蒸煮時間對蒸穀糙米物化性質與植酸含量之影響

近年來國人稻米食用量逐年下降，因此開發稻米產品多樣性、提升國人食用稻米的消費量，是本研究的目標之一。糙米的營養價值比白米較高，但糙米亦具有些不利於食用的特性，如：烹煮所需時間較長、含有較多植酸可能影響人體吸收礦物質以及口感較硬。糙米雖然消化性相對白米較低，對於人體血糖反應的影響降低許多，但仍屬於中或高 GI 食品。許多文獻指出蒸穀米具有高完整米率、高營養價值、低病蟲害、較多維生素B1與低GI值等特性。因此本實驗期望了解以不同蒸煮時間處理台南 11 號稻穀，對於蒸穀糙米的物化性質、烹煮性質、食用品質與消化性的影響。實驗結果顯示蒸穀糙米，亮度較暗、顏色偏紅及偏黃，且隨著蒸煮時間增加而更為顯著。糙米植酸含量為 10.57 mg/g，白米植酸含量下降為 8.30 mg/g，浸泡 30 與 60 分鐘之糙米植酸含量沒有減少；蒸煮15與60分鐘的蒸穀糙米植酸含量分別為9.60 mg/g、9.72 mg/g。白米能夠快速吸收較多水份、固形物流失多，米飯長度與體積能膨脹最多；糙米外層具有麩皮阻礙水分吸收，固形物流失、米飯長度與體積膨脹次於白米；不同蒸煮時間的蒸穀糙米水分吸收較少且慢、固形物流失少，米飯長度與體積膨脹率最小。相同水-米比時，糙米經過蒸榖處理硬度提高，黏性下降，並未受蒸煮時間影響。糙米的 eGI (88.70) 與蒸穀糙米的 eGI (85.82-86.64) 相似，糙米與蒸榖糙米有較高的抗性澱粉 (11.72-15.14%)；隨著蒸煮時間增加，蒸穀糙米具有更多的慢速消化澱粉 (49.20-55.60%)。因此糙米經過蒸榖處理可以改善烹煮性質，降低消化性，提供國人食用糙米的另一種形式。

關鍵字

蒸榖糙米；烹煮性質；質地；體外消化試驗

並列摘要

Recently, the production of rice is not change significantly, consumption of rice in Taiwan is declining. Increasing the rice consumption with diversifying rice products is an important issue. Literatures has recognized brown rice to have higher nutrition value than white rice. Brown rice has some disadvantages, such as longer cooking time, higher phytic acid content reduce minerals bioavailability and firm texture. Brown rice yields lower digestibility than white rice and is classified as medium or high GI food. Literatures report parboiled rice has higher head rice yield and nutritional value, and lower GI value. This study was to understand the parboiling effect on the physicochemical properties, cooking properties and digestibility of brown rice. The results showed the color of rice was altered from white to amber after parboiling, and was darker with increasing steaming time. Brown rice (Br) (10.57 mg/g) had more phytic acid than white rice (Wr) (8.30 mg/g). The phytic acid contents of Pr15 (steam 15 min) and Pr60 (steam 60 min) were decrease to 9.60 and 9.72 mg/g respectively. Br, Pr10 (steam 10 min), Pr15 and Pr60 has lower water uptake ratio, lower solids loss, shorter kernel size and lower volume expansion ratio, especially in parboiled brown rice. Pr10, Pr15 has higher hardness and lower adhesiveness than Br and Wr. The eGI value of Br (88.70) is similar to the parboiled brown rice (85.82-86.64). Resistant starch content of Br, Pr15 and Pr60 (11.72-15.14%) are higher than Wr (3.21%). However, slow digestible starch content are increased with increasing steaming time during parboiling process.