611 0195-928X/04/0300-0611/0 © 2004 Plenum Publishing Corporation International Journal of Thermophysics, Vol. 25, No. 2, March 2004 (© 2004) Determination of the Thermal Diffusivity of Edible Films 1 1 Paper presented at the Fifteenth Symposium on Thermophysical Properties, June 22–27, 2003, Boulder, Colorado, U.S.A. S. A. Tomás, 2,3 A. Cruz-Orea, 2 S. Stolik, 4 R. Pedroza-Islas, 5 2 Departamento de Física, CINVESTAV-IPN, AP 14-740, México 07360 D.F., México. 3 To whom correspondence should be addressed. E-mail: stomas@fis.cinvestav.mx 4 Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear, 5ta y 30, No. 502, Miramar, Playa, La Habana, Cuba. 5 Universidad Iberoamericana, Departamento de Ingeniería y Ciencias Químicas, Prol. Reforma 880, Lomas de Santa Fe, México 01210 D.F., México. D. L. Villagómez-Zavala, 5 and C. Gómez-Corona 5 One of the most important factors in the preparation of edible films regards the choice of ingredients. Edible films are commonly prepared with single or mixed high-molecular-weight compounds like proteins and gums. In the present work, protein and gum-based edible films were prepared and their thermal diffusivity determined by photoacoustics. The films were prepared with different concen- trations of four basic ingredients: whey protein concentrate, mesquite gum, sodium alginate, and o-carrageenan. In single-component films, the highest thermal diffusivity was found in mesquite gum (1.97 × 10 -7 m 2 · s -1 ), followed by sodium alginate, whey protein concentrate, and o-carrageenan samples. In composed films, the highest thermal diffusivity was obtained in a ternary film made of mesquite gum, whey protein concentrate, and sodium alginate in iden- tical parts ( 5.20 × 10 -7 m 2 · s -1 ). KEY WORDS: edible films; photoacoustics; thermal diffusivity; whey proteins. 1. INTRODUCTION The development and characterization of edible films have increasingly attracted the attention of biochemists, biotechnologists, and physicists, among others, mainly due to the large variety of applications served by these polymers. Particularly, the capability of edible films to regulate