Extrusion of Corn Grits with Native or Modified Starch Addition — Influence on Starch Digestibility Fractions, Shear Stress-at-Break, and Expansion Ratio

The aim of the paper was to seek suitable conditions of extrusion cooking using a laboratory single-screw extruder to increase slowly digestible (SDS) and resistant starch (RS) content in extrudates saving sensory characteristics of the final product prepared from corn grits with added native wheat starch, distarch phosphates, or soluble fibre Nutriose (Roquette, France). In addition to the composition of input mixtures, process parameters of a single-screw extruder, such as speed of screw and barrel temperatures, were changed. The highest expansion ratio (4.14) was found for temperatures 44 °C, 90 °C, 120 °C, and 140 °C, die diameter 3 mm, compression ratio 3:1, rotation speed 140 r.p.m., and dosing 15 r.p.m. The addition of native wheat starch to corn grits resulted in values of the expansion ratio ranging from 1.17–2.38. A high concentration of RS — 2.4% per starch — was observed for a 20% ratio of Nutriose with a 10% addition of water. The addition of 20–50% of native wheat starch resulted in values r...