Changes in Retrogradation Degree of Nonwaxy Rice Cooked at Different Pressure and Stored in Electric Rice Cooker

압력 취반 백미의 전기밥솥 보온중 노화도의 변화

Changes in retrogradation degree of nonwaxy milled rice cooked at different pressure and stored in electric rice cooker at $74^{\circ}C$ were investigated. The moisture contents of nonwaxy milled rice cooked at $1.0{\sim}1.9\;atm\;and\;1.2{\sim}1.5$ water/rice ratio were $59.9{\sim}64.3%$. When nonwaxy milled rice was cooked at high pressure, X-ray diffraction patterns of cooked rice exhibited the V-type having nearly no crystallinity. Retrogradation peak of cooked rice from DSC thermogram was observed in the temperature range of $41.9{\sim}62.4^{\circ}C$ and was not appeared in cooked rice above 1.5 atm. During storage at cooker for 24 hr, retrogradation enthalpy of cooked rice was increased and retrogradation peak was not appeared above 1.7 atm. In cooking and storage of cooked rice, retrogradation degree measured by ${\alpha}-amylase-iodine$ method in high pressure gelatinized samples was lower than that in low pressure gelatinized ones.

압력이 각각 다른 솥에서 취반한 밥의 전기밥솥 보온 중 일어나는 노화 특성을 실험한 결과, $1.0{\sim}1.9$기압의 압력솥에서 $1.2{\sim}1.5$배의 가수량으로 취반하였을 때 밥의 수분함량은 $59.9{\sim}64.3%$로 나타났다. 압력이 높은 솥에서 취반한 밥일수록 X-ray 회절도상에서 결정성이 거의 없는 V도형을 나타내었다. DSC에 의하여 측정했을 때 $41.9{\sim}62.4%$의 범위에서 노화peak가 나타났고, 1.5기압 이상에서 취반한 경우는 peak가 나타나지 않았다. 또한 보온시간이 길어질수록 노화엔탈피는 증가하였으나, 1.7기압 이상에서 취반한 경우는 peak가 나타나지 않았다. ${\alpha}-amylase-iodine$법에 의한 취반직후나 보온 중 밥의 노화도는 고압의 압력솥에서 취반할수록 낮게 나타났다.