Deise Souza de Castro

Osmotic dehydration kinetics of banana slices considering variable diffusivities and shrinkage

ABSTRACT This article studied the use of diffusion models to describe variation of water quantity and sucrose quantity during osmotic dehydration of bananas cut into cylindrical slices. Bananas with radius of 1.7 cm and 18 °Brix (on average) were cut into 1.0 cm of thickness. A solution was proposed for the diffusion equation in cylindrical coordinates using the finite volume method, with fully implicit formulation. The diffusion equation was discretized assuming diffusivities and dimensions with variable values for the banana slices. Boundary conditions of the third kind have also been considered. The osmotic dehydration experiments were conducted in binary solutions (water and sucrose) under conditions of 40 and 60 °Brix and temperatures of 40 and 70°C. Mathematical modeling was proposed to describe the processes presented good results for water quantity and sucrose quantity, with good statistical indicators for all fits.

Guava Osmotic Dehydration: Description by Two-Dimensional Diffusion Models Considering Shrinkage and Variations in Process Parameters

Abstract This article describes the osmotic dehydration of guava dipped in sucrose solutions using two-dimensional numerical solutions of the diffusion equation with boundary condition of the first kind. Two models are used: model 1 disregards the shrinkage of the product and assumes that effective mass diffusivity does not vary during the process; model 2 takes into account shrinkage, considering effective mass diffusivity as variable. Process parameters estimation is obtained by means of an optimizer. Comparative analyzes indicate that the proposed models have similar statistical indicators. However, model 2 is recommended, for it presents much higher physical fitness when describing mass migrations. Comparison between two-dimensional numerical models presented in this research and one-dimensional models found in the literature reveals that one-dimensional models overestimate process parameters. In addition, one-dimensional models present limitations in predicting the distributions of water and sucrose on guava slices.

Fruit of Mandacaru: Kinetics of Drying and Physical-Chemical Characterization

The drying of the mandacaru fruit consists in an alternative way to reduce loss during its harvest and therefore minimizes its waste. The objective of this study was to physicochemically characterize the mandacaru fruit both fresh and dehydrated in an air circulation oven using three drying temperatures (40, 50 and 60 oC), related to the water content, water activity, pH, acidity and phenolic compounds. Three empirical mathematical models were used to describe the drying (Henderson and Pabis, Midilli and Page). The Midilli’s model had the best statistical indicators, fitting better to the experimental data. The fresh fruit showed water content of 82.75%, water activity of 0.986, titratable acidity of 0.18%, pH of 4.35 and phenolic compounds of 28.35 mg.100-1g. The parameters luminosity (L), intensity of red (+a), yellow intensity (+b), hue angle (ho) and chromaticity (C*) were respectively equal to 59.84±0.08; 5.72±0.06; 89.25±0.08; 5.72±0.06. The physicochemical compounds of the fruit were influenced by the drying, in which water content was 10.83, 8.31 and 7.56%, and the water activity was 3.99. 3.24 and 2.40 for the temperatures of 40, 50 and 60 oC, respectively. The highest temperature caused a greater removal of water in the product along the drying. The dried mandacaru pulp showed titratable acidity of 0.41, 4.86 and 4.98%, pH of 4.76, 4.86 and 4.98 and phenolic compounds of 252.26, 156.53 and 196.10 mg.100-1g, and the parameters L (19.72, 23.41 and 26.15), a* (3.13, 1.31 and 1.30), b* (7.31, 6.53 and 9.14), H* (66.79, 78.69 and 81.92) and C* (7.95, 6.95 and 9.23) at the temperatures of 40, 50 and 60 oC, respectively. The results of the characterization suggest the technological exploitation of the dried mandacaru fruit to add nutritional value to other foods or in the development of new products.

ANÁLISE E DESCRIÇÃO MATEMÁTICA DA SECAGEM DE POLPA DE TATURUBÁ (POUTERIAMACROPHYLLA (LAM.) EYMA.) EM CAMADA FINA

O estudo dos metodos de ampliacao da oferta de frutiferas exotica e desenvolvido de forma a facilitar a industrializacao auxiliando no desenvolvimento de novos produtos. Objetivou-se neste trabalho ajustar modelos matematicos aos dados experimentais de secagem em camada fina de polpa de taturuba ( PouteriaMacrophylla (Lam.) Eyma.) em diferentes temperaturas e determinar a taxa de secagem a partir do melhor modelo representativo do processo. Para a representacao da cinetica de secagem em camada fina foram empregados ajustes dos dados experimentais em diferentes modelos e selecionado aquele que melhor representou o fenomeno de secagem e como criterio de avaliacao destes utilizou-se o coeficiente de determinacao (R 2 ) e o qui-quadrado . Mediante os resultados obtidos observou-se que o aumento da temperatura diminuiu o tempo de secagem da polpa de taturuba. Dentre os modelos aplicados o de Page e o que melhor representa o fenomeno de secagem apresentando os maiores valores de R 2 e os menores valores de X 2 . O tempo do processo variou entre 1550 e 900 minutos. A maxima taxa de secagem obtida por expressao empirica a partir do modelo de Peleg, ocorre no inicio do processo.

INFLUENCE OF TEMPERATURE ON THE PROCESS OF DEHYDRATION OSMOTIC PIECES OF GUAVA

1 Programa de Pós-Graduação em Engenharia Agrícola PPGEA Universidade Federal de Campina Grande – UFCG – Campina Grande/PB Brasil deise_castro01@hotmail.com; jade_nunes@hotmail.com 2 Programa de Pós-Graduação em Engenharia de ProcessosPPGEP Universidade Federal de Campina Grande – UFCG – Campina Grande/PB Brasil aluizio.freire@oi.com.br; juarezeverton@gmail.com 3 Professor Doutor do Departamento de Física Universidade Federal de Campina Grande – UFCG – Campina Grande/PB – Brasil wiltonps@uol.com.br 4 Professora Doutora do Departamento de Engenharia Agrícola Universidade Federal de Campina Grande – UFCG – Campina Grande/PB – Brasil josivanda@gmail.com