30F-15 |
Effective diffusivity of biopolymers solutions using regular regime method coupled with image analysis |
J. G. BÁEZ-GONZÁLEZ1, C. Pérez-Alonso1, C. I. Beristain2, E. J. Vernon-Carter1, and M. G. Vizcarra-Mendoza1. (1) IPH, Universidad Autonoma Metropolitana-Iztapalapa, San Rafael Atlixco # 186, Col. La Vicentina, Mexico City, D.F., 09340, Mexico, (2) IPH, Universidad Veracruzana, Luis Castelazo S/N, Col. Industrial-Animas, Xalapa, Ver., 91000, Mexico Several methods have been proposed for assessing the properties of wall materials for use in a specific encapsulation procedure. For the spray-drying technique it is convenient that wall materials form dense fine matrixes immediately upon drying, so the rate of moisture removal is governed by diffusion. Determination of the effective diffusivity of moisture in biopolymers aqueous solutions has been done using the Regular Regime Method. During the drying process two distinctive zones exist: 1) induction period in which the initial moisture content is important (constant drying period), and 2) the regular regime period where the initial moisture content is not important (decreasing drying period). The interval of moisture content in the regular regime is used in calculating the effective diffusion. The objective of this work was to develop an experimental procedure for obtaining isothermal drying curves at different temperatures of biopolymer aqueous solutions, and to determine their effective diffusivities considering their experimental shrinkage, using the Regular Regime Method. Isothermal drying curves were obtained using a thermo-gravimetric analyzer. Experimental shrinkage of the biopolymers upon drying was measured with an image analyzer, and the functionality between moisture content and volume change was established, and introduced into the Regular Regime Method to compute effective diffusivities. The results obtained show that diffusivity is highly dependent on moisture content, shrinkage (characteristic shrinkage of biopolymers was around 30-40% of initial volume), and temperature. Diffusion – moisture content curves were obtained for each biopolymer studied. It is hoped that the experimental procedure presented here will contribute to determine with greater precision the effective diffusivities of biopolymers, so that this parameter may be used as a discriminative screen for selecting these materials for specific food science and technology applications.
Session 30F, Food Engineering: Transport processes and kinetics
|