Simultaneous Gelatinization and Drying of Maize Starch in a Single-Screw Extruder

Abstract

Abstract Maize starch (Zea mays) was gelatinized and dried using a jacketed single-screw extruder. The degree of gelatinization (DG), color, swelling properties, solubility, apparent and true densities, expansion ratio, and porosity of extruded maize starch were analyzed. The effects of temperature, feed moisture content, screw speed, and feed rate on the extrusion process and final product properties were also studied. The apparent density of the extruded product was found to increase with an increase in the feed moisture content and residence time, whereas it decreased with an increase in the extrusion temperature. It was observed that the porosity and expansion ratio of the extruded product decreased significantly with increased feed moisture content and residence time. In addition, an increase in temperature led to a product of higher porosity and expansion ratio. Also, the degree of gelatinization increased with an increase in the temperature and screw speed. A correlation was developed for the throughput and specific consumption of mechanical energy for the studied single-screw extruder. Keywords: Color analysisDegree of gelatinizationDrum dryingExpansion ratioPorosityScrew extrusion cookingSwelling and solubility