14A-22

S. H. Kang and G. H. RYU. Department of Food Science and Technology, Kongju National University, Yesan, 340-800, South Korea

Extrusion with carbon dioxide gas injection was used to improve the processing of the traditional Korean snack (Yukwa). A co-rotating twin screw extruder was used and carbon dioxide gas injection unit was installed on the barrel for formation of bubbles in Yukwa pellet. The screw configuration was high shear and a reverse screw was used to increase residence time of waxy-rice dough in the barrel. The diameter of the die hole was 4 mm. Carbon dioxide cooler, compressor, pressure control valve, reverse screws were installed to control carbon dioxide gas injection pressure. The optimum barrel temperature for good quality of Yukwa was 105^oC and the optimum screw speed was 350 rpm. In comparison to non-carbon dioxide gas injected Yukwa, the carbon dioxide gas injected product had better density and texture. The carbon dioxide gas injected Yukwa had the best quality in conditions of 20-30 rpm feed rate, 105 ^oC barrel temperature, and 350rpm-screw speed, using ground waxy rice steeped for three days. The extruded Yukwa pellets were dried to 17% moisture content and conditioned for 2 days to distribute moisture evenly. This conditioning gave good texture when pellets were fried in oil bath. Extrusion with carbon dioxide gas injection could produce Yukwa pellets which have similar qualities to traditional Yukwa.