• Journal of the Korean Society of Food Science and Nutrition
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• v.44 no.8
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• pp.1212-1218
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• 2015

The study was designed to investigate the effects of cold and conventional extrusion on antioxidant properties of extruded rice with vegetables. Moisture content and screw speed were fixed at 25% and 150 rpm. Cold extrusion and conventional extrusion were adjusted at die temperature of $80^{\circ}C$ with a $CO_2$ injection rate of 300 mL/min and $140^{\circ}C$ without a $CO_2$ injection, respectively. Pumpkin, tomato, strawberry, and green tea powder of 10% were individually blended with rice flour. 1,1-Diphenyl-2-picrylhydrazyl radical-scavenging activity of extruded pumpkin and tomato mix by conventional extrusion was higher than that by cold extrusion. Total phenolic content in extruded pumpkin, tomato, and strawberry mix by cold extrusion was higher than that by conventional extrusion. Total flavonoid content was highest (18.82 mg/g) in extruded green tea by conventional extrusion. Total carotenoid content decreased in extruded pumpkin but increased in extruded tomato. Tomato extrudates with cold extrusion had higher lycopene content than conventional extrusion. Anthocyanin content of conventional extruded strawberry was higher than that of cold extrudates. Total chlorophyll contents decreased through the extrusion process.

• Journal of the Korean Society of Food Science and Nutrition
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• v.44 no.6
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• pp.912-920
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• 2015

The study was designed to investigate the effects of die temperature and $CO_2$ injection on the physical and antioxidant properties of extruded rice with tomato flour. Moisture content and screw speed were fixed at 25% and 150 rpm, respectively. Die temperatures and $CO_2$ injection were adjusted to 80, 110, and $140^{\circ}C$ and 0, and 300 mL/min, respectively. Specific mechanical energy input decreased as die temperature increased from 80 to $140^{\circ}C$. The expansion index increased, while bulk density decreased with $CO_2$ injection. All extrudates showed increased water soluble index (WSI) and water absorption index through the extrusion process. WSI increased as die temperature increased. 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity and total phenolic compounds increased as die temperature increased from 80 to $140^{\circ}C$. Total carotenoid and lycopene contents decreased through the extrusion process. Total carotenoid and lycopene contents upon 0 mL/min $CO_2$ injection and $140^{\circ}C$ die temperature were highest at $6.65{\mu}g/g$ and 2.69 mg/kg, respectively. In conclusion, $CO_2$ injection affects expansion properties while an increased die temperature leads to increased DPPH radical scavenging activity and total phenols.