Functional, Rheological, Morphological, and Micro‐Structural Properties of Extrusion‐Processed Corn and Potato Starches
Neeraj Gandhi, Baljit Singh, Parminder Singh, Savita Sharma
Abstract
Abstract The purpose of this study is to investigate the effect of twin‐screw extrusion conditions on the properties and quality attributes of corn starch (CS) and potato starch (PS). Extrusion processing conditions used are—feed moisture level of 17% and 18%, screw speed level of 414 and 533 rpm, and barrel temperature of 131 and 135 °C for CS and PS, respectively. When compared with native starches, it is demonstrated that extrusion has a positive effect on the functional properties, that is, bulk density decreases, but water absorption index, water solubility index, degree of gelatinization, and in vitro digestibility increase significantly, and transform its native structure to a honeycomb‐like fine meshwork. Extrusion also results in a significant decrease in pasting temperature, peak viscosity, hold viscosity, final viscosity, breakdown viscosity, and setback viscosity of both the starches. In color profile, a decrease in luminosity, but increase in redness and yellowness are observed in extruded starches. Scanning electron microscopy and X‐ray diffractometry studies show that extrusion leads to complete destruction of structure along with reduced crystallinity and formation of V‐type polymorphs in starches. Compared to CS, PS shows more surface protrusions and formation of air cells leading to formation of a much more microporous structure.