Hull-less barley flour supplemented corn extrudates produced by conventional extrusion and CO2 injection process

The effects of feed moisture content (20, 25%), exit–die temperature (80, 130 °C), and extrusion-cooking method (with/without CO₂ injection) on β-glucan (BG) levels and physicochemical properties of hull-less barley flour (HBF) supplemented (15, 30, 45%) corn extrudates were investigated. The highest HBF supplementation level (45%) resulted in higher BG levels (2.87–3.28%) in all extrusion conditions. In general, increasing feed moisture content from 20 to 25% and exit–die temperature from 80 to 130 °C resulted in small increases in enzyme resistant starch type-3 (RS₃) levels. However, the investigated extrusion conditions did not form substantial amount of RS₃ and the highest RS₃ content was 540 mg/100 g. Lower feed moisture content and higher exit–die temperature resulted in higher water solubility (WS) and lower water-binding capacity (WBC) values. Cold-paste viscosity (CV) was observed in all extrudates. High WS and WBC values of extrudates and the existence of CV values in RVA curves indicated complete starch gelatinization.Industrial relevanceCO₂ injection has been proved as a reliable alternative method to the conventional extrusion process used in the breakfast cereals and snack food industry. The overall quality of the product processed by CO₂ injection was comparable to that of the current process. The extrudates produced by CO₂ injection method had more uniform expansion and smoother surface. CO₂ injection did not have a reducing effect on β-glucan levels; however, it is expected to result in a better retention of heat labile micronutrients and hence more healthy food products.