THE INFLUENCE OF EXTRUSION CONDITIONS AND PARAMETERS ON THE PROPERTIES OF CORN GRITS EXTRUDATES

Abstract

The article investigated the influence of screw configuration (4:1 and 1:1), moisture content (15% and 20%) and particle size of corn grits on the properties of extrudates. Samples were extruded in a laboratory single screw extruder, at a temperature of 135/170 °C, using a die of a matrix with a diameter of 4 mm. The physical and rheological properties, digestibility and starch damage of the obtained extrudates were determined, then the results were compared with control samples of non-extruded corn grits. Lower moisture content and the use of a screw with a compression ratio of 4: 1 increase the degree of expansion and destructibility, but reduce the bulk density and hardness of the extrudates, regardless of grain size. After the extrusion process, the water absorption index increased, but the peak, hot and cold viscosity of all samples decreased, with a more pronounced effect in cereals extruded with a lower moisture content and with a 4:1 screw. Extrusion caused a decrease in the content of resistant starch and an increase in starch damage in all samples.