29E-17 |
Mathematical prediction of cured vanilla beans sorption isotherms |
E. HERMAN-LARA1, M. A. García-Alvarado2, C. E. Martínez-Sánchez1, and C. Lopez-Azamar1. (1) Biochemical Engineering Dept., Instituto Tecnologico de Tuxtepec, Calz. Dr Victor Bravo Ahuja s/n, Col. 5 de Mayo, Tuxtepec, Oax., 68360, Mexico, (2) UNIDA, Instituto Tecnológico de Veracruz, Av. Miguel Angel de Quevedo 2779, P.O. Box 1420, Veracruz, 91860, Mexico Cured vanilla beans from Indian zone in Mexico satisfied physical and chemical parameters of the international norms reported in a previous work except at moisture content. This was probably due to inadequate store and handing conditions of this product. Sorption isotherms of vanilla beans can help to control this parameter. Therefore, the objective of this work was to determinate the experimental sorption isotherms of cured vanilla beans and its mathematical evaluation through empirical and theoretical models at different temperatures. A static gravimetric method was employed for the determination of sorption isotherms of cured vanilla at 35, 40 and 45 oC. Ten saturated salt solutions were prepared corresponding to a range of water activity from about 0.07 to 0.83. In addition, four empirical mathematical expressions taken from the literature were used: Henderson, Mizrahi, Smith and Halsey for fitting the experimental water activity values. Theoretical models of Ross, Norrish and Raoult were included into a computational program BASIC for predicting the water activity values through the chemical composition of cured vanilla beans. Experimental sorption isotherms of vanilla had a similar behavior to the dried products at different temperatures. Predicted sorption isotherms by empirical models established that Henderson equation obtained the best water activity values between 9 and 17 % error except at 45 oC. In addition, chemical composition of vanilla beans was obtained at the laboratory. Solutes like salts and sugars, and non-solutes like fiber were important data for feeding the algorithm into the computational program for predicting the sorption isotherms at any temperature. The estimated results predicted adequately the experimental behavior. Theoretical prediction of sorption isotherms of cured vanilla beans is possible. Time and laboratory work were saved with this method. Therefore vanilla moisture content can be controlled for obtaining a better quality during its storing and handling.
Session 29E, Food Engineering: Transport processes and kinetics
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