Microstructure of an Extruded Third-Generation Snack Made from a Whole Blue Corn and Corn Starch Mixture

Abstract

Blue corn is a potential material for expanded snack production. Whole blue corn meal was mixed with corn starch and processed by extrusion to produce a third-generation snack. Optimum extrusion conditions were calculated with the response surface methodology using expansion index (EI), penetration force (PF), specific mechanical energy (SME) and total anthocyanins content (TAC). Optimum conditions (zone 1, 67°C; cooking zone, 123°C; zone 3, 75°C; feed moisture, 24.6%) were used to extrude the mixture in a single-screw extruder, and EI,PF,SME and TAC of the expanded pellet were compared against predicted optimum values. Starch structural changes in pellets and expanded were analyzed with DSC, viscosity profiles, x-ray diffraction and SEM. Extruded pellet did not differ (p>0.05) from the predicted. However, TAC was lower (p<0.05) in the expanded pellet. Structural analyses showed damage starch granular structure during extrusion and pellet expansion. Blue corn is a promising material for production of third- generation snacks.