Capsicum frutescens) were determined at 40, 50, 60 and 70ºC in a fixed bed dryer, drying for 5 hours, by applying the empirical models of Page, Henderson-Pabis and Lewis. It was shown that the moisture content fell quicker (increase in the drying rate) the higher the drying temperature. All the drying rates obtained were decreasing, no constant drying rate being observed, indicating that the main mechanism for migration of the water from the interior to the surface of the product was diffusion. The Page model fitted the data best. The coefficient of diffusion of the peppers was calculated using the analytical solution of Fick’s second law for a finite cylindrical geometry, observing an increase in diffusivity with temperature. The capsaicin content of the peppers was determined by high performance liquid chromatography in the in natura peppers and after drying by four temperatures evaluated, and no significant differences between the treatments were found. Isotherms were constructed for the adsorption of water at 40, 50, 60, and 70°C by chili peppers dehydrated at 40, 50, 60 and 70°C in a fixed-bed dryer, and to identify the best mathematical model for fitting the experimental data. The selected model was then used to determine the thermodynamic properties of water sorption for dry chili pepper (isosteric heat of sorption, differential entropy, and Gibbs free energy) using data obtained from the adsorption isotherms. The results showed that the best fits to the isotherms were obtained using the GAB and Kaleemullah models, and the former was used to calculate the thermodynamic properties. The isosteric heat of sorption decreased with increasing equilibrium moisture content, while Gibbs free energy increased at higher equilibrium moisture content, for all temperatures, with all values being below zero. The differential entropy decreased with the equilibrium moisture content. The enthalpy-entropy ratio showed that the enthalpy increased as a function of the increase in entropy. The isokinetic temperature was higher than the harmonic temperature, demonstrating that the process was controlled by the enthalpy.
In general, the diversity and the pungency of chili peppers fruits, their sensory attributes, chemical composition, related physiological actions and the growing acceptance and preference for various populations, increased interest in scientific research related to the different aspects of this culture. Despite being abundantly found across the country, there is little scientific information about the malagueta chili pepper. In this study, the drying kinetics of malagueta chili peppers (Capsicum frutescens) were determined at 40, 50, 60 and 70ºC in a fixed bed dryer, drying for 5 hours, by applying the empirical models of Page, Henderson-Pabis and Lewis. It was shown that the moisture content fell quicker (increase in the drying rate) the higher the drying temperature. All the drying rates obtained were decreasing, no constant drying rate being observed, indicating that the main mechanism for migration of the water from the interior to the surface of the product was diffusion. The Page model fitted the data best. The coefficient of diffusion of the peppers was calculated using the analytical solution of Fick’s second law for a finite cylindrical geometry, observing an increase in diffusivity with temperature. The capsaicin content of the peppers was determined by high performance liquid chromatography in the in natura peppers and after drying by four temperatures evaluated, and no significant differences between the treatments were found. Isotherms were constructed for the adsorption of water at 40, 50, 60, and 70°C by chili peppers dehydrated at 40, 50, 60 and 70°C in a fixed-bed dryer, and to identify the best mathematical model for fitting the experimental data. The selected model was then used to determine the thermodynamic properties of water sorption for dry chili pepper (isosteric heat of sorption, differential entropy, and Gibbs free energy) using data obtained from the adsorption isotherms. The results showed that the best fits to the isotherms were obtained using the GAB and Kaleemullah models, and the former was used to calculate the thermodynamic properties. The isosteric heat of sorption decreased with increasing equilibrium moisture content, while Gibbs free energy increased at higher equilibrium moisture content, for all temperatures, with all values being below zero. The differential entropy decreased with the equilibrium moisture content. The enthalpy-entropy ratio showed that the enthalpy increased as a function of the increase in entropy. The isokinetic temperature was higher than the harmonic temperature, demonstrating that the process was controlled by the enthalpy.
Descrição
Palavras-chave
Difusividade, HPLC, Isotermas, GAB, Calor líquido isostérico de sorção, Entropia diferencial, Energia livre de Gibbs, Diffusivity, HPLC, Isotherms, GAB, Net isosteric heat of sorption, Differential entropy, Gibbs free energy