**3.1.2 Protein**

Limón-Valenzuela et al. (2010) obtained a functional third-generation snack food with good expansion characteristics using a microwave oven, and this snack has health benefits due to the addition of milk protein concentrate ( 0-10%) and quality protein maize ( 20%) in a blend of corn starch (80%). These authors used a laboratory single-extruder with a 3:1 compression ratio, feed moisture (20-30%), a rectangular die, and a central composite non-routable model with two variables

According to the increased demand for new healthy snacks as an alternative for fried starchbased snacks with low nutrient density, Cho & Rizvi (2010) showed the potential of supercritical fluid extrusion (SCFX) technology for healthy snack food production containing high whey protein concentration. SCFX chips had uniform cellular microstructure that cannot be obtained using conventional steam-based extrusion.

Lobato et al. (2011) developed a functional puffed product for extrusion containing 250 g/kg corn starch, 375 g/kg soy flour, and 375 g/kg oat bran extruded under the process conditions of 250 g/kg moisture; 45 g/kg inulin and 130ºC). The puffed product had 212.6 g/kg fiber, 281.0 g/kg protein, and a caloric value of 319.1 kcal/100 g and it was well accepted by the panelists in the sensory evaluation, mainly in terms of texture.
