Analytical Sciences

Photothermal Techniques Applied to the Determination of the Water Vapor Diffusion Coefficient and Thermal Diffusivity of Edible Films

M. A. AGUILAR-MENDEZ,* E. San MARTIN-MARTINEZ,* J. E. MORALES,** A. CRUZ-OREA,*** and M. R. JAIME-FONSECA*

*Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada del Instituto Politécnico Nacional, Legaria 694, Col. Irrigación, C. P. 11500, México D. F., México
**Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Concepción, Av. Esteban Iturra s/n, Casilla 160-C, Concepción, Chile
***Departamento de Física, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Av. Politécnico 2508, Col. San Pedro Zacatenco, C. P. 07360, México D. F., México

Water vapor diffusion coefficient (WVDC) and thermal diffusivity (α) were determined in gelatin-starch films through photothermal techniques. The effect of different variables in the elaboration of these films, such as starch and glycerol concentrations and pH, were evaluated through the response surface methodology. The results indicated that an increase in the glycerol concentration and pH favored the WVDC of the films. On the other hand, α was influenced principally by the starch content and pH of the film-forming solution. The minimum α value was 4.5 × 10^-4 cm²/s, which is compared with α values reported for commercial synthetic polymers.

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