Structural Properties of Corn-Based Extrudates Enriched with Plant Fibers

Structural properties, such as apparent density, true density, expansion ratio, and porosity, of extruded corn grits enriched with plant fibers were measured. The effect of extrusion conditions, including feed rate (0.7–1.9 g/s), feed moisture content (13–19% wet basis), and extrusion temperature (150–230°C) on structural properties of corn-based extrudates enriched with apple and oat fibers was studied. The ratio of the two fibers to corn flour was ranging from 10 to 30% (fiber/corn). A simple power model was used to correlate porosity with extrusion conditions and material characteristics. Porosity of extrudates was found to decrease with temperature, feed moisture content and fiber to corn ratio, and to increase with feed rate for both the examined fibers. Generally, the addition of fibers led to more dense products. Comparatively, the usage of apple fiber in mixtures for the production of snacks led to a product with higher porosity than those with oat fiber.