Sutdies on puffing ratio of dry cooked rice with microwave heating

• Main Authors: Chang, Chih-Chia, 張志嘉
• Other Authors: John-Tung Chien
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/71838166777549672745

碩士 === 輔仁大學 === 食品營養學系 === 84 === Dry cooked rice,being microwave-puffable and ready to eat, was manufactured from polished rice in order to increase its added value and shelf life. The objective of this study was to search the optimal processingconditions on microwavable puffing ratio of the dry cooked rice. TCW70,TC189 and TNuS19 rices which amylose contents were respectively 1.4,18.3 and 25,4% were used. They have been stored for more than six months at 4℃. After beingsteam gelatinized,the rices dehydrated to a water content of 12±1% by two-stepdrying at 90℃ and 70℃. Subsequently, a response surface methodology(RSM) was used to evaluate the effects of rice varieyt, storage time, alcohol and sodium chloride addition on the microwave puffing ratio of the dry cooked rice at 700W for 1 min. The microwave puffing ratio of the dry cooked rice could be increased by extending storage time, adding alcohol or sodium chloride. Among these, addition of sodium chloride was the most effective,the next was addition of alcohol andstorage time was the least effective to the microwave puffing ratio. The optimalconditions for TCW70, TC189 and TNus19 were respectively as follows,alcohol addition of 5.1,4.1,4.2%,sodium chloride addition of 2.9,2.7,3.0%,and storagetime for 20.3,16.6 and 0 day. The rehydration rate(y) of the microwave puffed rices were further analyzed.The rehydration rate could be elucidated by the equation, y=k tN,in which t was the rehydration time, k was the isothermal rehydration rate constant, n was related to the rehydration temperature and the pore structure of the puffed rice. Therehydratuibg rates were increased as the k values increased. It was found that the k values of puffed TCW70 rice at 80℃ were higher than those at 20℃, and both were linearly related to the amounts of sodium chloried added. This was due to the high puffing ratio and the pore structure of the puffed TCW70 rice. The swelling powerfor the fuffed TCW70 rice was higher as compared to both of the puffed TC189 and TNuS19 rices, was likely due to its high amylopectin content.