Assessing effect of extrusion processing conditions on colour and viscosity of corn starch using response surface analysis

The investigation explores the effect of extrusion conditions on corn starch using twin screw extruder. Response surface method (RSM) was used to study the effect of feed moisture (14–18%), screw speed (400–550 rpm) and barrel temperature (125–175°C) on colour profile and viscosity of starch. Extrusion processing significantly affected the colour and viscosity of starch. Colour characteristics viz. luminosity, redness and yellowness of corn starch increased with increase in feed moisture and screw speed. The application of high barrel temperature in extruder for production of modified corn starch led to increase in redness and decrease in luminosity and yellowness. The hue angle and chroma values for modified corn starch extrudates ranged between 77.28 to 89.92⁰ and 3.91 to 10.42, respectively. Viscosity decreased after cooking of starch during extrusion. Regression coefficient analysis indicated a lower viscosity with increase in barrel temperature, whereas an increased viscosity with increasing screw speed was observed during processing of corn starch. The study is important for the industry with respect to reformulation and development of products with the desired consistency and improved functional properties.