Abstract
Maize grits with or without starchy additives (native wheat starch, distarch phosphates, soluble fiber) were extruded through a single‐screw laboratory extruder Brabender KE 19/25 with a controlled barrel temperature in three zones and in a head, die diameter 4 mm, comprising a compression ratio of the screw of 2:1. The purpose was to influence resistant starch (RS) content together with improving/saving key physicochemical properties by controlling extrusion cooking variables (water addition into feed of 5–20%, screw speed 80–120 rpm, temperature, mass fraction of the additive in the dry premix 0–50%). The influences of most starchy additives were negligible. Pre‐gelatinized cross‐linked starch and soluble fiber nutriose influenced significantly the process pressure, where a low value exhibited high values RS. Based on the data of 48 trials, 7 mathematical optimization models were computed. High RS content worsened the expansion ratio. To obtain a RS content of 1%, it was necessary to decrease expansion ratio to 1.7 where the breaking strength was acceptable. The result of minimizing resistant starch content created an expansion ratio from 2.6 to 2.7, a breaking strength ≤1 N/mm2 and a RS content (maximum) of 0.2%.
Published Version
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