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Effect of Xanthan Gum and CMC on the Structure and Texture of Corn Flour Pellets Expanded by Microwave Heating

¹Center for Advanced Food Technology and Department of Food Science, Rutgers—The State University of New Jersey, 65 Dudley Road, New Brunswick, NJ 08901. ²Currently with the Department of Food Science, Cornell University, Ithaca, NY 14850. ³Corresponding author. Phone: 732-932-9611, ext.201. E-mail: kokini@aesop.rutgers.edu

Third-generation snacks obtained by microwave expansion of glassy cereal pellets are often hard and nonuniform and need to be improved to become acceptable to the consumer. Gums such as carboxymethyl cellulose (CMC) and xanthan gum (XG) have the ability to improve the volume, structure, and texture of expanded cereal products, due to their effects on moisture retention and rheological properties. This study investigates the effect of 1% addition of CMC and XG on the structural and mechanical properties of samples obtained by microwave expansion of glassy corn pellets. Unexpanded, glassy pellets were obtained by extrusion and subsequent equilibration at a_w = 0.53 at room temperature. The equilibrated pellets were expanded by microwave heating. The addition of gums significantly improved the shape, structural and textural uniformity of the microwave-expanded samples. These effects were attributed to the contribution of gums to the rheology and moisture sorption capacity of the matrix. It is our hypothesis that the extended hydrocolloid macromolecules interpenetrated the polymeric starch matrix and created a fine network of “holes” distributed relatively uniformly in the matrix, which served as additional nucleation sites for expansion. The conclusions of this study can be used in the design of high-quality, fat-free, third-generation snacks.