射頻乾燥稻穀以製備預煮米之研究

Study of Radio Frequency Drying on Rice Paddy for Preparation of Parboiled Rice

10.6578/TJACFS.202012_58(6).0002

陳淑德(Su-Der Chen)；林季函(Ji-Han Lin)；辛珮琳(Pie-Lin Sin)

稻穀 ； 射頻 ； 乾燥 ； 預煮米 ； Rice paddy ； Radio frequency ； Drying ； Parboiled rice

臺灣農業化學與食品科學

58卷6期（2020 / 12 / 01）

147 - 153

繁體中文

稻穀剛收割時之水分含量約為20～35%，容易發芽及腐敗，必需乾燥於15%以下，以利貯藏。故本研究之目的為建立射頻熱風快速乾燥稻穀操作條件，以達到節能省時的效果，並分析射頻乾燥和45℃冷風乾燥的糙米和精白米之品質。結果顯示稻穀裝載量由1 kg增加至4 kg及縮小電極板間距會提高射頻輸出之功率，射頻乾燥4 kg的濕稻穀的速率可達73 g/min以上，只需10 min內即完成乾燥，且最終溫度高達110℃以上，已有預煮米的效果。在稻穀乾燥的能源消耗方面，射頻乾燥顯著較冷風乾燥為低。比較兩種處理法之糙米與白米，以射頻乾燥的白米顏色較黃，故L*值較低，而a*、b*值較高，而在九分制嗜好性品評中，外觀的喜好性下降，氣味、風味、質地及整體表現則和冷風乾燥的白米無顯著差異，但其射頻乾燥白米之乙醇萃取液之DPPH清除率較高；另外，射頻乾燥糙米之胴裂較小，白米之碎米率較高，直鏈澱粉含量較高，但食味分數較低。整體而言，射頻可應用於稻穀的快速乾燥，並可快速製備預煮米，達到強化營養、減少碾米時破損率和解決儲藏期間發黴及蟲害之問題。

The moisture content of harvested wet paddy rice is about 20~35%, and it is easy to germinate and spoil; therefore, it must be dried to lower than 15% for storage. The objective of this study is to establish the operating conditions for rapid drying of rice by radio frequency (RF) with hot air to achieve both energy and time saving effects, and to analyze the qualities of brown rice and polished white rice by RF drying and 45℃ cold air drying. The results was shown that increasing the rice load from 1 kg to 4 kg and reducing the electrode plate gap will increase the power of the RF output. The RF-hot air drying rate of 4 kg wet paddy rice was 73 g/min to complete drying within 10 min. The final temperature of rice was up to 110℃ to achieve the effect of parboiled rice by steam pre-cooking. The power consumption of drying rice paddy was showed that RF-hot air drying was much lower than cold air drying. Comparing the brown rice and white rice of the two drying methods, the white rice dried by radio frequency had a yellower color, so the L* value was lower, and the a* and b* values were higher. In The 9-point hedonic sensory evaluation, there was no significant difference in odor, flavor, texture and overall performance; however, the ethanol extract from RF white rice had a higher scavenging DPPH power; in addition, the RF dried brown rice has less cracking, and the white rice has a higher broken rice rate, amylose content is higher, but the taste score is lower. Overall, radio frequency can be applied to the rapid drying of rice for direct preparing parboiled rice to achieve enhanced nutrition, reduce the damage rate during rice milling and solve the problems of mold and pests during storage.

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