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Authors
Abstract(s)
O estudo sobre os parâmetros da secagem é necessário para otimizar o processo e
a obtenção do produto com boa qualidade que satisfaça as exigências dos consumidores.
Assim é necessária a determinação de curvas de secagem, que permitam prever o
momento em que o produto atingirá o teor de água esperado.
No presente trabalho foi efetuada uma caracterização experimental da massa dos
produtos ao longo da secagem, e posteriormente a modelação matemática dos dados
experimentais obtidos. Para este estudo da secagem os produtos utilizados foram os
mirtilos e as framboesas. Estes produtos foram sujeitos a dois tipos de ensaios de
secagem: ao ensaio de secagem completa, em estufa colocada a 105°C para a
determinação da humidade inicial dos produtos e ao ensaio em câmara climática com
controlo das condições de temperatura e da humidade do ar no seu interior. Este processo
foi repetido para todos os casos, tendo por base as condições de temperatura e de
humidade a que se pretendia efetuar a secagem dos produtos. Durante os testes efetuados
na câmara climática foi monitorizada a evolução da massa das amostras ao longo do
tempo de secagem, obtendo-se as respetivas curvas de secagem. As condições de secagem
foram a diferentes temperaturas (40, 50 e 60°C) com humidade relativa de 10%.
Através das curvas de secagem obtidas a partir dos ensaios, observou-se que a
temperatura exerceu grande influência na secagem, pois quando se aumentou a
temperatura ocorreu uma diminuição do tempo do processo e um consequente aumento
da taxa de secagem. Os modelos matemáticos de Newton, o de Henderson e Pabis, o do
Logarítmico e do exponencial de dois termos, foram ajustados aos dados experimentais
mediante uma análise de regressão não-linear, recorrendo ao programa computacional
IMB SPSS STATISTICS. Após a análise matemática, foi verificado que o modelo do
Logarítmico foi o que melhor se ajustou aos dados experimentais com base nos maiores
valores do coeficiente de determinação R² e os menores valores do erro médio absoluto
(MAE) e da raiz do erro quadrático médio (RMSE).
ABSTRACT: The study of drying parameters is necessary to optimize the process and obtain a product with good quality that meets the demands of consumers. So, it is necessary to determine the drying curves, which allow predicting the moment when the product will reach the expected water content. In the present work was done an experimental characterization of the mass of the products during drying, and later the mathematical modeling of the obtained experimental data. For this drying study, the products used were blueberries and raspberries. These products have been subjected to two types of drying tests: the complete drying test, in an oven placed at 105°C for the determination of the initial humidity of the products and the test in a climatic chamber with control of the temperature conditions and humidity inside them. This process was repeated for all cases, based on the temperature and humidity conditions to which the products were to be drying. During the tests in the climate chamber, the evolution of the mass of the samples was monitored over the drying time, obtaining the respective drying curves. Drying conditions were at different temperatures (40, 50 and 60°C) with a relative humidity content of 10%. Through the drying curves obtained from the tests, it was observed that the temperature had a great influence on the drying, because when the temperature was increased, there was a decrease in the process time and a consequent increase in the drying rate. The Newton, Henderson and Pabis, logarithmic and two-term exponential mathematical models, were adjusted to the experimental data through a nonlinear regression analysis, using the computer program IMB SPSS STATISTICS. After the mathematical analysis, it was verified that the Logarithmic model was the best fit to the experimental data based on the highest values of the coefficient of determination R² and the lowest values of the mean absolute error (MAE) and root mean square error (RMSE).
ABSTRACT: The study of drying parameters is necessary to optimize the process and obtain a product with good quality that meets the demands of consumers. So, it is necessary to determine the drying curves, which allow predicting the moment when the product will reach the expected water content. In the present work was done an experimental characterization of the mass of the products during drying, and later the mathematical modeling of the obtained experimental data. For this drying study, the products used were blueberries and raspberries. These products have been subjected to two types of drying tests: the complete drying test, in an oven placed at 105°C for the determination of the initial humidity of the products and the test in a climatic chamber with control of the temperature conditions and humidity inside them. This process was repeated for all cases, based on the temperature and humidity conditions to which the products were to be drying. During the tests in the climate chamber, the evolution of the mass of the samples was monitored over the drying time, obtaining the respective drying curves. Drying conditions were at different temperatures (40, 50 and 60°C) with a relative humidity content of 10%. Through the drying curves obtained from the tests, it was observed that the temperature had a great influence on the drying, because when the temperature was increased, there was a decrease in the process time and a consequent increase in the drying rate. The Newton, Henderson and Pabis, logarithmic and two-term exponential mathematical models, were adjusted to the experimental data through a nonlinear regression analysis, using the computer program IMB SPSS STATISTICS. After the mathematical analysis, it was verified that the Logarithmic model was the best fit to the experimental data based on the highest values of the coefficient of determination R² and the lowest values of the mean absolute error (MAE) and root mean square error (RMSE).
Description
Keywords
Subprodutos Secagem Natural Secagem Artificial Água Teor de Humidade Taxa de secagem Modelos Matemáticos