**2.5. Corn tortilla preparation**

Two kg of masa from each ENCF were mixed with distilled water to obtain masa. The amount of water was based on the WAC of each extruded treatment. Masas from ENCF were transported to a commercial factory. A roller machine (Rodotec, model RT-100, Guadalupe, N.L., México) was used with a mold of 14 cm diameter, and was adjusted to a masa weight of 25 g. Tortillas were baked in an oven (integrated to the roller machine) with 3 temperature zones: zone 1, 270 ± 10 °C; zone 2, 320 ± 30 °C; and zone 3, 300 ± 25°C, with a residence time of 60 s. The baked tortillas were cooled at room temperature (25 °C).

## **2.6. Corn tortilla textural evaluation**

To determine firmmess and rollability, tortillas packaged in plastic bags were placed at room temperature (25°C). Firmness and rollability were measured at 2 h, 24 h and 48 h after baking. The firmness test was carried out according to the procedure reported by Ramírez-Wong et al. (2007), modifying the cross head speed of the texturometer (Instron, model 4465. Canton, MA, USA) to 50 cm/min. Firmness was expressed as maximal force (MF) in kPa. Regarding tortilla rollability, three strips 2 cm wide were cut from each tortilla and individually tested (Waniska 1976). Each strip of tortilla was rolled up in a wooden cylinder 2 cm in diameter, and was examined for degree of rupture, which was established on a scale of 1 to 5, where 5 indicated no tear of the tortilla (maximum rollability), 3 partial tear, and 1 complete tearing. Five tortillas were used for each treatment in each test.

Viscoelastic and Textural Characteristics of Masa and Tortilla from Extruded Corn Flours with Xanthan Gum 241
