30F-14 |
Effective diffusivity as selection criteria of wall materials for natural colorant microencapsulation by spray-drying |
C. PÉREZ-ALONSO1, J. G. Báez-González1, C. I. Beristain2, E. J. Vernon-Carter1, and M. G. Vizcarra-Mendoza. (1) IPH, Universidad Autonoma Metropolitana-Iztapalapa, San Rafael Atlixco # 186, Col. La Vicentina, Mexico City, D.F., 09340, Mexico, (2) ICB, Universidad Veracruzana, Luis Castelazo S/N, Col. Industrial-Animas, Xalapa, Ver., 91000, Mexico An adequate protection against environmental factors of encapsulated natural colorants by spray-drying can be achieved by selecting adequately the wall materials. These wall materials must have high emulsifying capacity, low viscosity and retard colorant degradation due to oxidative mechanisms induced by light and oxygen, among other factors. Not one single material complies with all the above mention functionalities, so that it is convenient to use synergism of a blend of materials that may provide these functionalities. The objective of these study was to select beforehand the most appropriate blends of gum arabic (GA) (good emulsifier), mesquite gum (MG) (good protection against degradation by light, good emulsifier) and maltodextrin DE 10 (MD) (good protection against oxidation, bad emulsifier) for encapsulating natural colorants based on the determination of their effective diffusivity and activation energy. The biopolymers were blended in accordance to a simplex centroid experimental design, and were isothermally dried at 50, 60 and 80 °C using thermo gravimetric analysis. Drying curves obtained for all treatments were type 1 (drying rate decreases rapidly as water content decreases)in accordance to Matsuno and Adachi (1993), forming a dense skin immediately upon drying. Effective diffusivity and activation energy were determined using a numerical method (infinite differences) and an analytical method (solving second Fick´s law). Results indicate that the effective diffusivity of the different biopolymer treatments increased as temperature increased. The treatments containing a larger proportion of gum arabic (GA66%-MG17%-MD17%) or mesquite gum (GA17%-MG66%-MD17%) exhibited the largest activation energy, which were comparable to that of maltodextrin on its own. These results imply an adequate selection of biopolymer blends may be achieved through the determination of their effective diffusivities so that they a supply desired set of functionalities.
Session 30F, Food Engineering: Transport processes and kinetics
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